discourse/lib/discourse_diff.rb

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# frozen_string_literal: true
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class DiscourseDiff
MAX_DIFFERENCE = 200
def initialize(before, after)
@before = before
@after = after
before_html = tokenize_html_blocks(@before)
after_html = tokenize_html_blocks(@after)
before_markdown = tokenize_line(CGI::escapeHTML(@before))
after_markdown = tokenize_line(CGI::escapeHTML(@after))
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@block_by_block_diff = ONPDiff.new(before_html, after_html).paragraph_diff
@line_by_line_diff = ONPDiff.new(before_markdown, after_markdown).short_diff
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end
def inline_html
i = 0
inline = []
while i < @block_by_block_diff.size
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op_code = @block_by_block_diff[i][1]
if op_code == :common then inline << @block_by_block_diff[i][0]
else
if op_code == :delete
opposite_op_code = :add
klass = "del"
first = i
second = i + 1
else
opposite_op_code = :delete
klass = "ins"
first = i + 1
second = i
end
if i + 1 < @block_by_block_diff.size && @block_by_block_diff[i + 1][1] == opposite_op_code
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diff = ONPDiff.new(tokenize_html(@block_by_block_diff[first][0]), tokenize_html(@block_by_block_diff[second][0])).diff
inline << generate_inline_html(diff)
i += 1
else
inline << add_class_or_wrap_in_tags(@block_by_block_diff[i][0], klass)
end
end
i += 1
end
"<div class=\"inline-diff\">#{inline.join}</div>"
end
def side_by_side_html
i = 0
left, right = [], []
while i < @block_by_block_diff.size
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op_code = @block_by_block_diff[i][1]
if op_code == :common
left << @block_by_block_diff[i][0]
right << @block_by_block_diff[i][0]
else
if op_code == :delete
opposite_op_code = :add
side = left
klass = "del"
first = i
second = i + 1
else
opposite_op_code = :delete
side = right
klass = "ins"
first = i + 1
second = i
end
if i + 1 < @block_by_block_diff.size && @block_by_block_diff[i + 1][1] == opposite_op_code
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diff = ONPDiff.new(tokenize_html(@block_by_block_diff[first][0]), tokenize_html(@block_by_block_diff[second][0])).diff
deleted, inserted = generate_side_by_side_html(diff)
left << deleted
right << inserted
i += 1
else
side << add_class_or_wrap_in_tags(@block_by_block_diff[i][0], klass)
end
end
i += 1
end
"<div class=\"revision-content\">#{left.join}</div><div class=\"revision-content\">#{right.join}</div>"
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end
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def side_by_side_markdown
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i = 0
table = ["<table class=\"markdown\">"]
while i < @line_by_line_diff.size
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table << "<tr>"
op_code = @line_by_line_diff[i][1]
if op_code == :common
table << "<td>#{@line_by_line_diff[i][0]}</td>"
table << "<td>#{@line_by_line_diff[i][0]}</td>"
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else
if op_code == :delete
opposite_op_code = :add
first = i
second = i + 1
else
opposite_op_code = :delete
first = i + 1
second = i
end
if i + 1 < @line_by_line_diff.size && @line_by_line_diff[i + 1][1] == opposite_op_code
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before_tokens, after_tokens = tokenize_markdown(@line_by_line_diff[first][0]), tokenize_markdown(@line_by_line_diff[second][0])
if (before_tokens.size - after_tokens.size).abs > MAX_DIFFERENCE
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before_tokens, after_tokens = tokenize_line(@line_by_line_diff[first][0]), tokenize_line(@line_by_line_diff[second][0])
end
diff = ONPDiff.new(before_tokens, after_tokens).short_diff
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deleted, inserted = generate_side_by_side_markdown(diff)
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table << "<td class=\"diff-del\">#{deleted.join}</td>"
