# encoding: utf-8

module DText
  def parse(str)
    return "" unless str

    state = ["newline"]
    result = ""

    # Normalize newlines.
    str.strip!
    str.gsub!(/(\r\n?)/, "\n")
    str.gsub!(/\n{3,}/, "\n\n")
    str = CGI.escapeHTML str

    # Nuke spaces between newlines.
    str.gsub!(/ *\n */, "\n")
    # Keep newline, use carriage return for split.
    str.gsub!("\n", "\n\r")
    data = str.split("\r")

    # Parse header and list first, line by line.
    data.each do |d|
      result << parseline(d, state)
    end

    # Parse inline tags as a whole.
    result = parseinline(result)

    # Nokogiri ensures valid html output.
    Nokogiri::HTML::DocumentFragment.parse(result).to_html
  end

  def parseinline(str)
    # Short links subtitution:
    str.gsub!(/\[\[(.+?)\]\]/) do # [[title]] or [[title|label]] ;link to wiki
      data = Regexp.last_match[1].split("|", 2)
      title = data[0]
      label = data[1].nil? ? title : data[1]
      "<a href=\"/wiki/show?title=#{CGI.escape(CGI.unescapeHTML(title.tr(" ", "_")))}\">#{label}</a>"
    end
    str.gsub!(/\{\{(.+?)\}\}/) do # {{post tags here}} ;search post with tags
      "<a href=\"/post?tags=#{CGI.escape(CGI.unescapeHTML(Regexp.last_match[1]))}\">#{Regexp.last_match[1]}</a>"
    end

    # Miscellaneous single line tags subtitution.
    str.gsub! /\[b\](.+?)\[\/b\]/, '<strong>\1</strong>'
    str.gsub! /\[i\](.+?)\[\/i\]/, '<em>\1</em>'
    str.gsub! /(post #(\d+))/i, '<a href="/post/show/\2">\1</a>'
    str.gsub! /(forum #(\d+))/i, '<a href="/forum/show/\2">\1</a>'
    str.gsub! /(comment #(\d+))/i, '<a href="/comment/show/\2">\1</a>'
    str.gsub! /(pool #(\d+))/i, '<a href="/pool/show/\2">\1</a>'

    # Single line spoiler tags.
    str.gsub! /\[spoilers?\](.+?)\[\/spoilers?\]/, '<span class="spoiler js-comment--spoiler"><span class="spoilerwarning">spoiler</span></span><span class="spoilertext" style="display: none">\1</span>'
    str.gsub! /\[spoilers?=(.+?)\](.+?)\[\/spoilers?\]/, '<span class="spoiler js-comment--spoiler"><span class="spoilerwarning">\1</span></span><span class="spoilertext" style="display: none">\2</span>'

    # Multi line spoiler tags.
    str.gsub! /\[spoilers?\]/, '<span class="spoiler js-comment--spoiler"><span class="spoilerwarning">spoiler</span></span><div class="spoilertext" style="display: none">'
    str.gsub! /\[spoilers?=(.+?)\]/, '<span class="spoiler js-comment--spoiler"><span class="spoilerwarning">\1</span></span><div class="spoilertext" style="display: none">'
    str.gsub! /\[\/spoilers?\]/, "</div>"

    # Quote.
    str.gsub! /\[quote\]/, "<blockquote><div>"
    str.gsub! /\[\/quote\]/, "</div></blockquote>"

    str = parseurl(str)

    # Extraneous newlines before closing div are unnecessary.
    str.gsub! /\n+(<\/div>)/, '\1'
    # So are after headers, lists, and blockquotes.
    str.gsub! /(<\/(ul|h\d+|blockquote)>)\n+/, '\1'
    # And after opening blockquote.
    str.gsub! /(<blockquote><div>)\n+/, '\1'
    str.gsub! /\n/, "<br>"
    str
  end

  def parseline(str, state)
    if state.last =~ /\d/ || str =~ /^\*+\s+/
      parselist str, state
    elsif str =~ /^(h[1-6])\.\s*(.+)\n*/
      "<#{Regexp.last_match[1]}>#{Regexp.last_match[2]}</#{Regexp.last_match[1]}>"
    else
      str
    end
  end

  def parselist(str, state)
    html = ""
    if state.last =~ /\d/
      n = ((str =~ /^\*+\s+/ && str.split[0]) || "").count("*")
      if n < state.last.to_i
        html << "</ul>" * (state.last.to_i - n)
        state[-1] = n.to_s
      elsif n > state.last.to_i
        html << "<ul>"
        state[-1] = (state.last.to_i + 1).to_s
      end
      unless str =~ /^\*+\s+/
        state.pop
        return html + parseline(str, state)
      end
    else
      state.push "1"
      html << "<ul>"
    end
    html << str.gsub(/\*+\s+(.+)\n*/, '<li>\1')
  end

  def parseurl(str)
    # url
    str.gsub! %r{(^|[\s\(>])(h?ttps?://(?:(?!&gt;&gt;)[^\s<"])+[^\s<".])}, '\1<a href="\2">\2</a>'

    # <<url|label>>
    str.gsub! %r{&lt;&lt;(h?ttps?://(?:(?!&gt;&gt;).)+)\|((?:(?!&gt;&gt;).)+)&gt;&gt;}, '<a href="\1">\2</a>'

    # <<url>>
    str.gsub! %r{&lt;&lt;(h?ttps?:\/\/(?:(?!&gt;&gt;).)+)&gt;&gt;}, '<a href="\1">\1</a>'

    # "label":url
    str.gsub! %r{(^|[\s>])&quot;((?:(?!&quot;).)+)&quot;:(h?ttps?://[^\s<"]+[^\s<".])}, '\1<a href="\3">\2</a>'

    # Fix ttp(s) scheme
    str.gsub! /<a href="ttp/, '<a href="http'
    str
  end

  module_function :parse, :parseline, :parseinline, :parselist, :parseurl
end