python-peps/docutils/parsers/rst/states.py

# Author: David Goodger
# Contact: goodger@users.sourceforge.net
# Revision: $Revision$
# Date: $Date$
# Copyright: This module has been placed in the public domain.

"""
This is the ``docutils.parsers.restructuredtext.states`` module, the core of
the reStructuredText parser.  It defines the following:

:Classes:
    - `RSTStateMachine`: reStructuredText parser's entry point.
    - `NestedStateMachine`: recursive StateMachine.
    - `RSTState`: reStructuredText State superclass.
    - `Inliner`: For parsing inline markup.
    - `Body`: Generic classifier of the first line of a block.
    - `SpecializedBody`: Superclass for compound element members.
    - `BulletList`: Second and subsequent bullet_list list_items
    - `DefinitionList`: Second+ definition_list_items.
    - `EnumeratedList`: Second+ enumerated_list list_items.
    - `FieldList`: Second+ fields.
    - `OptionList`: Second+ option_list_items.
    - `RFC2822List`: Second+ RFC2822-style fields.
    - `ExtensionOptions`: Parses directive option fields.
    - `Explicit`: Second+ explicit markup constructs.
    - `SubstitutionDef`: For embedded directives in substitution definitions.
    - `Text`: Classifier of second line of a text block.
    - `SpecializedText`: Superclass for continuation lines of Text-variants.
    - `Definition`: Second line of potential definition_list_item.
    - `Line`: Second line of overlined section title or transition marker.
    - `Struct`: An auxiliary collection class.

:Exception classes:
    - `MarkupError`
    - `ParserError`
    - `MarkupMismatch`

:Functions:
    - `escape2null()`: Return a string, escape-backslashes converted to nulls.
    - `unescape()`: Return a string, nulls removed or restored to backslashes.

:Attributes:
    - `state_classes`: set of State classes used with `RSTStateMachine`.

Parser Overview
===============

The reStructuredText parser is implemented as a recursive state machine,
examining its input one line at a time.  To understand how the parser works,
please first become familiar with the `docutils.statemachine` module.  In the
description below, references are made to classes defined in this module;
please see the individual classes for details.

Parsing proceeds as follows:

1. The state machine examines each line of input, checking each of the
   transition patterns of the state `Body`, in order, looking for a match.
   The implicit transitions (blank lines and indentation) are checked before
   any others.  The 'text' transition is a catch-all (matches anything).

2. The method associated with the matched transition pattern is called.

   A. Some transition methods are self-contained, appending elements to the
      document tree (`Body.doctest` parses a doctest block).  The parser's
      current line index is advanced to the end of the element, and parsing
      continues with step 1.

   B. Other transition methods trigger the creation of a nested state machine,
      whose job is to parse a compound construct ('indent' does a block quote,
      'bullet' does a bullet list, 'overline' does a section [first checking
      for a valid section header], etc.).

      - In the case of lists and explicit markup, a one-off state machine is
        created and run to parse contents of the first item.

      - A new state machine is created and its initial state is set to the
        appropriate specialized state (`BulletList` in the case of the
        'bullet' transition; see `SpecializedBody` for more detail).  This
        state machine is run to parse the compound element (or series of
        explicit markup elements), and returns as soon as a non-member element
        is encountered.  For example, the `BulletList` state machine ends as
        soon as it encounters an element which is not a list item of that
        bullet list.  The optional omission of inter-element blank lines is
        enabled by this nested state machine.

      - The current line index is advanced to the end of the elements parsed,
        and parsing continues with step 1.

   C. The result of the 'text' transition depends on the next line of text.
      The current state is changed to `Text`, under which the second line is
      examined.  If the second line is:

      - Indented: The element is a definition list item, and parsing proceeds
        similarly to step 2.B, using the `DefinitionList` state.

      - A line of uniform punctuation characters: The element is a section
        header; again, parsing proceeds as in step 2.B, and `Body` is still
        used.

      - Anything else: The element is a paragraph, which is examined for
        inline markup and appended to the parent element.  Processing
        continues with step 1.
"""

__docformat__ = 'reStructuredText'


import sys
import re
from types import TupleType
from docutils import nodes, statemachine, utils, roman, urischemes
from docutils import ApplicationError, DataError
from docutils.statemachine import StateMachineWS, StateWS
from docutils.utils import normalize_name
from docutils.parsers.rst import directives, languages, tableparser


class MarkupError(DataError): pass
class ParserError(ApplicationError): pass
class MarkupMismatch(Exception): pass


class Struct:

    """Stores data attributes for dotted-attribute access."""

    def __init__(self, **keywordargs):
        self.__dict__.update(keywordargs)


class RSTStateMachine(StateMachineWS):

    """
    reStructuredText's master StateMachine.

    The entry point to reStructuredText parsing is the `run()` method.
    """

    def run(self, input_lines, document, input_offset=0, match_titles=1,
            inliner=None):
        """
        Parse `input_lines` and return a `docutils.nodes.document` instance.

        Extend `StateMachineWS.run()`: set up parse-global data, run the
        StateMachine, and return the resulting
        document.
        """
        self.language = languages.get_language(
            document.settings.language_code)
        self.match_titles = match_titles
        if inliner is None:
            inliner = Inliner()
        inliner.init_customizations(document.settings)
        self.memo = Struct(document=document,
                           reporter=document.reporter,
                           language=self.language,
                           title_styles=[],
                           section_level=0,
                           inliner=inliner)
        self.document = document
        self.attach_observer(document.note_source)
        self.reporter = self.memo.reporter
        self.node = document
        results = StateMachineWS.run(self, input_lines, input_offset,
                                     input_source=document['source'])
        assert results == [], 'RSTStateMachine.run() results should be empty!'
        self.check_document()
        self.node = self.memo = None    # remove unneeded references

    def check_document(self):
        """Check for illegal structure: empty document."""
        if len(self.document) == 0:
            error = self.reporter.error(
                'Document empty; must have contents.', line=0)
            self.document += error


class NestedStateMachine(StateMachineWS):

    """
    StateMachine run from within other StateMachine runs, to parse nested
    document structures.
    """

    def run(self, input_lines, input_offset, memo, node, match_titles=1):
        """
        Parse `input_lines` and populate a `docutils.nodes.document` instance.

        Extend `StateMachineWS.run()`: set up document-wide data.
        """
        self.match_titles = match_titles
        self.memo = memo
        self.document = memo.document
        self.attach_observer(self.document.note_source)
        self.reporter = memo.reporter
        self.node = node
        results = StateMachineWS.run(self, input_lines, input_offset)
        assert results == [], ('NestedStateMachine.run() results should be '
                               'empty!')
        return results


class RSTState(StateWS):

    """
    reStructuredText State superclass.

    Contains methods used by all State subclasses.
    """

    nested_sm = NestedStateMachine

    def __init__(self, state_machine, debug=0):
        self.nested_sm_kwargs = {'state_classes': state_classes,
                                 'initial_state': 'Body'}
        StateWS.__init__(self, state_machine, debug)

    def runtime_init(self):
        StateWS.runtime_init(self)
        memo = self.state_machine.memo
        self.memo = memo
        self.reporter = memo.reporter
        self.inliner = memo.inliner
        self.document = memo.document
        self.parent = self.state_machine.node

    def goto_line(self, abs_line_offset):
        """
        Jump to input line `abs_line_offset`, ignoring jumps past the end.
        """
        try:
            self.state_machine.goto_line(abs_line_offset)
        except EOFError:
            pass

    def no_match(self, context, transitions):
        """
        Override `StateWS.no_match` to generate a system message.

        This code should never be run.
        """
        self.reporter.severe(
            'Internal error: no transition pattern match.  State: "%s"; '
            'transitions: %s; context: %s; current line: %r.'
            % (self.__class__.__name__, transitions, context,
               self.state_machine.line),
            line=self.state_machine.abs_line_number())
        return context, None, []

    def bof(self, context):
        """Called at beginning of file."""
        return [], []

    def nested_parse(self, block, input_offset, node, match_titles=0,
                     state_machine_class=None, state_machine_kwargs=None):
        """
        Create a new StateMachine rooted at `node` and run it over the input
        `block`.
        """
        if state_machine_class is None:
            state_machine_class = self.nested_sm
        if state_machine_kwargs is None:
            state_machine_kwargs = self.nested_sm_kwargs
        block_length = len(block)
        state_machine = state_machine_class(debug=self.debug,
                                            **state_machine_kwargs)
        state_machine.run(block, input_offset, memo=self.memo,
                          node=node, match_titles=match_titles)
        state_machine.unlink()
        new_offset = state_machine.abs_line_offset()
        # Adjustment for block if modified in nested parse:
        self.state_machine.next_line(len(block) - block_length)
        return new_offset

    def nested_list_parse(self, block, input_offset, node, initial_state,
                          blank_finish,
                          blank_finish_state=None,
                          extra_settings={},
                          match_titles=0,
                          state_machine_class=None,
                          state_machine_kwargs=None):
        """
        Create a new StateMachine rooted at `node` and run it over the input
        `block`. Also keep track of optional intermdediate blank lines and the
        required final one.
        """
        if state_machine_class is None:
            state_machine_class = self.nested_sm
        if state_machine_kwargs is None:
            state_machine_kwargs = self.nested_sm_kwargs.copy()
        state_machine_kwargs['initial_state'] = initial_state
        state_machine = state_machine_class(debug=self.debug,
                                            **state_machine_kwargs)
        if blank_finish_state is None:
            blank_finish_state = initial_state
        state_machine.states[blank_finish_state].blank_finish = blank_finish
        for key, value in extra_settings.items():
            setattr(state_machine.states[initial_state], key, value)
        state_machine.run(block, input_offset, memo=self.memo,
                          node=node, match_titles=match_titles)
        blank_finish = state_machine.states[blank_finish_state].blank_finish
        state_machine.unlink()
        return state_machine.abs_line_offset(), blank_finish

    def section(self, title, source, style, lineno, messages):
        """Check for a valid subsection and create one if it checks out."""
        if self.check_subsection(source, style, lineno):
            self.new_subsection(title, lineno, messages)

    def check_subsection(self, source, style, lineno):
        """
        Check for a valid subsection header.  Return 1 (true) or None (false).

        When a new section is reached that isn't a subsection of the current
        section, back up the line count (use ``previous_line(-x)``), then
        ``raise EOFError``.  The current StateMachine will finish, then the
        calling StateMachine can re-examine the title.  This will work its way
        back up the calling chain until the correct section level isreached.

        @@@ Alternative: Evaluate the title, store the title info & level, and
        back up the chain until that level is reached.  Store in memo? Or
        return in results?

