require 'dotenv/load'
require 'json'
require 'open-uri'
require 'twitter'

Dotenv.load

TWITTER_CONSUMER_KEY = ENV["TWITTER_CONSUMER_KEY"]
TWITTER_CONSUMER_SECRET = ENV["TWITTER_CONSUMER_SECRET"]
TWITTER_ACCESS_TOKEN = ENV["TWITTER_ACCESS_TOKEN"]
TWITTER_ACCESS_TOKEN_SECRET = ENV["TWITTER_ACCESS_TOKEN_SECRET"]

YOUTUBE_DL_PATH = `which youtube-dl`.chomp
FFMPEG_PATH = `which ffmpeg`.chomp
FFPROBE_PATH = `which ffprobe`.chomp

VIDEO_PATH = "/tmp/video.mp4"
FRAME_PATH = "/tmp/frame.png"

PLAYLIST_ID = ENV["PLAYLIST_ID"]

throw "TWITTER_CONSUMER_KEY is required" unless TWITTER_CONSUMER_KEY
throw "TWITTER_CONSUMER_SECRET is required" unless TWITTER_CONSUMER_SECRET
throw "TWITTER_ACCESS_TOKEN is required" unless TWITTER_ACCESS_TOKEN
throw "TWITTER_ACCESS_TOKEN_SECRET is required" unless TWITTER_ACCESS_TOKEN_SECRET

throw "PLAYLIST_ID is required" unless PLAYLIST_ID

throw "Can't find youtube-dl" if YOUTUBE_DL_PATH.empty?
throw "Can't find ffprobe" if FFPROBE_PATH.empty?
throw "Can't find ffmpeg" if FFMPEG_PATH.empty?

class YouTubeService
  def initialize(playlist_id)
    @playlist_id = playlist_id
  end

  def fetch_random_frame_of_random_video
    download_random_video
    extract_frame
    delete_video
  end

  def download_random_video
    `#{YOUTUBE_DL_PATH} --playlist-random --max-downloads 1 -o #{VIDEO_PATH} -f mp4 #{@playlist_id}`
  end

  def extract_frame
    length = get_video_length
    random_second = rand(0..length)
    `#{FFMPEG_PATH} -v error -ss #{random_second} -i #{VIDEO_PATH} -frames 1 -y #{FRAME_PATH}`
  end

  def get_video_length
    `#{FFPROBE_PATH} -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 #{VIDEO_PATH}`.chomp.to_i
  end

  def delete_video
    `rm #{VIDEO_PATH}`
  end

  def delete_frame
    `rm #{FRAME_PATH}`
  end
end

class TwitterService
  def initialize(key, secret, token, token_secret)
    @twitter = Twitter::REST::Client.new do |config|
      config.consumer_key = key
      config.consumer_secret = secret
      config.access_token = token
      config.access_token_secret = token_secret
    end
  end

  def tweet_image(filepath)
    @twitter.update_with_media(String.new, File.new(filepath))
  end
end

youtube = YouTubeService.new(PLAYLIST_ID)
youtube.fetch_random_frame_of_random_video
twitter = TwitterService.new(
  TWITTER_CONSUMER_KEY,
  TWITTER_CONSUMER_SECRET,
  TWITTER_ACCESS_TOKEN,
  TWITTER_ACCESS_TOKEN_SECRET,
)
twitter.tweet_image(FRAME_PATH)
youtube.delete_frame