module GitlabMarkdownHelper
  def gfm(text, html_options = {})
    return text if text.nil?
    return text if @project.nil?

    # Extract pre blocks
    # from http://github.github.com/github-flavored-markdown/
    extractions = {}
    text.gsub!(%r{<pre>.*?</pre>|<code>.*?</code>}m) do |match|
      md5 = Digest::MD5.hexdigest(match)
      extractions[md5] = match
      "{gfm-extraction-#{md5}}"
    end

    # match     1    2 3               4     5            6
    text.gsub!(/(\W)?(@([\w\._]+)|[#!$](\d+)|([\h]{6,40}))(\W)?/) do |match|
      prefix    = $1
      reference = $2
      user_name = $3
      issue_id  = $4
      merge_request_id = $4
      snippet_id = $4
      commit_id = $5
      suffix    = $6

      # TODO: add popups with additional information
      ref_link = case reference

                  # team member: @foo
                  when /^@/
                    user = @project.users.where(:name => user_name).first
                    member = @project.users_projects.where(:user_id => user).first if user
                    link_to("@#{user_name}", project_team_member_path(@project, member), html_options.merge(:class => "gfm gfm-team_member #{html_options[:class]}")) if member

                  # issue: #123
                  when /^#/
                    # avoid HTML entities
                    unless prefix.try(:end_with?, "&") && suffix.try(:start_with?, ";")
                      issue = @project.issues.where(:id => issue_id).first
                      link_to("##{issue_id}", project_issue_path(@project, issue), html_options.merge(:title => "Issue: #{issue.title}", :class => "gfm gfm-issue #{html_options[:class]}")) if issue
                    end

                  # merge request: !123
                  when /^!/
                    merge_request = @project.merge_requests.where(:id => merge_request_id).first
                    link_to("!#{merge_request_id}", project_merge_request_path(@project, merge_request), html_options.merge(:title => "Merge Request: #{merge_request.title}", :class => "gfm gfm-merge_request #{html_options[:class]}")) if merge_request

                  # snippet: $123
                  when /^\$/
                    snippet = @project.snippets.where(:id => snippet_id).first
                    link_to("$#{snippet_id}", project_snippet_path(@project, snippet), html_options.merge(:title => "Snippet: #{snippet.title}", :class => "gfm gfm-snippet #{html_options[:class]}")) if snippet

                  # commit: 123456...
                  when /^\h/
                    commit = @project.commit(commit_id)
                    link_to(commit_id, project_commit_path(@project, :id => commit.id), html_options.merge(:title => "Commit: #{commit.author_name} - #{CommitDecorator.new(commit).title}", :class => "gfm gfm-commit #{html_options[:class]}")) if commit

                  end # case

      ref_link.nil? ? match : "#{prefix}#{ref_link}#{suffix}"
    end # gsub

    # Insert pre block extractions
    text.gsub!(/\{gfm-extraction-(\h{32})\}/) do
      extractions[$1]
    end

    text.html_safe
  end

  # circumvents nesting links, which will behave bad in browsers
  def link_to_gfm(body, url, html_options = {})
    gfm_body = gfm(body, html_options)

    gfm_body.gsub!(%r{<a.*?>.*?</a>}m) do |match|
      "</a>#{match}#{link_to("", url, html_options)[0..-5]}" # "</a>".length +1
    end

    link_to(gfm_body.html_safe, url, html_options)
  end
end