module Onebox
  module Engine
    class YoutubeOnebox
      include Engine
      include StandardEmbed

      matches_regexp(/^https?:\/\/(?:www\.)?(?:m\.)?(?:youtube\.com|youtu\.be)\/.+$/)
      always_https

      WIDTH  ||= 480
      HEIGHT ||= 360

      def placeholder_html
        if video_id
          "<img src='https://i.ytimg.com/vi/#{video_id}/hqdefault.jpg' width='#{WIDTH}' height='#{HEIGHT}' #{Helpers.title_attr(video_oembed_data)}>"
        elsif list_id
          "<img src='#{list_thumbnail_url}' width='#{WIDTH}' height='#{HEIGHT}' #{Helpers.title_attr(list_oembed_data)}>"
        else
          to_html
        end
      end

      def to_html
        if video_id
          <<-HTML
            <iframe width="#{WIDTH}"
                    height="#{HEIGHT}"
                    src="https://www.youtube.com/embed/#{video_id}?#{embed_params}"
                    frameborder="0"
                    allowfullscreen>
            </iframe>
          HTML
        elsif list_id
          <<-HTML
            <iframe width="#{WIDTH}"
                    height="#{HEIGHT}"
                    src="https://www.youtube.com/embed/videoseries?list=#{list_id}&wmode=transparent&rel=0&autohide=1&showinfo=1&enablejsapi=1"
                    frameborder="0"
                    allowfullscreen>
            </iframe>
          HTML
        else
          # for channel pages
          html = Onebox::Engine::WhitelistedGenericOnebox.new(@url, @cache, @timeout).to_html
          return if Onebox::Helpers.blank?(html)
          html.gsub!(/['"]\/\//, "https://")
          html
        end
      end

      def video_title
        @video_title ||= begin
          Onebox::Helpers.truncate(video_oembed_data[:title], 80)
        rescue
          nil
        end
      end

      private

      def video_id
        @video_id ||= begin
          # http://youtu.be/afyK1HSFfgw
          if uri.host["youtu.be"]
            id = uri.path[/\/([\w\-]+)/, 1]
            return id if id
          end

          # https://www.youtube.com/embed/vsF0K3Ou1v0
          if uri.path["/embed/"]
            id = uri.path[/\/embed\/([\w\-]+)/, 1]
            return id if id
          end

          # https://www.youtube.com/watch?v=Z0UISCEe52Y
          params['v']
        end
      end

      def list_id
        @list_id ||= params['list']
      end

      def list_thumbnail_url
        @list_thumbnail_url ||= begin
          url = "https://www.youtube.com/oembed?format=json&url=https://www.youtube.com/playlist?list=#{list_id}"
          response = Onebox::Helpers.fetch_response(url) rescue "{}"
          data = Onebox::Helpers.symbolize_keys(::MultiJson.load(response))
          data[:thumbnail_url]
        rescue
          nil
        end
      end

      def video_oembed_data
        url = "https://www.youtube.com/oembed?format=json&url=https://www.youtube.com/watch?v=#{video_id}"
        response = Onebox::Helpers.fetch_response(url) rescue "{}"
        Onebox::Helpers.symbolize_keys(::MultiJson.load(response))
      end

      def list_oembed_data
        url = "https://www.youtube.com/oembed?format=json&url=https://www.youtube.com/playlist?list=#{list_id}"
        response = Onebox::Helpers.fetch_response(url) rescue "{}"
        Onebox::Helpers.symbolize_keys(::MultiJson.load(response))
      end

      def embed_params
        p = { 'feature' => 'oembed', 'wmode' => 'opaque' }

        p['list'] = list_id if list_id

        # Parse timestrings, and assign the result as a start= parameter
        start = if params['start']
          params['start']
        elsif params['t']
          params['t']
        elsif uri.fragment && uri.fragment.start_with?('t=')
          # referencing uri is safe here because any throws were already caught by video_id returning nil
          # remove the t= from the start
          uri.fragment[2..-1]
        end

        p['start'] = parse_timestring(start)        if start
        p['end']   = parse_timestring params['end'] if params['end']

        # Official workaround for looping videos
        # https://developers.google.com/youtube/player_parameters#loop
        # use params.include? so that you can just add "&loop"
        if params.include?('loop')
          p['loop'] = 1
          p['playlist'] = video_id
        end

        # https://developers.google.com/youtube/player_parameters#rel
        p['rel'] = 0 if params.include?('rel')

        URI.encode_www_form(p)
      end

      def parse_timestring(string)
        if string =~ /(\d+h)?(\d+m)?(\d+s?)?/
          ($1.to_i * 3600) + ($2.to_i * 60) + $3.to_i
        end
      end

      def params
        return {} unless uri.query
        # This mapping is necessary because CGI.parse returns a hash of keys to arrays.
        # And *that* is necessary because querystrings support arrays, so they
        # force you to deal with it to avoid security issues that would pop up
        # if one day it suddenly gave you an array.
        #
        # However, we aren't interested. Just take the first one.
        @params ||= begin
          p = {}
          CGI.parse(uri.query).each { |k, v| p[k] = v.first }
          p
        end
      rescue
        {}
      end

    end
  end
end