        :Exception: `EOFError` when a sibling or supersection encountered.
        """
        memo = self.memo
        title_styles = memo.title_styles
        mylevel = memo.section_level
        try:                            # check for existing title style
            level = title_styles.index(style) + 1
        except ValueError:              # new title style
            if len(title_styles) == memo.section_level: # new subsection
                title_styles.append(style)
                return 1
            else:                       # not at lowest level
                self.parent += self.title_inconsistent(source, lineno)
                return None
        if level <= mylevel:            # sibling or supersection
            memo.section_level = level   # bubble up to parent section
            # back up 2 lines for underline title, 3 for overline title
            self.state_machine.previous_line(len(style) + 1)
            raise EOFError              # let parent section re-evaluate
        if level == mylevel + 1:        # immediate subsection
            return 1
        else:                           # invalid subsection
            self.parent += self.title_inconsistent(source, lineno)
            return None

    def title_inconsistent(self, sourcetext, lineno):
        error = self.reporter.severe(
            'Title level inconsistent:', nodes.literal_block('', sourcetext),
            line=lineno)
        return error

    def new_subsection(self, title, lineno, messages):
        """Append new subsection to document tree. On return, check level."""
        memo = self.memo
        mylevel = memo.section_level
        memo.section_level += 1
        section_node = nodes.section()
        self.parent += section_node
        textnodes, title_messages = self.inline_text(title, lineno)
        titlenode = nodes.title(title, '', *textnodes)
        name = normalize_name(titlenode.astext())
        section_node['name'] = name
        section_node += titlenode
        section_node += messages
        section_node += title_messages
        self.document.note_implicit_target(section_node, section_node)
        offset = self.state_machine.line_offset + 1
        absoffset = self.state_machine.abs_line_offset() + 1
        newabsoffset = self.nested_parse(
              self.state_machine.input_lines[offset:], input_offset=absoffset,
              node=section_node, match_titles=1)
        self.goto_line(newabsoffset)
        self.check_section(section_node)
        if memo.section_level <= mylevel: # can't handle next section?
            raise EOFError              # bubble up to supersection
        # reset section_level; next pass will detect it properly
        memo.section_level = mylevel

    def check_section(self, section):
        """
        Check for illegal structure: empty section, misplaced transitions.
        """
        lineno = section.line
        if len(section) <= 1:
            error = self.reporter.error(
                'Section empty; must have contents.', line=lineno)
            section += error
            return
        if not isinstance(section[0], nodes.title): # shouldn't ever happen
            error = self.reporter.error(
                'First element of section must be a title.', line=lineno)
            section.insert(0, error)
        if isinstance(section[1], nodes.transition):
            error = self.reporter.error(
                'Section may not begin with a transition.',
                line=section[1].line)
            section.insert(1, error)
        if len(section) > 2 and isinstance(section[-1], nodes.transition):
            error = self.reporter.error(
                'Section may not end with a transition.',
                line=section[-1].line)
            section += error

    def paragraph(self, lines, lineno):
        """
        Return a list (paragraph & messages) & a boolean: literal_block next?
        """
        data = '\n'.join(lines).rstrip()
        if data[-2:] == '::':
            if len(data) == 2:
                return [], 1
            elif data[-3] in ' \n':
                text = data[:-3].rstrip()
            else:
                text = data[:-1]
            literalnext = 1
        else:
            text = data
            literalnext = 0
        textnodes, messages = self.inline_text(text, lineno)
        p = nodes.paragraph(data, '', *textnodes)
        p.line = lineno
        return [p] + messages, literalnext

    def inline_text(self, text, lineno):
        """
        Return 2 lists: nodes (text and inline elements), and system_messages.
        """
        return self.inliner.parse(text, lineno, self.memo, self.parent)

    def unindent_warning(self, node_name):
        return self.reporter.warning(
            '%s ends without a blank line; unexpected unindent.' % node_name,
            line=(self.state_machine.abs_line_number() + 1))


def build_regexp(definition, compile=1):
    """
    Build, compile and return a regular expression based on `definition`.

    :Parameter: `definition`: a 4-tuple (group name, prefix, suffix, parts),
        where "parts" is a list of regular expressions and/or regular
        expression definitions to be joined into an or-group.
    """
    name, prefix, suffix, parts = definition
    part_strings = []
    for part in parts:
        if type(part) is TupleType:
            part_strings.append(build_regexp(part, None))
        else:
            part_strings.append(part)
    or_group = '|'.join(part_strings)
    regexp = '%(prefix)s(?P<%(name)s>%(or_group)s)%(suffix)s' % locals()
    if compile:
        return re.compile(regexp, re.UNICODE)
    else:
        return regexp


class Inliner:

    """
    Parse inline markup; call the `parse()` method.
    """

    def __init__(self):
        self.implicit_dispatch = [(self.patterns.uri, self.standalone_uri),]
        """List of (pattern, bound method) tuples, used by
        `self.implicit_inline`."""

    def init_customizations(self, settings):
        """Setting-based customizations; run when parsing begins."""
        if settings.pep_references:
            self.implicit_dispatch.append((self.patterns.pep,
                                           self.pep_reference))
        if settings.rfc_references:
            self.implicit_dispatch.append((self.patterns.rfc,
                                           self.rfc_reference))

    def parse(self, text, lineno, memo, parent):
        """
        Return 2 lists: nodes (text and inline elements), and system_messages.

        Using `self.patterns.initial`, a pattern which matches start-strings
        (emphasis, strong, interpreted, phrase reference, literal,
        substitution reference, and inline target) and complete constructs
        (simple reference, footnote reference), search for a candidate.  When
        one is found, check for validity (e.g., not a quoted '*' character).
        If valid, search for the corresponding end string if applicable, and
        check it for validity.  If not found or invalid, generate a warning
        and ignore the start-string.  Implicit inline markup (e.g. standalone
        URIs) is found last.
        """
        self.reporter = memo.reporter
        self.document = memo.document
        self.parent = parent
        pattern_search = self.patterns.initial.search
        dispatch = self.dispatch
        remaining = escape2null(text)
        processed = []
        unprocessed = []
        messages = []
        while remaining:
            match = pattern_search(remaining)
            if match:
                groups = match.groupdict()
                method = dispatch[groups['start'] or groups['backquote']
                                  or groups['refend'] or groups['fnend']]
                before, inlines, remaining, sysmessages = method(self, match,
                                                                 lineno)
                unprocessed.append(before)
                messages += sysmessages
                if inlines:
                    processed += self.implicit_inline(''.join(unprocessed),
                                                      lineno)
                    processed += inlines
                    unprocessed = []
            else:
                break
        remaining = ''.join(unprocessed) + remaining
        if remaining:
            processed += self.implicit_inline(remaining, lineno)
        return processed, messages

    openers = '\'"([{<'
    closers = '\'")]}>'
    start_string_prefix = (r'((?<=^)|(?<=[-/: \n%s]))' % re.escape(openers))
    end_string_suffix = (r'((?=$)|(?=[-/:.,;!? \n\x00%s]))' % re.escape(closers))
    non_whitespace_before = r'(?<![ \n])'
    non_whitespace_escape_before = r'(?<![ \n\x00])'
    non_whitespace_after = r'(?![ \n])'
    # Alphanumerics with isolated internal [-._] chars (i.e. not 2 together):
    simplename = r'(?:(?!_)\w)+(?:[-._](?:(?!_)\w)+)*'
    # Valid URI characters (see RFC 2396 & RFC 2732):
    uric = r"""[-_.!~*'()[\];/:@&=+$,%a-zA-Z0-9]"""
    # Last URI character; same as uric but no punctuation:
    urilast = r"""[_~/a-zA-Z0-9]"""
    emailc = r"""[-_!~*'{|}/#?^`&=+$%a-zA-Z0-9]"""
    email_pattern = r"""
          %(emailc)s+(?:\.%(emailc)s+)*   # name
          @                               # at
          %(emailc)s+(?:\.%(emailc)s*)*   # host
          %(urilast)s                     # final URI char
          """
    parts = ('initial_inline', start_string_prefix, '',
             [('start', '', non_whitespace_after,  # simple start-strings
               [r'\*\*',                # strong
                r'\*(?!\*)',            # emphasis but not strong
                r'``',                  # literal
                r'_`',                  # inline internal target
                r'\|(?!\|)']            # substitution reference
               ),
              ('whole', '', end_string_suffix, # whole constructs
               [# reference name & end-string
                r'(?P<refname>%s)(?P<refend>__?)' % simplename,
                ('footnotelabel', r'\[', r'(?P<fnend>\]_)',
                 [r'[0-9]+',               # manually numbered
                  r'\#(%s)?' % simplename, # auto-numbered (w/ label?)
                  r'\*',                   # auto-symbol
                  r'(?P<citationlabel>%s)' % simplename] # citation reference
                 )
                ]
               ),
              ('backquote',             # interpreted text or phrase reference
               '(?P<role>(:%s:)?)' % simplename, # optional role
               non_whitespace_after,
               ['`(?!`)']               # but not literal
               )
              ]
             )
    patterns = Struct(
          initial=build_regexp(parts),
          emphasis=re.compile(non_whitespace_escape_before
                              + r'(\*)' + end_string_suffix),
          strong=re.compile(non_whitespace_escape_before
                            + r'(\*\*)' + end_string_suffix),
          interpreted_or_phrase_ref=re.compile(
              r"""
              %(non_whitespace_escape_before)s
              (
                `
                (?P<suffix>
                  (?P<role>:%(simplename)s:)?
                  (?P<refend>__?)?
                )
              )
              %(end_string_suffix)s
              """ % locals(), re.VERBOSE | re.UNICODE),
          embedded_uri=re.compile(
              r"""
              (
                [ \n]+                  # spaces or beginning of line
                <                       # open bracket
                %(non_whitespace_after)s
                ([^<>\0]+)              # anything but angle brackets & nulls
                %(non_whitespace_before)s
                >                       # close bracket w/o whitespace before
              )
              $                         # end of string
              """ % locals(), re.VERBOSE),
          literal=re.compile(non_whitespace_before + '(``)'
                             + end_string_suffix),
          target=re.compile(non_whitespace_escape_before
                            + r'(`)' + end_string_suffix),
          substitution_ref=re.compile(non_whitespace_escape_before
                                      + r'(\|_{0,2})'
                                      + end_string_suffix),
          email=re.compile(email_pattern % locals() + '$', re.VERBOSE),
          uri=re.compile(
                (r"""
                %(start_string_prefix)s
                (?P<whole>
                  (?P<absolute>           # absolute URI
                    (?P<scheme>             # scheme (http, ftp, mailto)
                      [a-zA-Z][a-zA-Z0-9.+-]*
                    )
                    :
                    (
                      (                       # either:
                        (//?)?                  # hierarchical URI
                        %(uric)s*               # URI characters
                        %(urilast)s             # final URI char
                      )
                      (                       # optional query
                        \?%(uric)s*
                        %(urilast)s
                      )?
                      (                       # optional fragment
                        \#%(uric)s*
                        %(urilast)s
                      )?
                    )
                  )
                |                       # *OR*
                  (?P<email>              # email address
                    """ + email_pattern + r"""
                  )
                )
                %(end_string_suffix)s
                """) % locals(), re.VERBOSE),
          pep=re.compile(
                r"""
                %(start_string_prefix)s
                (
                  (pep-(?P<pepnum1>\d+)(.txt)?) # reference to source file
                |
                  (PEP\s+(?P<pepnum2>\d+))      # reference by name
                )
                %(end_string_suffix)s""" % locals(), re.VERBOSE),
          rfc=re.compile(
                r"""
                %(start_string_prefix)s
                (RFC(-|\s+)?(?P<rfcnum>\d+))
                %(end_string_suffix)s""" % locals(), re.VERBOSE))

    def quoted_start(self, match):
        """Return 1 if inline markup start-string is 'quoted', 0 if not."""
        string = match.string
        start = match.start()
        end = match.end()
        if start == 0:                  # start-string at beginning of text
            return 0
        prestart = string[start - 1]
        try:
            poststart = string[end]
            if self.openers.index(prestart) \
                  == self.closers.index(poststart):   # quoted
                return 1
        except IndexError:              # start-string at end of text
            return 1
        except ValueError:              # not quoted
            pass
        return 0

