discourse/lib/email/html_cleaner.rb

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module Email
# HtmlCleaner cleans up the extremely dirty HTML that many email clients
# generate by stripping out any excess divs or spans, removing styling in
# the process (which also makes the html more suitable to be parsed as
# Markdown).
class HtmlCleaner
# Elements to hoist all children out of
HTML_HOIST_ELEMENTS = %w(div span font table tbody th tr td)
# Node types to always delete
HTML_DELETE_ELEMENT_TYPES = [
Nokogiri::XML::Node::DTD_NODE,
Nokogiri::XML::Node::COMMENT_NODE,
]
# Private variables:
# @doc - nokogiri document
# @out - same as @doc, but only if trimming has occured
def initialize(html)
if String === html
@doc = Nokogiri::HTML(html)
else
@doc = html
end
end
class << self
# Email::HtmlCleaner.trim(inp, opts={})
#
# Arguments:
# inp - Either a HTML string or a Nokogiri document.
# Options:
# :return => :doc, :string
# Specify the desired return type.
# Defaults to the type of the input.
# A value of :string is equivalent to calling get_document_text()
# on the returned document.
def trim(inp, opts={})
cleaner = HtmlCleaner.new(inp)
opts[:return] ||= ((String === inp) ? :string : :doc)
if opts[:return] == :string
cleaner.output_html
else
cleaner.output_document
end
end
# Email::HtmlCleaner.get_document_text(doc)
#
# Get the body portion of the document, including html, as a string.
def get_document_text(doc)
body = doc.xpath('//body')
if body
body.inner_html
else
doc.inner_html
end
end
end
def output_document
@out ||= begin
doc = @doc
trim_process_node doc
add_newlines doc
doc
end
end
def output_html
HtmlCleaner.get_document_text(output_document)
end
private
def add_newlines(doc)
# Replace <br> tags with a markdown \n
doc.xpath('//br').each do |br|
br.replace(new_linebreak_node doc, 2)
end
# Surround <p> tags with newlines, to help with line-wise postprocessing
# and ensure markdown paragraphs
doc.xpath('//p').each do |p|
p.before(new_linebreak_node doc)
p.after(new_linebreak_node doc, 2)
end
end
def new_linebreak_node(doc, count=1)
Nokogiri::XML::Text.new("\n" * count, doc)
end
def trim_process_node(node)
if should_hoist?(node)
hoisted = trim_hoist_element node
hoisted.each { |child| trim_process_node child }
elsif should_delete?(node)
node.remove
else
if children = node.children
children.each { |child| trim_process_node child }
end
end
node
end
def trim_hoist_element(element)
hoisted = []
element.children.each do |child|
element.before(child)
hoisted << child
end
element.remove
hoisted
end
def should_hoist?(node)
return false unless node.element?
HTML_HOIST_ELEMENTS.include? node.name
end
def should_delete?(node)
return true if HTML_DELETE_ELEMENT_TYPES.include? node.type
return true if node.element? && node.name == 'head'
return true if node.text? && node.text.strip.blank?
false
end
end
end