marked = require 'marked'

# Internal: A class to post-process the best available output from the marked
# library to conform to GHM. In addition the allowed tags can be limited.
module.exports = class Markdown

  # Tags to keep when parsing is limited
  @limitedTags: 'a,abbr,acronym,b,big,cite,code,del,em,i,ins,sub,sup,span,small,strike,strong,q,tt,u'

  # Convert markdown to Html. If the param `limit`
  # is true, then all unwanted elements are stripped from the
  # result and also all existing newlines.
  #
  # markdown - the markdown markup (a {String})
  # limit - if elements should be limited (a {Boolean})
  #
  @convert: (markdown, limit = false, allowed = Markdown.limitedTags) ->
    return if markdown is undefined

    html = marked(markdown)

    if limit
      html = html.replace(/\n/, '')
      html = Markdown.limit(html, allowed)

    # Remove newlines around open and closing paragraph tags
    html = html.replace /(?:\n+)?<(\/?p)>(?:\n+)?/mg, '<$1>'

    html

  # Strips all unwanted tag from the html
  #
  # html - the Html to clean (a {String})
  # allowed - the comma separated list of allowed tags (a {String})
  # Returns the cleaned Html (a {String})
  #
  @limit: (html, allowed) ->
    allowed = allowed.split ','

    html.replace /<([a-z]+)>(.+?)<\/\1>/, (match, tag, text) ->
      if allowed.indexOf(tag) is -1 then text else match