    def inline_obj(self, match, lineno, end_pattern, nodeclass,
                   restore_backslashes=0):
        string = match.string
        matchstart = match.start('start')
        matchend = match.end('start')
        if self.quoted_start(match):
            return (string[:matchend], [], string[matchend:], [], '')
        endmatch = end_pattern.search(string[matchend:])
        if endmatch and endmatch.start(1):  # 1 or more chars
            text = unescape(endmatch.string[:endmatch.start(1)],
                            restore_backslashes)
            textend = matchend + endmatch.end(1)
            rawsource = unescape(string[matchstart:textend], 1)
            return (string[:matchstart], [nodeclass(rawsource, text)],
                    string[textend:], [], endmatch.group(1))
        msg = self.reporter.warning(
              'Inline %s start-string without end-string.'
              % nodeclass.__name__, line=lineno)
        text = unescape(string[matchstart:matchend], 1)
        rawsource = unescape(string[matchstart:matchend], 1)
        prb = self.problematic(text, rawsource, msg)
        return string[:matchstart], [prb], string[matchend:], [msg], ''

    def problematic(self, text, rawsource, message):
        msgid = self.document.set_id(message, self.parent)
        problematic = nodes.problematic(rawsource, text, refid=msgid)
        prbid = self.document.set_id(problematic)
        message.add_backref(prbid)
        return problematic

    def emphasis(self, match, lineno):
        before, inlines, remaining, sysmessages, endstring = self.inline_obj(
              match, lineno, self.patterns.emphasis, nodes.emphasis)
        return before, inlines, remaining, sysmessages

    def strong(self, match, lineno):
        before, inlines, remaining, sysmessages, endstring = self.inline_obj(
              match, lineno, self.patterns.strong, nodes.strong)
        return before, inlines, remaining, sysmessages

    def interpreted_or_phrase_ref(self, match, lineno):
        end_pattern = self.patterns.interpreted_or_phrase_ref
        string = match.string
        matchstart = match.start('backquote')
        matchend = match.end('backquote')
        rolestart = match.start('role')
        role = match.group('role')
        position = ''
        if role:
            role = role[1:-1]
            position = 'prefix'
        elif self.quoted_start(match):
            return (string[:matchend], [], string[matchend:], [])
        endmatch = end_pattern.search(string[matchend:])
        if endmatch and endmatch.start(1):  # 1 or more chars
            textend = matchend + endmatch.end()
            if endmatch.group('role'):
                if role:
                    msg = self.reporter.warning(
                        'Multiple roles in interpreted text (both '
                        'prefix and suffix present; only one allowed).',
                        line=lineno)
                    text = unescape(string[rolestart:textend], 1)
                    prb = self.problematic(text, text, msg)
                    return string[:rolestart], [prb], string[textend:], [msg]
                role = endmatch.group('suffix')[1:-1]
                position = 'suffix'
            escaped = endmatch.string[:endmatch.start(1)]
            text = unescape(escaped, 0)
            rawsource = unescape(string[matchstart:textend], 1)
            if rawsource[-1:] == '_':
                if role:
                    msg = self.reporter.warning(
                          'Mismatch: both interpreted text role %s and '
                          'reference suffix.' % position, line=lineno)
                    text = unescape(string[rolestart:textend], 1)
                    prb = self.problematic(text, text, msg)
                    return string[:rolestart], [prb], string[textend:], [msg]
                return self.phrase_ref(string[:matchstart], string[textend:],
                                       rawsource, escaped, text)
            else:
                return self.interpreted(string[:rolestart], string[textend:],
                                        rawsource, text, role, position)
        msg = self.reporter.warning(
              'Inline interpreted text or phrase reference start-string '
              'without end-string.', line=lineno)
        text = unescape(string[matchstart:matchend], 1)
        prb = self.problematic(text, text, msg)
        return string[:matchstart], [prb], string[matchend:], [msg]

    def phrase_ref(self, before, after, rawsource, escaped, text):
        match = self.patterns.embedded_uri.search(escaped)
        if match:
            text = unescape(escaped[:match.start(0)])
            uri_text = match.group(2)
            uri = ''.join(uri_text.split())
            uri = self.adjust_uri(uri)
            if uri:
                target = nodes.target(match.group(1), refuri=uri)
            else:
                raise ApplicationError('problem with URI: %r' % uri_text)
        else:
            target = None
        refname = normalize_name(text)
        reference = nodes.reference(rawsource, text)
        node_list = [reference]
        if rawsource[-2:] == '__':
            if target:
                reference['refuri'] = uri
            else:
                reference['anonymous'] = 1
                self.document.note_anonymous_ref(reference)
        else:
            if target:
                reference['refuri'] = uri
                target['name'] = refname
                self.document.note_external_target(target)
                self.document.note_explicit_target(target, self.parent)
                node_list.append(target)
            else:
                reference['refname'] = refname
                self.document.note_refname(reference)
        return before, node_list, after, []

    def adjust_uri(self, uri):
        match = self.patterns.email.match(uri)
        if match:
            return 'mailto:' + uri
        else:
            return uri

    def interpreted(self, before, after, rawsource, text, role, position):
        if role:
            atts = {'role': role, 'position': position}
        else:
            atts = {}
        return before, [nodes.interpreted(rawsource, text, **atts)], after, []

    def literal(self, match, lineno):
        before, inlines, remaining, sysmessages, endstring = self.inline_obj(
              match, lineno, self.patterns.literal, nodes.literal,
              restore_backslashes=1)
        return before, inlines, remaining, sysmessages

    def inline_internal_target(self, match, lineno):
        before, inlines, remaining, sysmessages, endstring = self.inline_obj(
              match, lineno, self.patterns.target, nodes.target)
        if inlines and isinstance(inlines[0], nodes.target):
            assert len(inlines) == 1
            target = inlines[0]
            name = normalize_name(target.astext())
            target['name'] = name
            self.document.note_explicit_target(target, self.parent)
        return before, inlines, remaining, sysmessages

    def substitution_reference(self, match, lineno):
        before, inlines, remaining, sysmessages, endstring = self.inline_obj(
              match, lineno, self.patterns.substitution_ref,
              nodes.substitution_reference)
        if len(inlines) == 1:
            subrefnode = inlines[0]
            if isinstance(subrefnode, nodes.substitution_reference):
                subreftext = subrefnode.astext()
                refname = normalize_name(subreftext)
                subrefnode['refname'] = refname
                self.document.note_substitution_ref(
                      subrefnode)
                if endstring[-1:] == '_':
                    referencenode = nodes.reference(
                          '|%s%s' % (subreftext, endstring), '')
                    if endstring[-2:] == '__':
                        referencenode['anonymous'] = 1
                        self.document.note_anonymous_ref(
                              referencenode)
                    else:
                        referencenode['refname'] = refname
                        self.document.note_refname(
                              referencenode)
                    referencenode += subrefnode
                    inlines = [referencenode]
        return before, inlines, remaining, sysmessages

    def footnote_reference(self, match, lineno):
        """
        Handles `nodes.footnote_reference` and `nodes.citation_reference`
        elements.
        """
        label = match.group('footnotelabel')
        refname = normalize_name(label)
        if match.group('citationlabel'):
            refnode = nodes.citation_reference('[%s]_' % label,
                                               refname=refname)
            refnode += nodes.Text(label)
            self.document.note_citation_ref(refnode)
        else:
            refnode = nodes.footnote_reference('[%s]_' % label)
            if refname[0] == '#':
                refname = refname[1:]
                refnode['auto'] = 1
                self.document.note_autofootnote_ref(refnode)
            elif refname == '*':
                refname = ''
                refnode['auto'] = '*'
                self.document.note_symbol_footnote_ref(
                      refnode)
            else:
                refnode += nodes.Text(label)
            if refname:
                refnode['refname'] = refname
                self.document.note_footnote_ref(refnode)
        string = match.string
        matchstart = match.start('whole')
        matchend = match.end('whole')
        return (string[:matchstart], [refnode], string[matchend:], [])

    def reference(self, match, lineno, anonymous=None):
        referencename = match.group('refname')
        refname = normalize_name(referencename)
        referencenode = nodes.reference(referencename + match.group('refend'),
                                        referencename)
        if anonymous:
            referencenode['anonymous'] = 1
            self.document.note_anonymous_ref(referencenode)
        else:
            referencenode['refname'] = refname
            self.document.note_refname(referencenode)
        string = match.string
        matchstart = match.start('whole')
        matchend = match.end('whole')
        return (string[:matchstart], [referencenode], string[matchend:], [])

    def anonymous_reference(self, match, lineno):
        return self.reference(match, lineno, anonymous=1)

    def standalone_uri(self, match, lineno):
        if not match.group('scheme') or urischemes.schemes.has_key(
              match.group('scheme').lower()):
            if match.group('email'):
                addscheme = 'mailto:'
            else:
                addscheme = ''
            text = match.group('whole')
            unescaped = unescape(text, 0)
            return [nodes.reference(unescape(text, 1), unescaped,
                                    refuri=addscheme + unescaped)]
        else:                   # not a valid scheme
            raise MarkupMismatch

    pep_url_local = 'pep-%04d.html'
    pep_url_absolute = 'http://www.python.org/peps/pep-%04d.html'
    pep_url = pep_url_absolute

    def pep_reference(self, match, lineno):
        text = match.group(0)
        if text.startswith('pep-'):
            pepnum = int(match.group('pepnum1'))
        elif text.startswith('PEP'):
            pepnum = int(match.group('pepnum2'))
        else:
            raise MarkupMismatch
        ref = self.pep_url % pepnum
        unescaped = unescape(text, 0)
        return [nodes.reference(unescape(text, 1), unescaped, refuri=ref)]

    rfc_url = 'http://www.faqs.org/rfcs/rfc%d.html'

    def rfc_reference(self, match, lineno):
        text = match.group(0)
        if text.startswith('RFC'):
            rfcnum = int(match.group('rfcnum'))
            ref = self.rfc_url % rfcnum
        else:
            raise MarkupMismatch
        unescaped = unescape(text, 0)
        return [nodes.reference(unescape(text, 1), unescaped, refuri=ref)]

    def implicit_inline(self, text, lineno):
        """
        Check each of the patterns in `self.implicit_dispatch` for a match,
        and dispatch to the stored method for the pattern.  Recursively check
        the text before and after the match.  Return a list of `nodes.Text`
        and inline element nodes.
        """
        if not text:
            return []
        for pattern, method in self.implicit_dispatch:
            match = pattern.search(text)
            if match:
                try:
                    # Must recurse on strings before *and* after the match;
                    # there may be multiple patterns.
                    return (self.implicit_inline(text[:match.start()], lineno)
                            + method(match, lineno) +
                            self.implicit_inline(text[match.end():], lineno))
                except MarkupMismatch:
                    pass
        return [nodes.Text(unescape(text), rawsource=unescape(text, 1))]

    dispatch = {'*': emphasis,
                '**': strong,
                '`': interpreted_or_phrase_ref,
                '``': literal,
                '_`': inline_internal_target,
                ']_': footnote_reference,
                '|': substitution_reference,
                '_': reference,
                '__': anonymous_reference}


class Body(RSTState):

    """
    Generic classifier of the first line of a block.
    """

    enum = Struct()
    """Enumerated list parsing information."""

