transcoder.rb

# frozen_string_literal: true

require 'timeout'

require_relative 'media'

module FFMPEG
  # The Transcoder class is responsible for transcoding multimedia files
  # via preset configurations.
  #
  # @example
  #  transcoder = FFMPEG::Transcoder.new(
  #    presets: [FFMPEG::Presets.h264_360p_30, FFMPEG::Presets.aac_128k]
  #  )
  #  status = transcoder.process('input.mp4', 'output') do |report|
  #    puts(report)
  #  end
  #  status.paths # ['output.360p30.mp4', 'output.128k.aac']
  #  status.media # [FFMPEG::Media, FFMPEG::Media]
  #  status.success? # true
  #  status.exitstatus # 0
  class Transcoder
    # The Status class represents the status of a transcoding process.
    # It inherits all methods from the FFMPEG::Status class.
    # It also provides a method to retrieve the media files associated with
    # the transcoding process.
    class Status < FFMPEG::Status
      attr_reader :paths

      def initialize(paths, checks: %i[exist?])
        @paths = paths
        @checks = checks
        super()
      end

      # Returns true if the transcoding process was successful.
      # It returns true if the process exited with a zero exit status
      # and all checks passed.
      #
      # @return [Boolean] True if the transcoding process was successful, false otherwise.
      def success?
        return false unless super

        @checks.all? do |check|
          if check.is_a?(Symbol) && respond_to?(check)
            send(check)
          elsif check.respond_to?(:call)
            check.call(self)
          else
            raise ArgumentError, "Unknown check format #{check.class}, expected #{Symbol} or #{Proc}"
          end
        end
      end

      # Returns the media files associated with the transcoding process.
      #
      # @param ffprobe_args [Array<String>] The arguments to pass to ffprobe.
      # @param load [Boolean] Whether to load the media files.
      # @param autoload [Boolean] Whether to autoload the media files.
      # @return [Array<FFMPEG::Media>] The media files.
      def media(*ffprobe_args, load: true, autoload: true)
        @paths.map do |path|
          Media.new(path, *ffprobe_args, load: load, autoload: autoload)
        end
      end

      # Returns true if all output paths exist.
      #
      # @return [Boolean] True if all output paths exist, false otherwise.
      def exist?
        @paths.all? { |path| File.exist?(path) }
      end
    end

    attr_reader :name, :metadata, :presets, :reporters, :checks, :retries, :timeout

    def initialize(
      name: nil,
      metadata: nil,
      presets: [],
      reporters: nil,
      checks: %i[exist?],
      retries: nil,
      timeout: nil,
      &compose_inargs
    )
      @name = name
      @metadata = metadata
      @presets = presets
      @reporters = reporters
      @checks = checks
      @retries = retries&.abs || 0
      @timeout = timeout
      @compose_inargs = compose_inargs
    end

    # Transcodes the media file using the preset configurations.
    #
    # @param media [String, Pathname, URI, FFMPEG::Media] The media file to transcode.
    # @param output_path [String, Pathname] The output path to save the transcoded files.
    # @param chdir [String, Pathname] Change the ffmpeg working directory
    # @yield The block to execute to report the transcoding process.
    # @return [FFMPEG::Transcoder::Status] The status of the transcoding process.
    def process(media, output_path, chdir: nil, &)
      status = nil

      attempts = 0
      while attempts <= @retries
        media = Media.new(media, load: false) unless media.is_a?(Media)
        context = { attempts: }
        context[:retry] = true if attempts.positive?

        output_paths = []
        output_path = Pathname.new(output_path)
        output_dir = output_path.dirname
        output_filename_kwargs = {
          basename: output_path.basename(output_path.extname),
          extname: output_path.extname
        }

        args = []
        @presets.each do |preset|
          filename = preset.filename(**output_filename_kwargs)
          args += preset.args(media, context:)
          args << (filename.nil? ? output_path.to_s : output_dir.join(filename).to_s)
          output_paths << args.last
        end

        inargs = CommandArgs.compose(media, context:, &@compose_inargs).to_a
        spawn = chdir ? { chdir: } : {}
        status = media.ffmpeg_execute(
          *args,
          inargs:,
          reporters:,
          timeout:,
          spawn:,
          status: Status.new(output_paths, checks:),
          &
        )

        return status if status.success?

        attempts += 1
      end

      status
    end

    # Transcodes the media file using the preset configurations,
    # raising an error if the subprocess did not finish successfully.
    #
    # @param media [String, Pathname, URI, FFMPEG::Media] The media file to transcode.
    # @param output_path [String, Pathname] The output path to save the transcoded files.
    # @param chdir [String, Pathname] Change the ffmpeg working directory
    # @yield The block to execute to report the transcoding process.
    # @return [FFMPEG::Transcoder::Status] The status of the transcoding process.
    def process!(media, output_path, chdir: nil, &)
      process(media, output_path, chdir:, &).assert!
    end
  end
end