require 'pathname'
require 'digest/md5'

module Travis
  class Assets
    class Version
      FILE_NAME = 'public/version'
      SOURCES = %w(AssetFile Gemfile.lock assets)

      def self.update
        new.update
      end

      attr_reader :roots

      def initialize(roots = nil)
        @roots = roots
      end

      def read
        file.read
      end

      def update
        @hash = nil
        write(hash)
        hash
      end

      protected

        def cwd
          Pathname.new(File.expand_path('.'))
        end

        def file
          cwd.join(FILE_NAME)
        end

        def write(version)
          file.open('w+') { |f| f.write(version) }
        end

        def hash
          @hash ||= digest.to_s[0..7]
        end

        def digest
          Digest::MD5.new << `ls -lAR #{sources.join(' ')} | awk '{ print $5, $6, $7, $8, $9, $10 }'`
        end

        def sources
          roots.map do |root|
            SOURCES.map do |source|
              source = Pathname.new(root).join(source)
              source.to_s if source.exist?
            end
          end.flatten.compact
        end
    end
  end
end