    enum.formatinfo = {
          'parens': Struct(prefix='(', suffix=')', start=1, end=-1),
          'rparen': Struct(prefix='', suffix=')', start=0, end=-1),
          'period': Struct(prefix='', suffix='.', start=0, end=-1)}
    enum.formats = enum.formatinfo.keys()
    enum.sequences = ['arabic', 'loweralpha', 'upperalpha',
                      'lowerroman', 'upperroman'] # ORDERED!
    enum.sequencepats = {'arabic': '[0-9]+',
                         'loweralpha': '[a-z]',
                         'upperalpha': '[A-Z]',
                         'lowerroman': '[ivxlcdm]+',
                         'upperroman': '[IVXLCDM]+',}
    enum.converters = {'arabic': int,
                       'loweralpha':
                       lambda s, zero=(ord('a')-1): ord(s) - zero,
                       'upperalpha':
                       lambda s, zero=(ord('A')-1): ord(s) - zero,
                       'lowerroman':
                       lambda s: roman.fromRoman(s.upper()),
                       'upperroman': roman.fromRoman}

    enum.sequenceregexps = {}
    for sequence in enum.sequences:
        enum.sequenceregexps[sequence] = re.compile(
              enum.sequencepats[sequence] + '$')

    grid_table_top_pat = re.compile(r'\+-[-+]+-\+ *$')
    """Matches the top (& bottom) of a full table)."""

    simple_table_top_pat = re.compile('=+( +=+)+ *$')
    """Matches the top of a simple table."""

    simple_table_border_pat = re.compile('=+[ =]*$')
    """Matches the bottom & header bottom of a simple table."""

    pats = {}
    """Fragments of patterns used by transitions."""

    pats['nonalphanum7bit'] = '[!-/:-@[-`{-~]'
    pats['alpha'] = '[a-zA-Z]'
    pats['alphanum'] = '[a-zA-Z0-9]'
    pats['alphanumplus'] = '[a-zA-Z0-9_-]'
    pats['enum'] = ('(%(arabic)s|%(loweralpha)s|%(upperalpha)s|%(lowerroman)s'
                    '|%(upperroman)s)' % enum.sequencepats)
    pats['optname'] = '%(alphanum)s%(alphanumplus)s*' % pats
    # @@@ Loosen up the pattern?  Allow Unicode?
    pats['optarg'] = '%(alpha)s%(alphanumplus)s*' % pats
    pats['option'] = r'(--?|\+|/)%(optname)s([ =]%(optarg)s)?' % pats

    for format in enum.formats:
        pats[format] = '(?P<%s>%s%s%s)' % (
              format, re.escape(enum.formatinfo[format].prefix),
              pats['enum'], re.escape(enum.formatinfo[format].suffix))

    patterns = {
          'bullet': r'[-+*]( +|$)',
          'enumerator': r'(%(parens)s|%(rparen)s|%(period)s)( +|$)' % pats,
          'field_marker': r':[^: ]([^:]*[^: ])?:( +|$)',
          'option_marker': r'%(option)s(, %(option)s)*(  +| ?$)' % pats,
          'doctest': r'>>>( +|$)',
          'grid_table_top': grid_table_top_pat,
          'simple_table_top': simple_table_top_pat,
          'explicit_markup': r'\.\.( +|$)',
          'anonymous': r'__( +|$)',
          'line': r'(%(nonalphanum7bit)s)\1* *$' % pats,
          'text': r''}
    initial_transitions = (
          'bullet',
          'enumerator',
          'field_marker',
          'option_marker',
          'doctest',
          'grid_table_top',
          'simple_table_top',
          'explicit_markup',
          'anonymous',
          'line',
          'text')

    def indent(self, match, context, next_state):
        """Block quote."""
        indented, indent, line_offset, blank_finish = \
              self.state_machine.get_indented()
        blockquote = self.block_quote(indented, line_offset)
        self.parent += blockquote
        if not blank_finish:
            self.parent += self.unindent_warning('Block quote')
        return context, next_state, []

    def block_quote(self, indented, line_offset):
        blockquote = nodes.block_quote()
        self.nested_parse(indented, line_offset, blockquote)
        return blockquote

    def bullet(self, match, context, next_state):
        """Bullet list item."""
        bulletlist = nodes.bullet_list()
        self.parent += bulletlist
        bulletlist['bullet'] = match.string[0]
        i, blank_finish = self.list_item(match.end())
        bulletlist += i
        offset = self.state_machine.line_offset + 1   # next line
        newline_offset, blank_finish = self.nested_list_parse(
              self.state_machine.input_lines[offset:],
              input_offset=self.state_machine.abs_line_offset() + 1,
              node=bulletlist, initial_state='BulletList',
              blank_finish=blank_finish)
        self.goto_line(newline_offset)
        if not blank_finish:
            self.parent += self.unindent_warning('Bullet list')
        return [], next_state, []

    def list_item(self, indent):
        indented, line_offset, blank_finish = \
              self.state_machine.get_known_indented(indent)
        listitem = nodes.list_item('\n'.join(indented))
        if indented:
            self.nested_parse(indented, input_offset=line_offset,
                              node=listitem)
        return listitem, blank_finish

    def enumerator(self, match, context, next_state):
        """Enumerated List Item"""
        format, sequence, text, ordinal = self.parse_enumerator(match)
        if not self.is_enumerated_list_item(ordinal, sequence, format):
            raise statemachine.TransitionCorrection('text')
        if ordinal != 1:
            msg = self.reporter.info(
                'Enumerated list start value not ordinal-1: "%s" (ordinal %s)'
                % (text, ordinal), line=self.state_machine.abs_line_number())
            self.parent += msg
        enumlist = nodes.enumerated_list()
        self.parent += enumlist
        enumlist['enumtype'] = sequence
        if ordinal != 1:
            enumlist['start'] = ordinal
        enumlist['prefix'] = self.enum.formatinfo[format].prefix
        enumlist['suffix'] = self.enum.formatinfo[format].suffix
        listitem, blank_finish = self.list_item(match.end())
        enumlist += listitem
        offset = self.state_machine.line_offset + 1   # next line
        newline_offset, blank_finish = self.nested_list_parse(
              self.state_machine.input_lines[offset:],
              input_offset=self.state_machine.abs_line_offset() + 1,
              node=enumlist, initial_state='EnumeratedList',
              blank_finish=blank_finish,
              extra_settings={'lastordinal': ordinal, 'format': format})
        self.goto_line(newline_offset)
        if not blank_finish:
            self.parent += self.unindent_warning('Enumerated list')
        return [], next_state, []

    def parse_enumerator(self, match, expected_sequence=None):
        """
        Analyze an enumerator and return the results.

        :Return:
            - the enumerator format ('period', 'parens', or 'rparen'),
            - the sequence used ('arabic', 'loweralpha', 'upperroman', etc.),
            - the text of the enumerator, stripped of formatting, and
            - the ordinal value of the enumerator ('a' -> 1, 'ii' -> 2, etc.;
              ``None`` is returned for invalid enumerator text).

        The enumerator format has already been determined by the regular
        expression match. If `expected_sequence` is given, that sequence is
        tried first. If not, we check for Roman numeral 1. This way,
        single-character Roman numerals (which are also alphabetical) can be
        matched. If no sequence has been matched, all sequences are checked in
        order.
        """
        groupdict = match.groupdict()
        sequence = ''
        for format in self.enum.formats:
            if groupdict[format]:       # was this the format matched?
                break                   # yes; keep `format`
        else:                           # shouldn't happen
            raise ParserError('enumerator format not matched')
        text = groupdict[format][self.enum.formatinfo[format].start
                                 :self.enum.formatinfo[format].end]
        if expected_sequence:
            try:
                if self.enum.sequenceregexps[expected_sequence].match(text):
                    sequence = expected_sequence
            except KeyError:            # shouldn't happen
                raise ParserError('unknown enumerator sequence: %s'
                                  % sequence)
        elif text == 'i':
            sequence = 'lowerroman'
        elif text == 'I':
            sequence = 'upperroman'
        if not sequence:
            for sequence in self.enum.sequences:
                if self.enum.sequenceregexps[sequence].match(text):
                    break
            else:                       # shouldn't happen
                raise ParserError('enumerator sequence not matched')
        try:
            ordinal = self.enum.converters[sequence](text)
        except roman.InvalidRomanNumeralError:
            ordinal = None
        return format, sequence, text, ordinal

    def is_enumerated_list_item(self, ordinal, sequence, format):
        """
        Check validity based on the ordinal value and the second line.

        Return true iff the ordinal is valid and the second line is blank,
        indented, or starts with the next enumerator.
        """
        if ordinal is None:
            return None
        try:
            next_line = self.state_machine.next_line()
        except EOFError:              # end of input lines
            self.state_machine.previous_line()
            return 1
        else:
            self.state_machine.previous_line()
        if not next_line[:1].strip():   # blank or indented
            return 1
        next_enumerator = self.make_enumerator(ordinal + 1, sequence, format)
        try:
            if next_line.startswith(next_enumerator):
                return 1
        except TypeError:
            pass
        return None

    def make_enumerator(self, ordinal, sequence, format):
        """
        Construct and return an enumerated list item marker.

        Return ``None`` for invalid (out of range) ordinals.
        """
        if sequence == 'arabic':
            enumerator = str(ordinal)
        else:
            if sequence.endswith('alpha'):
                if ordinal > 26:
                    return None
                enumerator = chr(ordinal + ord('a') - 1)
            elif sequence.endswith('roman'):
                try:
                    enumerator = roman.toRoman(ordinal)
                except roman.RomanError:
                    return None
            else:                       # shouldn't happen
                raise ParserError('unknown enumerator sequence: "%s"'
                                  % sequence)
            if sequence.startswith('lower'):
                enumerator = enumerator.lower()
            elif sequence.startswith('upper'):
                enumerator = enumerator.upper()
            else:                       # shouldn't happen
                raise ParserError('unknown enumerator sequence: "%s"'
                                  % sequence)
        formatinfo = self.enum.formatinfo[format]
        return formatinfo.prefix + enumerator + formatinfo.suffix + ' '

    def field_marker(self, match, context, next_state):
        """Field list item."""
        fieldlist = nodes.field_list()
        self.parent += fieldlist
        field, blank_finish = self.field(match)
        fieldlist += field
        offset = self.state_machine.line_offset + 1   # next line
        newline_offset, blank_finish = self.nested_list_parse(
              self.state_machine.input_lines[offset:],
              input_offset=self.state_machine.abs_line_offset() + 1,
              node=fieldlist, initial_state='FieldList',
              blank_finish=blank_finish)
        self.goto_line(newline_offset)
        if not blank_finish:
            self.parent += self.unindent_warning('Field list')
        return [], next_state, []

    def field(self, match):
        name = self.parse_field_marker(match)
        lineno = self.state_machine.abs_line_number()
        indented, indent, line_offset, blank_finish = \
              self.state_machine.get_first_known_indented(match.end())
        fieldnode = nodes.field()
        fieldnode.line = lineno
        fieldnode += nodes.field_name(name, name)
        fieldbody = nodes.field_body('\n'.join(indented))
        fieldnode += fieldbody
        if indented:
            self.parse_field_body(indented, line_offset, fieldbody)
        return fieldnode, blank_finish

    def parse_field_marker(self, match):
        """Extract & return field name from a field marker match."""
        field = match.string[1:]        # strip off leading ':'
        field = field[:field.find(':')] # strip off trailing ':' etc.
        return field

    def parse_field_body(self, indented, offset, node):
        self.nested_parse(indented, input_offset=offset, node=node)

    def option_marker(self, match, context, next_state):
        """Option list item."""
        optionlist = nodes.option_list()
        try:
            listitem, blank_finish = self.option_list_item(match)
        except MarkupError, (message, lineno):
            # This shouldn't happen; pattern won't match.
            msg = self.reporter.error(
                'Invalid option list marker: %s' % message, line=lineno)
            self.parent += msg
            indented, indent, line_offset, blank_finish = \
                  self.state_machine.get_first_known_indented(match.end())
            blockquote = self.block_quote(indented, line_offset)
            self.parent += blockquote
            if not blank_finish:
                self.parent += self.unindent_warning('Option list')
            return [], next_state, []
        self.parent += optionlist
        optionlist += listitem
        offset = self.state_machine.line_offset + 1   # next line
        newline_offset, blank_finish = self.nested_list_parse(
              self.state_machine.input_lines[offset:],
              input_offset=self.state_machine.abs_line_offset() + 1,
              node=optionlist, initial_state='OptionList',
              blank_finish=blank_finish)
        self.goto_line(newline_offset)
        if not blank_finish:
            self.parent += self.unindent_warning('Option list')
        return [], next_state, []

    def option_list_item(self, match):
        offset = self.state_machine.abs_line_offset()
        options = self.parse_option_marker(match)
        indented, indent, line_offset, blank_finish = \
              self.state_machine.get_first_known_indented(match.end())
        if not indented:                # not an option list item
            self.goto_line(offset)
            raise statemachine.TransitionCorrection('text')
        option_group = nodes.option_group('', *options)
        description = nodes.description('\n'.join(indented))
        option_list_item = nodes.option_list_item('', option_group,
                                                  description)
        if indented:
            self.nested_parse(indented, input_offset=line_offset,
                              node=description)
        return option_list_item, blank_finish

    def parse_option_marker(self, match):
        """
        Return a list of `node.option` and `node.option_argument` objects,
        parsed from an option marker match.

