gistfile1.scala

/**
 * Creates a build properties file resource and packages it into the JAR,
 * which can be read for various information such as version and build time.
 * */
trait BuildPropertiesResource extends BasicScalaProject {
  /**
   * Specifies the name of the resource file. This is put [by default]
   * in the top level directory of the jar.
   * */
  def buildPropertiesResourceFile = "build.properties"

  /**
   * Specifies the actual path to the resource in the JAR.
   * */
  def buildPropertiesResourcePath = (outputPath ##) / buildPropertiesResourceFile

  /**
   * Specifies the properties which will actually go into the build
   * properties resource file.
   * */
  def buildPropertiesResourceData = Map("build.time" -> System.currentTimeMillis().toString,
                                        "build.version" -> version.toString)

  // Make the compile task depend on writing the resource
  override def compileAction = super.compileAction dependsOn(writeBuildPropertiesResource)

  // Add the build resource to the main resources list so that
  // it is properly packaged to the jar.
  abstract override def mainResources = super.mainResources +++ buildPropertiesResourcePath

  // The actual task to write out the build resource
  lazy val writeBuildPropertiesResource = writeBuildPropertiesResourceTask

  protected def writeBuildPropertiesResourceTask: Task = task {
    import java.io.FileOutputStream
    import java.util.Properties

    val props = new Properties()
    buildPropertiesResourceData.foreach(pair => props.setProperty(pair._1, pair._2))

    val outStream = new FileOutputStream(buildPropertiesResourcePath.asFile)
    props.store(outStream, "Build properties from compile-time")
    outStream.close()
    None
  }
}