#!/usr/bin/env ruby

# giftube – Generates an animated gif from a YouTube url.
#
# Usage:
#
#   giftube [youtube url] [minute:second] [duration]
#
#   ex.
#
#     giftube 'http://www.youtube.com/watch?v=LBRy4HfDuxc' 0:20 5

# Change these configuration options if you'd like
SCALE             = '480:360'
FRAMES_PER_SECOND = '20'

END {
  if __FILE__ == $0
    USAGE = "giftube [youtube url] [minute:second] [duration]"
    abort(USAGE) unless ARGV.size == 3

    url, start_time, duration = *ARGV

    generator = GifGenerator.generate(
      :source_file => VideoDownloader.download(url).download_path,
      :start_time  => start_time,
      :duration    => duration
    )

    puts "Animated gif: #{generator.output_path}"
  end
}

require 'uri'

class CommandLineUtility
  class << self
    def path
      new.path
    end
  end

  def initialize
    install unless installed?
  end
end

class YoutubeDLCommandLineUtility < CommandLineUtility
  INSTALL_PATH = "/tmp/youtube-dl"
  INSTALL_URL  = 'https://raw.github.com/rg3/youtube-dl/2012.02.27/youtube-dl'

  def installed?
    File.exists?(INSTALL_PATH) || (%x|which youtube-dl| && $?.success?)
  end

  def path
    if File.exists?(INSTALL_PATH)
      INSTALL_PATH
    else
      %x|which youtube-dl|.chomp
    end
  end

  def install
    %x|curl '#{INSTALL_URL}' > #{INSTALL_PATH}|
    %x|chmod +x #{INSTALL_PATH}|
  end
end

class MplayerCommandLineUtility < CommandLineUtility
  INSTALL_URL   = 'http://mplayerosxext.googlecode.com/files/MPlayer-OSX-Extended_rev14.zip'
  DOWNLOAD_PATH = '/tmp/mplayer.zip'
  EXECUTABLE    = "/tmp/MPlayer OSX Extended.app/Contents/"   +
                  "Resources/Binaries/mpextended.mpBinaries/" +
                  "Contents/mpextended.mpBinaries/Contents/MacOS/mplayer"

  def installed?
    File.exists?(EXECUTABLE) || (%x|which mplayer| && $?.success?)
  end

  def path
    if File.exists?(EXECUTABLE)
      EXECUTABLE
    else
      %x|which mplayer|.chomp
    end
  end

  def install
    %x|curl '#{INSTALL_URL}' > #{DOWNLOAD_PATH}| unless File.exists?(DOWNLOAD_PATH)
    Dir.chdir('/tmp') do
      %x|unzip #{DOWNLOAD_PATH}|
    end
  end
end

class VideoDownloader
  DOWNLOAD_PATH = '/tmp'

  class << self
    def download(url)
      downloader = new(url)
      downloader.download
      downloader
    end
  end

  attr_reader :url
  def initialize(url)
    @url = URI.parse(url)
    ensure_url_is_valid
  end

  def id
    @id ||= query_string['v']
  end

  def download
    system("#{youtube_dl} -o #{download_path} '#{url}'")
  end

  def youtube_dl
    YoutubeDLCommandLineUtility.path
  end

  def download_path
    File.join(DOWNLOAD_PATH, target_file_name)
  end

  private
    def target_file_name
      "#{id}.flv"
    end

    def ensure_url_is_valid
      if id.nil?
        raise ArgumentError, "YouTube url '#{url}' doesn't include video identifier"
      end
    end

    def query_string
      @query_string ||= url.query.split('&').inject({}) do |params, param|
        key, value = param.split('=')
        params[key] = value
        params
      end
    end
end

class GifGenerator
  class << self
    def generate(configuration)
      generator = new(configuration)
      generator.generate
      generator
    end
  end

  attr_reader :source_file, :start_time, :duration
  def initialize(configuration)
    @source_file = configuration[:source_file]
    @start_time  = configuration[:start_time]
    @duration    = configuration[:duration]
  end

  def generate
    %x{'#{mplayer}' #{source_file} -nosound -vo gif89a:fps=#{FRAMES_PER_SECOND}:output=#{output_path} -vf scale=#{SCALE} -ss #{start_time} -endpos #{duration}}
  end

  def mplayer
    MplayerCommandLineUtility.path
  end

  def output_path
    File.basename(source_file, '.*') + '.gif'
  end

  def to_s
    output_path
  end
end