        :Exception: `MarkupError` for invalid option markers.
        """
        optlist = []
        optionstrings = match.group().rstrip().split(', ')
        for optionstring in optionstrings:
            tokens = optionstring.split()
            delimiter = ' '
            firstopt = tokens[0].split('=')
            if len(firstopt) > 1:
                tokens[:1] = firstopt
                delimiter = '='
            if 0 < len(tokens) <= 2:
                option = nodes.option(optionstring)
                option += nodes.option_string(tokens[0], tokens[0])
                if len(tokens) > 1:
                    option += nodes.option_argument(tokens[1], tokens[1],
                                                    delimiter=delimiter)
                optlist.append(option)
            else:
                raise MarkupError(
                    'wrong numer of option tokens (=%s), should be 1 or 2: '
                    '"%s"' % (len(tokens), optionstring),
                    self.state_machine.abs_line_number() + 1)
        return optlist

    def doctest(self, match, context, next_state):
        data = '\n'.join(self.state_machine.get_text_block())
        self.parent += nodes.doctest_block(data, data)
        return [], next_state, []

    def grid_table_top(self, match, context, next_state):
        """Top border of a full table."""
        return self.table_top(match, context, next_state,
                              self.isolate_grid_table,
                              tableparser.GridTableParser)

    def simple_table_top(self, match, context, next_state):
        """Top border of a simple table."""
        return self.table_top(match, context, next_state,
                              self.isolate_simple_table,
                              tableparser.SimpleTableParser)

    def table_top(self, match, context, next_state,
                  isolate_function, parser_class):
        """Top border of a generic table."""
        nodelist, blank_finish = self.table(isolate_function, parser_class)
        self.parent += nodelist
        if not blank_finish:
            msg = self.reporter.warning(
                'Blank line required after table.',
                line=self.state_machine.abs_line_number() + 1)
            self.parent += msg
        return [], next_state, []

    def table(self, isolate_function, parser_class):
        """Parse a table."""
        block, messages, blank_finish = isolate_function()
        if block:
            try:
                parser = parser_class()
                tabledata = parser.parse(block)
                tableline = (self.state_machine.abs_line_number() - len(block)
                             + 1)
                table = self.build_table(tabledata, tableline)
                nodelist = [table] + messages
            except tableparser.TableMarkupError, detail:
                nodelist = self.malformed_table(block, str(detail)) + messages
        else:
            nodelist = messages
        return nodelist, blank_finish

    def isolate_grid_table(self):
        messages = []
        blank_finish = 1
        try:
            block = self.state_machine.get_text_block(flush_left=1)
        except statemachine.UnexpectedIndentationError, instance:
            block, source, lineno = instance.args
            messages.append(self.reporter.error('Unexpected indentation.',
                                                source=source, line=lineno))
            blank_finish = 0
        block.disconnect()
        width = len(block[0].strip())
        for i in range(len(block)):
            block[i] = block[i].strip()
            if block[i][0] not in '+|': # check left edge
                blank_finish = 0
                self.state_machine.previous_line(len(block) - i)
                del block[i:]
                break
        if not self.grid_table_top_pat.match(block[-1]): # find bottom
            blank_finish = 0
            # from second-last to third line of table:
            for i in range(len(block) - 2, 1, -1):
                if self.grid_table_top_pat.match(block[i]):
                    self.state_machine.previous_line(len(block) - i + 1)
                    del block[i+1:]
                    break
            else:
                messages.extend(self.malformed_table(block))
                return [], messages, blank_finish
        for i in range(len(block)):     # check right edge
            if len(block[i]) != width or block[i][-1] not in '+|':
                messages.extend(self.malformed_table(block))
                return [], messages, blank_finish
        return block, messages, blank_finish

    def isolate_simple_table(self):
        start = self.state_machine.line_offset
        lines = self.state_machine.input_lines
        limit = len(lines) - 1
        toplen = len(lines[start].strip())
        pattern_match = self.simple_table_border_pat.match
        found = 0
        found_at = None
        i = start + 1
        while i <= limit:
            line = lines[i]
            match = pattern_match(line)
            if match:
                if len(line.strip()) != toplen:
                    self.state_machine.next_line(i - start)
                    messages = self.malformed_table(
                        lines[start:i+1], 'Bottom/header table border does '
                        'not match top border.')
                    return [], messages, i == limit or not lines[i+1].strip()
                found += 1
                found_at = i
                if found == 2 or i == limit or not lines[i+1].strip():
                    end = i
                    break
            i += 1
        else:                           # reached end of input_lines
            if found:
                extra = ' or no blank line after table bottom'
                self.state_machine.next_line(found_at - start)
                block = lines[start:found_at+1]
            else:
                extra = ''
                self.state_machine.next_line(i - start - 1)
                block = lines[start:]
            messages = self.malformed_table(
                block, 'No bottom table border found%s.' % extra)
            return [], messages, not extra
        self.state_machine.next_line(end - start)
        block = lines[start:end+1]
        return block, [], end == limit or not lines[end+1].strip()

    def malformed_table(self, block, detail=''):
        data = '\n'.join(block)
        message = 'Malformed table.'
        lineno = self.state_machine.abs_line_number() - len(block) + 1
        if detail:
            message += '\n' + detail
        error = self.reporter.error(message, nodes.literal_block(data, data),
                                    line=lineno)
        return [error]

    def build_table(self, tabledata, tableline):
        colspecs, headrows, bodyrows = tabledata
        table = nodes.table()
        tgroup = nodes.tgroup(cols=len(colspecs))
        table += tgroup
        for colspec in colspecs:
            tgroup += nodes.colspec(colwidth=colspec)
        if headrows:
            thead = nodes.thead()
            tgroup += thead
            for row in headrows:
                thead += self.build_table_row(row, tableline)
        tbody = nodes.tbody()
        tgroup += tbody
        for row in bodyrows:
            tbody += self.build_table_row(row, tableline)
        return table

    def build_table_row(self, rowdata, tableline):
        row = nodes.row()
        for cell in rowdata:
            if cell is None:
                continue
            morerows, morecols, offset, cellblock = cell
            attributes = {}
            if morerows:
                attributes['morerows'] = morerows
            if morecols:
                attributes['morecols'] = morecols
            entry = nodes.entry(**attributes)
            row += entry
            if ''.join(cellblock):
                self.nested_parse(cellblock, input_offset=tableline+offset,
                                  node=entry)
        return row


    explicit = Struct()
    """Patterns and constants used for explicit markup recognition."""

    explicit.patterns = Struct(
          target=re.compile(r"""
                            (
                              _               # anonymous target
                            |               # *OR*
                              (?P<quote>`?)   # optional open quote
                              (?![ `])        # first char. not space or
                                              # backquote
                              (?P<name>       # reference name
                                .+?
                              )
                              %(non_whitespace_escape_before)s
                              (?P=quote)      # close quote if open quote used
                            )
                            %(non_whitespace_escape_before)s
                            :               # end of reference name
                            ([ ]+|$)        # followed by whitespace
                            """ % vars(Inliner), re.VERBOSE),
          reference=re.compile(r"""
                               (
                                 (?P<simple>%(simplename)s)_
                               |                  # *OR*
                                 `                  # open backquote
                                 (?![ ])            # not space
                                 (?P<phrase>.+?)    # hyperlink phrase
                                 %(non_whitespace_escape_before)s
                                 `_                 # close backquote,
                                                    # reference mark
                               )
                               $                  # end of string
                               """ % vars(Inliner), re.VERBOSE | re.UNICODE),
          substitution=re.compile(r"""
                                  (
                                    (?![ ])          # first char. not space
                                    (?P<name>.+?)    # substitution text
                                    %(non_whitespace_escape_before)s
                                    \|               # close delimiter
                                  )
                                  ([ ]+|$)           # followed by whitespace
                                  """ % vars(Inliner), re.VERBOSE),)

    def footnote(self, match):
        lineno = self.state_machine.abs_line_number()
        indented, indent, offset, blank_finish = \
              self.state_machine.get_first_known_indented(match.end())
        label = match.group(1)
        name = normalize_name(label)
        footnote = nodes.footnote('\n'.join(indented))
        footnote.line = lineno
        if name[0] == '#':              # auto-numbered
            name = name[1:]             # autonumber label
            footnote['auto'] = 1
            if name:
                footnote['name'] = name
            self.document.note_autofootnote(footnote)
        elif name == '*':               # auto-symbol
            name = ''
            footnote['auto'] = '*'
            self.document.note_symbol_footnote(footnote)
        else:                           # manually numbered
            footnote += nodes.label('', label)
            footnote['name'] = name
            self.document.note_footnote(footnote)
        if name:
            self.document.note_explicit_target(footnote, footnote)
        else:
            self.document.set_id(footnote, footnote)
        if indented:
            self.nested_parse(indented, input_offset=offset, node=footnote)
        return [footnote], blank_finish

    def citation(self, match):
        lineno = self.state_machine.abs_line_number()
        indented, indent, offset, blank_finish = \
              self.state_machine.get_first_known_indented(match.end())
        label = match.group(1)
        name = normalize_name(label)
        citation = nodes.citation('\n'.join(indented))
        citation.line = lineno
        citation += nodes.label('', label)
        citation['name'] = name
        self.document.note_citation(citation)
        self.document.note_explicit_target(citation, citation)
        if indented:
            self.nested_parse(indented, input_offset=offset, node=citation)
        return [citation], blank_finish

