jif

#! /usr/bin/ruby

DEFAULT_FPS   = 8
DEFAULT_SCALE = 1280
MAX_FPS       = 60
PALETTE_TEMP  = '_palette.png'

USAGE_BANNER  = <<DOC
  Usage: jif <movie> [fps] [scale] [outfile]

    fps: Frame rate <= #{MAX_FPS} (default: #{DEFAULT_FPS})
  scale: Width of the resulting gif > #{MAX_FPS} (default: #{DEFAULT_SCALE})
outfile: Path to the output gif (default: <movie>.gif)
DOC

def explode(reason: nil)
  puts reason if reason
  puts
  puts USAGE_BANNER
  exit 1
end

def remove_extension(path)
  basename = File.basename(path, File.extname(path))
  dirname = File.dirname(path)
  File.join(dirname, basename)
end

def run_command(args)
  puts "\n#{args.join(' ')}\n\n"
  system(*args)
end

def main
  numeric_opts, file_names = ARGV.partition { |arg| arg =~ /^\d+$/ }

  # Parse numeric opts
  numeric_opts = numeric_opts.map(&:to_i)
  fps   = numeric_opts.select { |o| o <= MAX_FPS }.first || DEFAULT_FPS
  scale = numeric_opts.select { |o| o > MAX_FPS }.first || DEFAULT_SCALE

  # Parse file names
  explode(reason: 'Missing argument: you need a <movie>, duder!') if file_names.size == 0
  movie_in, movie_out = file_names
  movie_out = remove_extension(movie_in) + '.gif' if movie_out.nil?

  # Produce the palette
  run_command(%W(
    ffmpeg -y -i #{movie_in}
    -vf fps=#{fps},scale=#{scale}:-1:flags=lanczos,palettegen
    #{PALETTE_TEMP}
  ))

  # Encode
  run_command(%W(
    ffmpeg -y -i #{movie_in}
    -i #{PALETTE_TEMP}
    -filter_complex fps=#{fps},scale=#{scale}:-1:flags=lanczos[x];[x][1:v]paletteuse
    #{movie_out}
  ))

  # Clean up
  run_command(%W(rm #{PALETTE_TEMP}))

  # Display info and the gif
  run_command(%W(du -h #{movie_out}))

  run_command(%W(qlmanage -p #{movie_out}))
end

main