import java.security.MessageDigest

class GenMD5 extends SourceTask {

  def outputDir

  @OutputDirectory
  File getOutputDir() { project.file(outputDir) }

  @TaskAction
  void writeMD5s() {

    source.each { file ->
      MessageDigest digest = MessageDigest.getInstance("MD5")

      digest.update(file.bytes)

      def checksum = new BigInteger(1, digest.digest()).toString(16).padLeft(32, "0")

      new File(outputDir, file.name + ".md5").text = checksum
    }
  }
}

project.GenMD5 = GenMD5.class