    def hyperlink_target(self, match):
        pattern = self.explicit.patterns.target
        lineno = self.state_machine.abs_line_number()
        block, indent, offset, blank_finish = \
              self.state_machine.get_first_known_indented(
              match.end(), until_blank=1, strip_indent=0)
        blocktext = match.string[:match.end()] + '\n'.join(block)
        block = [escape2null(line) for line in block]
        escaped = block[0]
        blockindex = 0
        while 1:
            targetmatch = pattern.match(escaped)
            if targetmatch:
                break
            blockindex += 1
            try:
                escaped += block[blockindex]
            except IndexError:
                raise MarkupError('malformed hyperlink target.', lineno)
        del block[:blockindex]
        block[0] = (block[0] + ' ')[targetmatch.end()-len(escaped)-1:].strip()
        if block and block[-1].strip()[-1:] == '_': # possible indirect target
            reference = ' '.join([line.strip() for line in block])
            refname = self.is_reference(reference)
            if refname:
                target = nodes.target(blocktext, '', refname=refname)
                target.line = lineno
                self.add_target(targetmatch.group('name'), '', target)
                self.document.note_indirect_target(target)
                return [target], blank_finish
        nodelist = []
        reference = ''.join([line.strip() for line in block])
        if reference.find(' ') != -1:
            warning = self.reporter.warning(
                  'Hyperlink target contains whitespace. Perhaps a footnote '
                  'was intended?',
                  nodes.literal_block(blocktext, blocktext), line=lineno)
            nodelist.append(warning)
        else:
            unescaped = unescape(reference)
            target = nodes.target(blocktext, '')
            target.line = lineno
            self.add_target(targetmatch.group('name'), unescaped, target)
            nodelist.append(target)
        return nodelist, blank_finish

    def is_reference(self, reference):
        match = self.explicit.patterns.reference.match(
            normalize_name(reference))
        if not match:
            return None
        return unescape(match.group('simple') or match.group('phrase'))

    def add_target(self, targetname, refuri, target):
        if targetname:
            name = normalize_name(unescape(targetname))
            target['name'] = name
            if refuri:
                uri = self.inliner.adjust_uri(refuri)
                if uri:
                    target['refuri'] = uri
                    self.document.note_external_target(target)
                else:
                    raise ApplicationError('problem with URI: %r' % refuri)
            else:
                self.document.note_internal_target(target)
            self.document.note_explicit_target(target, self.parent)
        else:                       # anonymous target
            if refuri:
                target['refuri'] = refuri
            target['anonymous'] = 1
            self.document.note_anonymous_target(target)

    def substitution_def(self, match):
        pattern = self.explicit.patterns.substitution
        lineno = self.state_machine.abs_line_number()
        block, indent, offset, blank_finish = \
              self.state_machine.get_first_known_indented(match.end(),
                                                          strip_indent=0)
        blocktext = (match.string[:match.end()] + '\n'.join(block))
        block.disconnect()
        for i in range(len(block)):
            block[i] = escape2null(block[i])
        escaped = block[0].rstrip()
        blockindex = 0
        while 1:
            subdefmatch = pattern.match(escaped)
            if subdefmatch:
                break
            blockindex += 1
            try:
                escaped = escaped + ' ' + block[blockindex].strip()
            except IndexError:
                raise MarkupError('malformed substitution definition.',
                                  lineno)
        del block[:blockindex]          # strip out the substitution marker
        block[0] = (block[0] + ' ')[subdefmatch.end()-len(escaped)-1:].strip()
        if not block[0]:
            del block[0]
            offset += 1
        while block and not block[-1].strip():
            block.pop()
        subname = subdefmatch.group('name')
        name = normalize_name(subname)
        substitutionnode = nodes.substitution_definition(
              blocktext, name=name, alt=subname)
        substitutionnode.line = lineno
        if block:
            block[0] = block[0].strip()
            new_abs_offset, blank_finish = self.nested_list_parse(
                  block, input_offset=offset, node=substitutionnode,
                  initial_state='SubstitutionDef', blank_finish=blank_finish)
            i = 0
            for node in substitutionnode[:]:
                if not (isinstance(node, nodes.Inline) or
                        isinstance(node, nodes.Text)):
                    self.parent += substitutionnode[i]
                    del substitutionnode[i]
                else:
                    i += 1
            if len(substitutionnode) == 0:
                msg = self.reporter.warning(
                      'Substitution definition "%s" empty or invalid.'
                      % subname,
                      nodes.literal_block(blocktext, blocktext), line=lineno)
                return [msg], blank_finish
            else:
                del substitutionnode['alt']
                self.document.note_substitution_def(
                      substitutionnode, self.parent)
                return [substitutionnode], blank_finish
        else:
            msg = self.reporter.warning(
                  'Substitution definition "%s" missing contents.' % subname,
                  nodes.literal_block(blocktext, blocktext), line=lineno)
            return [msg], blank_finish

    def directive(self, match, **option_presets):
        type_name = match.group(1)
        directive_function, messages = directives.directive(
            type_name, self.memo.language, self.document)
        self.parent += messages
        if directive_function:
            return self.parse_directive(
                directive_function, match, type_name, option_presets)
        else:
            return self.unknown_directive(type_name)

    def parse_directive(self, directive_fn, match, type_name, option_presets):
        """
        Parse a directive then run its directive function.

        Parameters:

        - `directive_fn`: The function implementing the directive.  Uses
          function attributes ``arguments``, ``options``, and/or ``content``
          if present.

        - `match`: A regular expression match object which matched the first
          line of the directive.

        - `type_name`: The directive name, as used in the source text.

        - `option_presets`: A dictionary of preset options, defaults for the
          directive options.  Currently, only an "alt" option is passed by
          substitution definitions (value: the substitution name), which may
          be used by an embedded image directive.

        Returns a 2-tuple: list of nodes, and a "blank finish" boolean.
        """
        arguments = []
        options = {}
        argument_spec = getattr(directive_fn, 'arguments', None)
        if argument_spec and argument_spec[:2] == (0, 0):
            argument_spec = None
        option_spec = getattr(directive_fn, 'options', None)
        content_spec = getattr(directive_fn, 'content', None)
        lineno = self.state_machine.abs_line_number()
        initial_line_offset = self.state_machine.line_offset
        indented, indent, line_offset, blank_finish \
                  = self.state_machine.get_first_known_indented(match.end(),
                                                                strip_top=0)
        block_text = '\n'.join(self.state_machine.input_lines[
            initial_line_offset : self.state_machine.line_offset + 1])
        if indented and not indented[0].strip():
            indented.trim_start()
            line_offset += 1
        while indented and not indented[-1].strip():
            indented.trim_end()
        if indented and (argument_spec or option_spec):
            for i in range(len(indented)):
                if not indented[i].strip():
                    break
            else:
                i += 1
            arg_block = indented[:i]
            content = indented[i+1:]
            content_offset = line_offset + i + 1
        else:
            content = indented
            content_offset = line_offset
            arg_block = []
        while content and not content[0].strip():
            content.trim_start()
            content_offset += 1
        try:
            if option_spec:
                options, arg_block = self.parse_directive_options(
                    option_presets, option_spec, arg_block)
            if argument_spec:
                arguments = self.parse_directive_arguments(argument_spec,
                                                           arg_block)
            if content and not content_spec:
                raise MarkupError('no content permitted.')
        except MarkupError, detail:
            error = self.reporter.error(
                'Error in "%s" directive:\n%s.' % (type_name, detail),
                nodes.literal_block(block_text, block_text), line=lineno)
            return [error], blank_finish
        result = directive_fn(
            type_name, arguments, options, content, lineno, content_offset,
            block_text, self, self.state_machine)
        return result, blank_finish or self.state_machine.is_next_line_blank()

    def parse_directive_options(self, option_presets, option_spec, arg_block):
        options = option_presets.copy()
        for i in range(len(arg_block)):
            if arg_block[i][:1] == ':':
                opt_block = arg_block[i:]
                arg_block = arg_block[:i]
                break
        else:
            opt_block = []
        if opt_block:
            success, data = self.parse_extension_options(option_spec,
                                                         opt_block)
            if success:                 # data is a dict of options
                options.update(data)
            else:                       # data is an error string
                raise MarkupError(data)
        return options, arg_block

    def parse_directive_arguments(self, argument_spec, arg_block):
        required, optional, last_whitespace = argument_spec
        arg_text = '\n'.join(arg_block)
        arguments = arg_text.split()
        if len(arguments) < required:
            raise MarkupError('%s argument(s) required, %s supplied'
                              % (required, len(arguments)))
        elif len(arguments) > required + optional:
            if last_whitespace:
                arguments = arg_text.split(None, required + optional - 1)
            else:
                raise MarkupError(
                    'maximum %s argument(s) allowed, %s supplied'
                    % (required + optional, len(arguments)))
        return arguments

    def parse_extension_options(self, option_spec, datalines):
        """
        Parse `datalines` for a field list containing extension options
        matching `option_spec`.

        :Parameters:
            - `option_spec`: a mapping of option name to conversion
              function, which should raise an exception on bad input.
            - `datalines`: a list of input strings.

        :Return:
            - Success value, 1 or 0.
            - An option dictionary on success, an error string on failure.
        """
        node = nodes.field_list()
        newline_offset, blank_finish = self.nested_list_parse(
              datalines, 0, node, initial_state='ExtensionOptions',
              blank_finish=1)
        if newline_offset != len(datalines): # incomplete parse of block
            return 0, 'invalid option block'
        try:
            options = utils.extract_extension_options(node, option_spec)
        except KeyError, detail:
            return 0, ('unknown option: "%s"' % detail.args[0])
        except (ValueError, TypeError), detail:
            return 0, ('invalid option value: %s' % detail)
        except utils.ExtensionOptionError, detail:
            return 0, ('invalid option data: %s' % detail)
        if blank_finish:
            return 1, options
        else:
            return 0, 'option data incompletely parsed'

    def unknown_directive(self, type_name):
        lineno = self.state_machine.abs_line_number()
        indented, indent, offset, blank_finish = \
              self.state_machine.get_first_known_indented(0, strip_indent=0)
        text = '\n'.join(indented)
        error = self.reporter.error(
              'Unknown directive type "%s".' % type_name,
              nodes.literal_block(text, text), line=lineno)
        return [error], blank_finish

    def comment(self, match):
        if not match.string[match.end():].strip() \
              and self.state_machine.is_next_line_blank(): # an empty comment?
            return [nodes.comment()], 1 # "A tiny but practical wart."
        indented, indent, offset, blank_finish = \
              self.state_machine.get_first_known_indented(match.end())
        while indented and not indented[-1].strip():
            indented.trim_end()
        text = '\n'.join(indented)
        return [nodes.comment(text, text)], blank_finish

    explicit.constructs = [
          (footnote,
           re.compile(r"""
                      \.\.[ ]+          # explicit markup start
                      \[
                      (                 # footnote label:
                          [0-9]+          # manually numbered footnote
                        |               # *OR*
                          \#              # anonymous auto-numbered footnote
                        |               # *OR*
                          \#%s            # auto-number ed?) footnote label
                        |               # *OR*
                          \*              # auto-symbol footnote
                      )
                      \]
                      ([ ]+|$)          # whitespace or end of line
                      """ % Inliner.simplename, re.VERBOSE | re.UNICODE)),
          (citation,
           re.compile(r"""
                      \.\.[ ]+          # explicit markup start
                      \[(%s)\]          # citation label
                      ([ ]+|$)          # whitespace or end of line
                      """ % Inliner.simplename, re.VERBOSE | re.UNICODE)),
          (hyperlink_target,
           re.compile(r"""
                      \.\.[ ]+          # explicit markup start
                      _                 # target indicator
                      (?![ ])           # first char. not space
                      """, re.VERBOSE)),
          (substitution_def,
           re.compile(r"""
                      \.\.[ ]+          # explicit markup start
                      \|                # substitution indicator
                      (?![ ])           # first char. not space
                      """, re.VERBOSE)),
          (directive,
           re.compile(r"""
                      \.\.[ ]+          # explicit markup start
                      (%s)              # directive name
                      ::                # directive delimiter
                      ([ ]+|$)          # whitespace or end of line
                      """ % Inliner.simplename, re.VERBOSE | re.UNICODE))]

