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# it is forked from https://github.com/xijo/reverse-markdown/blob/master/reverse_markdown.rb
require 'rexml/document'
require 'benchmark'
include REXML
include Benchmark
class ReverseMarkdown
# set basic variables:
# - @li_counter: numbering list item (li) tags in an ordered list (ol)
# - @links: hold the links for adding them to the bottom of the @output
# this means 'reference style', please take a look at http://daringfireball.net/projects/markdown/syntax#link
# - @outout: fancy markdown code in here!
# - @indent: control indention level for nested lists
# - @errors: appearing errors, like unknown tags, go into this array
def initialize()
@li_counter = 0
@links = []
@output = ""
@indent = 0
@errors = []
end
# Invokes the HTML parsing by using a string. Returns the markdown code in @output.
# To garantuee well-formed xml for REXML a <root> element will be added, but has no effect.
# After parsing all elements, the 'reference style'-links will be inserted.
def parse_string(string)
doc = Document.new("<root>\n"+string+"\n</root>")
root = doc.root
root.elements.each do |element|
parse_element(element, :root)
end
insert_links()
@output
end
# Parsing an element and its children (recursive) and writing its markdown code to @output
# 1. do indent for nested list items
# 2. add the markdown opening tag for this element
# 3a. if element only contains text, handle it like a text node
# 3b. if element is a container handle its children, which may be text- or element nodes
# 4. finally add the markdown ending tag for this element
def parse_element(element, parent)
name = element.name.to_sym
# 1.
@output << indent() if name.eql?(:li)
# 2.
@output << opening(element, parent)
# 3a.
if (element.has_text? and element.children.size < 2)
@output << text_node(element, parent)
end
# 3b.
if element.has_elements?
element.children.each do |child|
# increase indent if nested list
@indent += 1 if element.name=~/(ul|ol)/ and parent.eql?(:li)
if child.node_type.eql?(:element)
parse_element(child, element.name.to_sym)
else
if parent.eql?(:blockquote)
@output << child.to_s.gsub("\n ", "\n>")
else
@output << child.to_s
end
end
# decrease indent if end of nested list
@indent -= 1 if element.name=~/(ul|ol)/ and parent.eql?(:li)
end
end
# 4.
@output << ending(element, parent)
end
# Returns opening markdown tag for the element. Its parent matters sometimes!
def opening(type, parent)
case type.name.to_sym
when :h1
"# "
when :li
parent.eql?(:ul) ? " - " : " "+(@li_counter+=1).to_s+". "
when :ol
@li_counter = 0
""
when :ul
""
when :h2
"## "
when :em
"*"
when :strong
"**"
when :blockquote
# remove leading newline
type.children.first.value = ""
"> "
when :code
parent.eql?(:pre) ? " " : "`"
when :a
"["
when :img
"!["
when :hr
"----------\n\n"
else
@errors << "unknown start tag: "+type.name.to_s
""
end
end
# Returns the closing markdown tag, like opening()
def ending(type, parent)
case type.name.to_sym
when :h1
" #\n\n"
when :h2
" ##\n\n"
when :p
parent.eql?(:root) ? "\n\n" : "\n"
when :ol
parent.eql?(:li) ? "" : "\n"
when :ul
parent.eql?(:li) ? "" : "\n"
when :em
"*"
when :strong
"**"
when :li
""
when :blockquote
""
when :code
parent.eql?(:pre) ? "" : "`"
when :a
@links << type.attribute('href').to_s
"][" + @links.size.to_s + "] "
when :img
@links << type.attribute('src').to_s
"" + type.attribute('alt').to_s + "][" + @links.size.to_s + "] "
"#{type.attribute('alt')}][#{@links.size}] "
else
@errors << " unknown end tag: "+type.name.to_s
""
end
end
# Perform indent: two space, @indent times - quite simple! :)
def indent
str = ""
@indent.times do
str << " "
end
str
end
# Return the content of element, which should be just text.
# If its a code block to indent of 4 spaces.
# For block quotation add a leading '>'
def text_node(element, parent)
if element.name.to_sym.eql?(:code) and parent.eql?(:pre)
element.text.gsub("\n","\n ") << "\n"
elsif parent.eql?(:blockquote)
element.text.gsub!("\n ","\n>")
else
element.text
end
end
# Insert the mentioned reference style links.
def insert_links
@output << "\n"
@links.each_index do |index|
@output << " [#{index+1}]: #{@links[index]}\n"
end
end
# Print out all errors, that occured and have been written to @errors.
def print_errors
@errors.each do |error|
puts error
end
end
# Perform a benchmark on a given string n-times.
def speed_benchmark(string, n)
initialize()
bm(15) do |test|
test.report("reverse markdown:") { n.times do; parse_string(string); initialize(); end; }
end
end
end
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