module Jekyll
  class MediaFilesGenerator < Generator
    safe true
    priority :high

    def generate(site)
      site.collections['podcasts'].docs.each do |document|
        date = document.data['date'].strftime('%Y-%m-%d')
        slug = document.data['slug']
        flac = "resources/podcasts/#{date}-#{slug}.flac"
        ogg =  "resources/podcasts/#{date}-#{slug}.ogg"

        unless File.exist? ogg then
          puts "Missing '#{ogg}' file, generating..."
          puts `ffmpeg -i #{flac} -ar 48000 -vn -c:a libvorbis -b:a 320k #{ogg}`
          site.static_files << Jekyll::StaticFile.new(site, site.source, '', ogg)
        end

        checksum_file = "#{ogg}.checksum"
        checksum = `sha256sum #{flac} #{ogg} | sha256sum | awk '{ print $1 }'`
        if File.exist? checksum_file then
          unless checksum == File.read(checksum_file)
            raise "Checksum mismatch for '#{flac}'.\nRe-generate the Ogg files and checksums with:\n\nrm '#{ogg}' '#{checksum_file}'"
          end
        else
          puts "Missing checksum for '#{flac}', generating..."
          File.write(checksum_file, checksum)
        end
      end
    end
  end
end