    def explicit_markup(self, match, context, next_state):
        """Footnotes, hyperlink targets, directives, comments."""
        nodelist, blank_finish = self.explicit_construct(match)
        self.parent += nodelist
        self.explicit_list(blank_finish)
        return [], next_state, []

    def explicit_construct(self, match):
        """Determine which explicit construct this is, parse & return it."""
        errors = []
        for method, pattern in self.explicit.constructs:
            expmatch = pattern.match(match.string)
            if expmatch:
                try:
                    return method(self, expmatch)
                except MarkupError, (message, lineno): # never reached?
                    errors.append(self.reporter.warning(message, line=lineno))
                    break
        nodelist, blank_finish = self.comment(match)
        return nodelist + errors, blank_finish

    def explicit_list(self, blank_finish):
        """
        Create a nested state machine for a series of explicit markup
        constructs (including anonymous hyperlink targets).
        """
        offset = self.state_machine.line_offset + 1   # next line
        newline_offset, blank_finish = self.nested_list_parse(
              self.state_machine.input_lines[offset:],
              input_offset=self.state_machine.abs_line_offset() + 1,
              node=self.parent, initial_state='Explicit',
              blank_finish=blank_finish)
        self.goto_line(newline_offset)
        if not blank_finish:
            self.parent += self.unindent_warning('Explicit markup')

    def anonymous(self, match, context, next_state):
        """Anonymous hyperlink targets."""
        nodelist, blank_finish = self.anonymous_target(match)
        self.parent += nodelist
        self.explicit_list(blank_finish)
        return [], next_state, []

    def anonymous_target(self, match):
        block, indent, offset, blank_finish \
              = self.state_machine.get_first_known_indented(match.end(),
                                                            until_blank=1)
        blocktext = match.string[:match.end()] + '\n'.join(block)
        if block and block[-1].strip()[-1:] == '_': # possible indirect target
            reference = escape2null(' '.join([line.strip()
                                              for line in block]))
            refname = self.is_reference(reference)
            if refname:
                target = nodes.target(blocktext, '', refname=refname,
                                      anonymous=1)
                self.document.note_anonymous_target(target)
                self.document.note_indirect_target(target)
                return [target], blank_finish
        nodelist = []
        reference = escape2null(''.join([line.strip() for line in block]))
        if reference.find(' ') != -1:
            lineno = self.state_machine.abs_line_number() - len(block) + 1
            warning = self.reporter.warning(
                  'Anonymous hyperlink target contains whitespace. Perhaps a '
                  'footnote was intended?',
                  nodes.literal_block(blocktext, blocktext),
                  line=lineno)
            nodelist.append(warning)
        else:
            target = nodes.target(blocktext, '', anonymous=1)
            if reference:
                unescaped = unescape(reference)
                target['refuri'] = unescaped
            self.document.note_anonymous_target(target)
            nodelist.append(target)
        return nodelist, blank_finish

    def line(self, match, context, next_state):
        """Section title overline or transition marker."""
        if self.state_machine.match_titles:
            return [match.string], 'Line', []
        elif match.string.strip() == '::':
            raise statemachine.TransitionCorrection('text')
        elif len(match.string.strip()) < 4:
            msg = self.reporter.info(
                'Unexpected possible title overline or transition.\n'
                "Treating it as ordinary text because it's so short.",
                line=self.state_machine.abs_line_number())
            self.parent += msg
            raise statemachine.TransitionCorrection('text')
        else:
            blocktext = self.state_machine.line
            msg = self.reporter.severe(
                  'Unexpected section title or transition.',
                  nodes.literal_block(blocktext, blocktext),
                  line=self.state_machine.abs_line_number())
            self.parent += msg
            return [], next_state, []

    def text(self, match, context, next_state):
        """Titles, definition lists, paragraphs."""
        return [match.string], 'Text', []


class RFC2822Body(Body):

    """
    RFC2822 headers are only valid as the first constructs in documents.  As
    soon as anything else appears, the `Body` state should take over.
    """

    patterns = Body.patterns.copy()     # can't modify the original
    patterns['rfc2822'] = r'[!-9;-~]+:( +|$)'
    initial_transitions = [(name, 'Body')
                           for name in Body.initial_transitions]
    initial_transitions.insert(-1, ('rfc2822', 'Body')) # just before 'text'

    def rfc2822(self, match, context, next_state):
        """RFC2822-style field list item."""
        fieldlist = nodes.field_list(CLASS='rfc2822')
        self.parent += fieldlist
        field, blank_finish = self.rfc2822_field(match)
        fieldlist += field
        offset = self.state_machine.line_offset + 1   # next line
        newline_offset, blank_finish = self.nested_list_parse(
              self.state_machine.input_lines[offset:],
              input_offset=self.state_machine.abs_line_offset() + 1,
              node=fieldlist, initial_state='RFC2822List',
              blank_finish=blank_finish)
        self.goto_line(newline_offset)
        if not blank_finish:
            self.parent += self.unindent_warning(
                  'RFC2822-style field list')
        return [], next_state, []

    def rfc2822_field(self, match):
        name = match.string[:match.string.find(':')]
        indented, indent, line_offset, blank_finish = \
              self.state_machine.get_first_known_indented(match.end(),
                                                          until_blank=1)
        fieldnode = nodes.field()
        fieldnode += nodes.field_name(name, name)
        fieldbody = nodes.field_body('\n'.join(indented))
        fieldnode += fieldbody
        if indented:
            self.nested_parse(indented, input_offset=line_offset,
                              node=fieldbody)
        return fieldnode, blank_finish


class SpecializedBody(Body):

    """
    Superclass for second and subsequent compound element members.  Compound
    elements are lists and list-like constructs.

    All transition methods are disabled (redefined as `invalid_input`).
    Override individual methods in subclasses to re-enable.

    For example, once an initial bullet list item, say, is recognized, the
    `BulletList` subclass takes over, with a "bullet_list" node as its
    container.  Upon encountering the initial bullet list item, `Body.bullet`
    calls its ``self.nested_list_parse`` (`RSTState.nested_list_parse`), which
    starts up a nested parsing session with `BulletList` as the initial state.
    Only the ``bullet`` transition method is enabled in `BulletList`; as long
    as only bullet list items are encountered, they are parsed and inserted
    into the container.  The first construct which is *not* a bullet list item
    triggers the `invalid_input` method, which ends the nested parse and
    closes the container.  `BulletList` needs to recognize input that is
    invalid in the context of a bullet list, which means everything *other
    than* bullet list items, so it inherits the transition list created in
    `Body`.
    """

    def invalid_input(self, match=None, context=None, next_state=None):
        """Not a compound element member. Abort this state machine."""
        self.state_machine.previous_line() # back up so parent SM can reassess
        raise EOFError

    indent = invalid_input
    bullet = invalid_input
    enumerator = invalid_input
    field_marker = invalid_input
    option_marker = invalid_input
    doctest = invalid_input
    grid_table_top = invalid_input
    simple_table_top = invalid_input
    explicit_markup = invalid_input
    anonymous = invalid_input
    line = invalid_input
    text = invalid_input


class BulletList(SpecializedBody):

    """Second and subsequent bullet_list list_items."""

    def bullet(self, match, context, next_state):
        """Bullet list item."""
        if match.string[0] != self.parent['bullet']:
            # different bullet: new list
            self.invalid_input()
        listitem, blank_finish = self.list_item(match.end())
        self.parent += listitem
        self.blank_finish = blank_finish
        return [], next_state, []


class DefinitionList(SpecializedBody):

    """Second and subsequent definition_list_items."""

    def text(self, match, context, next_state):
        """Definition lists."""
        return [match.string], 'Definition', []


class EnumeratedList(SpecializedBody):

    """Second and subsequent enumerated_list list_items."""

    def enumerator(self, match, context, next_state):
        """Enumerated list item."""
        format, sequence, text, ordinal = self.parse_enumerator(
              match, self.parent['enumtype'])
        if (sequence != self.parent['enumtype'] or
            format != self.format or
            ordinal != (self.lastordinal + 1) or
            not self.is_enumerated_list_item(ordinal, sequence, format)):
            # different enumeration: new list
            self.invalid_input()
        listitem, blank_finish = self.list_item(match.end())
        self.parent += listitem
        self.blank_finish = blank_finish
        self.lastordinal = ordinal
        return [], next_state, []


class FieldList(SpecializedBody):

    """Second and subsequent field_list fields."""

    def field_marker(self, match, context, next_state):
        """Field list field."""
        field, blank_finish = self.field(match)
        self.parent += field
        self.blank_finish = blank_finish
        return [], next_state, []


class OptionList(SpecializedBody):

    """Second and subsequent option_list option_list_items."""

    def option_marker(self, match, context, next_state):
        """Option list item."""
        try:
            option_list_item, blank_finish = self.option_list_item(match)
        except MarkupError, (message, lineno):
            self.invalid_input()
        self.parent += option_list_item
        self.blank_finish = blank_finish
        return [], next_state, []


class RFC2822List(SpecializedBody, RFC2822Body):

    """Second and subsequent RFC2822-style field_list fields."""

    patterns = RFC2822Body.patterns
    initial_transitions = RFC2822Body.initial_transitions

    def rfc2822(self, match, context, next_state):
        """RFC2822-style field list item."""
        field, blank_finish = self.rfc2822_field(match)
        self.parent += field
        self.blank_finish = blank_finish
        return [], 'RFC2822List', []

    blank = SpecializedBody.invalid_input


class ExtensionOptions(FieldList):

    """
    Parse field_list fields for extension options.

    No nested parsing is done (including inline markup parsing).
    """

    def parse_field_body(self, indented, offset, node):
        """Override `Body.parse_field_body` for simpler parsing."""
        lines = []
        for line in list(indented) + ['']:
            if line.strip():
                lines.append(line)
            elif lines:
                text = '\n'.join(lines)
                node += nodes.paragraph(text, text)
                lines = []


class Explicit(SpecializedBody):

    """Second and subsequent explicit markup construct."""

    def explicit_markup(self, match, context, next_state):
        """Footnotes, hyperlink targets, directives, comments."""
        nodelist, blank_finish = self.explicit_construct(match)
        self.parent += nodelist
        self.blank_finish = blank_finish
        return [], next_state, []

    def anonymous(self, match, context, next_state):
        """Anonymous hyperlink targets."""
        nodelist, blank_finish = self.anonymous_target(match)
        self.parent += nodelist
        self.blank_finish = blank_finish
        return [], next_state, []

    blank = SpecializedBody.invalid_input


class SubstitutionDef(Body):

    """
    Parser for the contents of a substitution_definition element.
    """

    patterns = {
          'embedded_directive': re.compile(r'(%s)::( +|$)'
                                           % Inliner.simplename, re.UNICODE),
          'text': r''}
    initial_transitions = ['embedded_directive', 'text']

    def embedded_directive(self, match, context, next_state):
        if self.parent.has_key('alt'):
            option_presets = {'alt': self.parent['alt']}
        else:
            option_presets = {}
        nodelist, blank_finish = self.directive(match, **option_presets)
        self.parent += nodelist
        if not self.state_machine.at_eof():
            self.blank_finish = blank_finish
        raise EOFError

    def text(self, match, context, next_state):
        if not self.state_machine.at_eof():
            self.blank_finish = self.state_machine.is_next_line_blank()
        raise EOFError


class Text(RSTState):

    """
    Classifier of second line of a text block.

