module Bulldog
  module Attachment
    class Video < Base
      handle :video

      #
      # Return the width and height of the named style, as a 2-element
      # array.
      #
      # This runs ffmpeg for, and only for, the original style.
      #
      # +style_name+ defaults to the attribute's #default_style.
      #
      def dimensions(style_name)
        video_tracks(style_name).first.dimensions
      end

      include HasDimensions

      #
      # Return the duration of the named style, as an
      # ActiveSupport::Duration.
      #
      # This runs ffmpeg for, and only for, the original style.
      #
      # +style_name+ defaults to the attribute's #default_style.
      #
      def duration(style_name)
        # TODO: support styles with different durations
        if stream.missing?
          0
        else
          from_examination :original_duration
        end
      end

      #
      # Return the video tracks of the named style, as an array of
      # VideoTrack objects.
      #
      # Each VideoTrack has:
      #
      #  * <tt>#dimension</tt> - the dimensions of the video track,
      #    [width, height].
      #
      def video_tracks(style_name=nil)
        style_name ||= reflection.default_style
        if style_name == :original
          if stream.missing?
            [VideoTrack.new(:dimensions => [2, 2])]
          else
            examine unless @original_video_tracks
            if @original_video_tracks.empty?
              @original_video_tracks << VideoTrack.new(:dimensions => [2, 2])
            end
            @original_video_tracks
          end
        else
          style = reflection.styles[style_name]
          target_dimensions = style[:size].split(/x/).map{|s| s.to_i}
          video_tracks(:original).map do |video_track|
            dimensions = resized_dimensions(dimensions(:original), target_dimensions, style[:filled])
            dimensions.map!{|i| i &= -2}  # some codecs require multiples of 2
            VideoTrack.new(:dimensions => dimensions)
          end
        end
      end

      #
      # Return the video tracks of the named style, as an array of
      # AudioTrack objects.
      #
      # AudioTrack objects do not yet have any useful methods.
      #
      def audio_tracks(style_name)
        examine
        @original_audio_tracks
      end

      storable_attribute :duration    , :per_style => true, :memoize => true

      def unload
        super
        instance_variables.grep(/@original_/).each do |name|
          instance_variable_set(name, nil)
        end
      end

      protected  # ---------------------------------------------------

      #
      # Return the default processor class to use for this attachment.
      #
      def default_processor_type
        :ffmpeg
      end

      private  # -----------------------------------------------------

      #
      # Read the original image metadata with ffmpeg.
      #
      def run_examination
        return false if stream.missing?
        output = `ffmpeg -i #{stream.path} 2>&1`
        parse_output(output)
      end

      def parse_output(output)
        result = false
        @original_duration = 0
        @original_video_tracks = []
        @original_audio_tracks = []
        io = StringIO.new(output)
        while (line = io.gets)
          case line
          when /^Input #0, (.*?), from '(?:.*)':$/
            result = true
          when /^  Duration: (\d+):(\d+):(\d+)\.(\d+)/
            @original_duration = $1.to_i.hours + $2.to_i.minutes + $3.to_i.seconds
          when /Stream #(?:.*?): Video: /
            if $' =~ /(\d+)x(\d+)/
              dimensions = [$1.to_i, $2.to_i]
            end
            @original_video_tracks << VideoTrack.new(:dimensions => dimensions)
          when /Stream #(?:.*?): Audio: (.*?)/
            @original_audio_tracks << AudioTrack.new
          end
        end
        result
      end

      class Track
        def initialize(attributes={})
          attributes.each do |name, value|
            send("#{name}=", value)
          end
        end
      end

      class VideoTrack < Track
        attr_accessor :dimensions
      end

      class AudioTrack < Track
      end
    end
  end
end