table << "<td class=\"diff-ins\">#{inserted.join}</td>"
i += 1
else
if op_code == :delete
table << "<td class=\"diff-del\">#{@line_by_line_diff[i][0]}</td>"
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table << "<td></td>"
else
table << "<td></td>"
table << "<td class=\"diff-ins\">#{@line_by_line_diff[i][0]}</td>"
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end
end
end
table << "</tr>"
i += 1
end
table << "</table>"
table.join
end
private
def tokenize_line(text)
text.scan(/[^\r\n]+[\r\n]*/)
end
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def tokenize_markdown(text)
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t, tokens = [], []
i = 0
while i < text.size
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if text[i] =~ /\w/
t << text[i]
elsif text[i] =~ /[ \t]/ && t.join =~ /^\w+$/
begin
t << text[i]
i += 1
end while i < text.size && text[i] =~ /[ \t]/
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i -= 1
tokens << t.join
t = []
else
tokens << t.join if t.size > 0
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tokens << text[i]
t = []
end
i += 1
end
tokens << t.join if t.size > 0
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tokens
end
def tokenize_html_blocks(html)
Nokogiri::HTML.fragment(html).search("./*").map(&:to_html)
end
def tokenize_html(html)
HtmlTokenizer.tokenize(html)
end
def add_class_or_wrap_in_tags(html_or_text, klass)
result = html_or_text.dup
index_of_next_chevron = result.index(">")
if result.size > 0 && result[0] == '<' && index_of_next_chevron
index_of_class = result.index("class=")
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if index_of_class.nil? || index_of_class > index_of_next_chevron
# we do not have a class for the current tag
# add it right before the ">"
result.insert(index_of_next_chevron, " class=\"diff-#{klass}\"")
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else
# we have a class, insert it at the beginning if not already present
classes = result[/class=(["'])([^\1]*)\1/, 2]
if classes.include?("diff-#{klass}")
result
else
result.insert(index_of_class + "class=".size + 1, "diff-#{klass} ")
end
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end
else
"<#{klass}>#{result}</#{klass}>"
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end
end
def generate_inline_html(diff)
inline = []
diff.each do |d|
case d[1]
when :common then inline << d[0]
when :delete then inline << add_class_or_wrap_in_tags(d[0], "del")
when :add then inline << add_class_or_wrap_in_tags(d[0], "ins")
end
end
inline
end
def generate_side_by_side_html(diff)
deleted, inserted = [], []
diff.each do |d|
case d[1]
when :common
deleted << d[0]
inserted << d[0]
when :delete then deleted << add_class_or_wrap_in_tags(d[0], "del")
when :add then inserted << add_class_or_wrap_in_tags(d[0], "ins")
end
end
[deleted, inserted]
end
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def generate_side_by_side_markdown(diff)
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deleted, inserted = [], []
diff.each do |d|
case d[1]
when :common
deleted << d[0]
inserted << d[0]
when :delete then deleted << "<del>#{d[0]}</del>"
when :add then inserted << "<ins>#{d[0]}</ins>"
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end
end
[deleted, inserted]
end
class HtmlTokenizer < Nokogiri::XML::SAX::Document
attr_accessor :tokens
def initialize
@tokens = []
end
def self.tokenize(html)
me = new
parser = Nokogiri::HTML::SAX::Parser.new(me)
parser.parse("<html><body>#{html}</body></html>")
me.tokens
end
USELESS_TAGS = %w{html body}
def start_element(name, attributes = [])
return if USELESS_TAGS.include?(name)
attrs = attributes.map { |a| " #{a[0]}=\"#{a[1]}\"" }.join
@tokens << "<#{name}#{attrs}>"
end
AUTOCLOSING_TAGS = %w{area base br col embed hr img input meta}
def end_element(name)
return if USELESS_TAGS.include?(name) || AUTOCLOSING_TAGS.include?(name)
@tokens << "</#{name}>"
end
def characters(string)
@tokens.concat string.scan(/\W|\w+[ \t]*/).map { |x| CGI::escapeHTML(x) }
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end
end
end