    Could be a paragraph, a definition list item, or a title.
    """

    patterns = {'underline': Body.patterns['line'],
                'text': r''}
    initial_transitions = [('underline', 'Body'), ('text', 'Body')]

    def blank(self, match, context, next_state):
        """End of paragraph."""
        paragraph, literalnext = self.paragraph(
              context, self.state_machine.abs_line_number() - 1)
        self.parent += paragraph
        if literalnext:
            self.parent += self.literal_block()
        return [], 'Body', []

    def eof(self, context):
        if context:
            self.blank(None, context, None)
        return []

    def indent(self, match, context, next_state):
        """Definition list item."""
        definitionlist = nodes.definition_list()
        definitionlistitem, blank_finish = self.definition_list_item(context)
        definitionlist += definitionlistitem
        self.parent += definitionlist
        offset = self.state_machine.line_offset + 1   # next line
        newline_offset, blank_finish = self.nested_list_parse(
              self.state_machine.input_lines[offset:],
              input_offset=self.state_machine.abs_line_offset() + 1,
              node=definitionlist, initial_state='DefinitionList',
              blank_finish=blank_finish, blank_finish_state='Definition')
        self.goto_line(newline_offset)
        if not blank_finish:
            self.parent += self.unindent_warning('Definition list')
        return [], 'Body', []

    def underline(self, match, context, next_state):
        """Section title."""
        lineno = self.state_machine.abs_line_number()
        title = context[0].rstrip()
        underline = match.string.rstrip()
        source = title + '\n' + underline
        messages = []
        if len(title) > len(underline):
            if len(underline) < 4:
                if self.state_machine.match_titles:
                    msg = self.reporter.info(
                        'Possible title underline, too short for the title.\n'
                        "Treating it as ordinary text because it's so short.",
                        line=lineno)
                    self.parent += msg
                raise statemachine.TransitionCorrection('text')
            else:
                blocktext = context[0] + '\n' + self.state_machine.line
                msg = self.reporter.warning(
                    'Title underline too short.',
                    nodes.literal_block(blocktext, blocktext), line=lineno)
                messages.append(msg)
        if not self.state_machine.match_titles:
            blocktext = context[0] + '\n' + self.state_machine.line
            msg = self.reporter.severe(
                'Unexpected section title.',
                nodes.literal_block(blocktext, blocktext), line=lineno)
            self.parent += messages
            self.parent += msg
            return [], next_state, []
        style = underline[0]
        context[:] = []
        self.section(title, source, style, lineno - 1, messages)
        return [], next_state, []

    def text(self, match, context, next_state):
        """Paragraph."""
        startline = self.state_machine.abs_line_number() - 1
        msg = None
        try:
            block = self.state_machine.get_text_block(flush_left=1)
        except statemachine.UnexpectedIndentationError, instance:
            block, source, lineno = instance.args
            msg = self.reporter.error('Unexpected indentation.',
                                      source=source, line=lineno)
        lines = context + list(block)
        paragraph, literalnext = self.paragraph(lines, startline)
        self.parent += paragraph
        self.parent += msg
        if literalnext:
            try:
                self.state_machine.next_line()
            except EOFError:
                pass
            self.parent += self.literal_block()
        return [], next_state, []

    def literal_block(self):
        """Return a list of nodes."""
        indented, indent, offset, blank_finish = \
              self.state_machine.get_indented()
        nodelist = []
        while indented and not indented[-1].strip():
            indented.trim_end()
        if indented:
            data = '\n'.join(indented)
            nodelist.append(nodes.literal_block(data, data))
            if not blank_finish:
                nodelist.append(self.unindent_warning('Literal block'))
        else:
            nodelist.append(self.reporter.warning(
                  'Literal block expected; none found.',
                  line=self.state_machine.abs_line_number()))
        return nodelist

    def definition_list_item(self, termline):
        indented, indent, line_offset, blank_finish = \
              self.state_machine.get_indented()
        definitionlistitem = nodes.definition_list_item(
            '\n'.join(termline + list(indented)))
        termlist, messages = self.term(
              termline, self.state_machine.abs_line_number() - 1)
        definitionlistitem += termlist
        definition = nodes.definition('', *messages)
        definitionlistitem += definition
        if termline[0][-2:] == '::':
            definition += self.reporter.info(
                  'Blank line missing before literal block? Interpreted as a '
                  'definition list item.', line=line_offset + 1)
        self.nested_parse(indented, input_offset=line_offset, node=definition)
        return definitionlistitem, blank_finish

    def term(self, lines, lineno):
        """Return a definition_list's term and optional classifier."""
        assert len(lines) == 1
        text_nodes, messages = self.inline_text(lines[0], lineno)
        term_node = nodes.term()
        node_list = [term_node]
        for i in range(len(text_nodes)):
            node = text_nodes[i]
            if isinstance(node, nodes.Text):
                parts = node.rawsource.split(' : ', 1)
                if len(parts) == 1:
                    term_node += node
                else:
                    term_node += nodes.Text(parts[0].rstrip())
                    classifier_node = nodes.classifier('', parts[1])
                    classifier_node += text_nodes[i+1:]
                    node_list.append(classifier_node)
                    break
            else:
                term_node += node
        return node_list, messages


class SpecializedText(Text):

    """
    Superclass for second and subsequent lines of Text-variants.

    All transition methods are disabled. Override individual methods in
    subclasses to re-enable.
    """

    def eof(self, context):
        """Incomplete construct."""
        return []

    def invalid_input(self, match=None, context=None, next_state=None):
        """Not a compound element member. Abort this state machine."""
        raise EOFError

    blank = invalid_input
    indent = invalid_input
    underline = invalid_input
    text = invalid_input


class Definition(SpecializedText):

    """Second line of potential definition_list_item."""

    def eof(self, context):
        """Not a definition."""
        self.state_machine.previous_line(2) # so parent SM can reassess
        return []

    def indent(self, match, context, next_state):
        """Definition list item."""
        definitionlistitem, blank_finish = self.definition_list_item(context)
        self.parent += definitionlistitem
        self.blank_finish = blank_finish
        return [], 'DefinitionList', []


class Line(SpecializedText):

    """
    Second line of over- & underlined section title or transition marker.
    """

    eofcheck = 1                        # @@@ ???
    """Set to 0 while parsing sections, so that we don't catch the EOF."""

    def eof(self, context):
        """Transition marker at end of section or document."""
        marker = context[0].strip()
        if len(marker) < 4:
            self.state_correction(context)
        if self.eofcheck:               # ignore EOFError with sections
            lineno = self.state_machine.abs_line_number() - 1
            transition = nodes.transition(context[0])
            transition.line = lineno
            self.parent += transition
            msg = self.reporter.error(
                  'Document or section may not end with a transition.',
                  line=lineno)
            self.parent += msg
        self.eofcheck = 1
        return []

    def blank(self, match, context, next_state):
        """Transition marker."""
        lineno = self.state_machine.abs_line_number() - 1
        marker = context[0].strip()
        if len(marker) < 4:
            self.state_correction(context)
        transition = nodes.transition(marker)
        transition.line = lineno
        if len(self.parent) == 0:
            msg = self.reporter.error(
                  'Document or section may not begin with a transition.',
                  line=lineno)
            self.parent += msg
        elif isinstance(self.parent[-1], nodes.transition):
            msg = self.reporter.error(
                  'At least one body element must separate transitions; '
                  'adjacent transitions not allowed.',
                  line=lineno)
            self.parent += msg
        self.parent += transition
        return [], 'Body', []

    def text(self, match, context, next_state):
        """Potential over- & underlined title."""
        lineno = self.state_machine.abs_line_number() - 1
        overline = context[0]
        title = match.string
        underline = ''
        try:
            underline = self.state_machine.next_line()
        except EOFError:
            blocktext = overline + '\n' + title
            if len(overline.rstrip()) < 4:
                self.short_overline(context, blocktext, lineno, 2)
            else:
                msg = self.reporter.severe(
                    'Incomplete section title.',
                    nodes.literal_block(blocktext, blocktext), line=lineno)
                self.parent += msg
                return [], 'Body', []
        source = '%s\n%s\n%s' % (overline, title, underline)
        overline = overline.rstrip()
        underline = underline.rstrip()
        if not self.transitions['underline'][0].match(underline):
            blocktext = overline + '\n' + title + '\n' + underline
            if len(overline.rstrip()) < 4:
                self.short_overline(context, blocktext, lineno, 2)
            else:
                msg = self.reporter.severe(
                    'Missing underline for overline.',
                    nodes.literal_block(source, source), line=lineno)
                self.parent += msg
                return [], 'Body', []
        elif overline != underline:
            blocktext = overline + '\n' + title + '\n' + underline
            if len(overline.rstrip()) < 4:
                self.short_overline(context, blocktext, lineno, 2)
            else:
                msg = self.reporter.severe(
                      'Title overline & underline mismatch.',
                      nodes.literal_block(source, source), line=lineno)
                self.parent += msg
                return [], 'Body', []
        title = title.rstrip()
        messages = []
        if len(title) > len(overline):
            blocktext = overline + '\n' + title + '\n' + underline
            if len(overline.rstrip()) < 4:
                self.short_overline(context, blocktext, lineno, 2)
            else:
                msg = self.reporter.warning(
                      'Title overline too short.',
                      nodes.literal_block(source, source), line=lineno)
                messages.append(msg)
        style = (overline[0], underline[0])
        self.eofcheck = 0               # @@@ not sure this is correct
        self.section(title.lstrip(), source, style, lineno + 1, messages)
        self.eofcheck = 1
        return [], 'Body', []

    indent = text                       # indented title

    def underline(self, match, context, next_state):
        overline = context[0]
        blocktext = overline + '\n' + self.state_machine.line
        lineno = self.state_machine.abs_line_number() - 1
        if len(overline.rstrip()) < 4:
            self.short_overline(context, blocktext, lineno, 1)
        msg = self.reporter.error(
              'Invalid section title or transition marker.',
              nodes.literal_block(blocktext, blocktext), line=lineno)
        self.parent += msg
        return [], 'Body', []

    def short_overline(self, context, blocktext, lineno, lines=1):
        msg = self.reporter.info(
            'Possible incomplete section title.\nTreating the overline as '
            "ordinary text because it's so short.", line=lineno)
        self.parent += msg
        self.state_correction(context, lines)

    def state_correction(self, context, lines=1):
        self.state_machine.previous_line(lines)
        context[:] = []
        raise statemachine.StateCorrection('Body', 'text')


state_classes = (Body, BulletList, DefinitionList, EnumeratedList, FieldList,
                 OptionList, ExtensionOptions, Explicit, Text, Definition,
                 Line, SubstitutionDef, RFC2822Body, RFC2822List)
"""Standard set of State classes used to start `RSTStateMachine`."""


def escape2null(text):
    """Return a string with escape-backslashes converted to nulls."""
    parts = []
    start = 0
    while 1:
        found = text.find('\\', start)
        if found == -1:
            parts.append(text[start:])
            return ''.join(parts)
        parts.append(text[start:found])
        parts.append('\x00' + text[found+1:found+2])
        start = found + 2               # skip character after escape

def unescape(text, restore_backslashes=0):
    """Return a string with nulls removed or restored to backslashes."""
    if restore_backslashes:
        return text.replace('\x00', '\\')
    else:
        return ''.join(text.split('\x00'))