slim-docker.sbt

import com.typesafe.sbt.packager.Keys.{daemonGroup, dockerCmd}
import com.typesafe.sbt.packager.docker.{Cmd, CmdLike, ExecCmd}

dockerCommands := {
  val dockerBaseDirectory = (defaultLinuxInstallLocation in Docker).value
  val relativeBaseDirectory = dockerBaseDirectory.drop(1)
  def relativeToBuild(file: String): String = relativeBaseDirectory + "/" + file

  val fileMappings = scriptClasspathOrdering.value.toMap.map { case (k, v) => (k.getName, v)}
  val projectArtifacts = projectDependencyArtifacts.value.map(f => fileMappings(f.data.getName))
  val libraryArtifacts = scriptClasspathOrdering.value.map(_._2).diff(projectArtifacts)

  val relativeLibArtifacts = libraryArtifacts.map(relativeToBuild).mkString(" ")
  val relativeProjectArtifacts = projectArtifacts.map(relativeToBuild).mkString(" ")

  val user = (daemonUser in Docker).value
  val group = (daemonGroup in Docker).value

  Seq(
    Cmd("FROM",     dockerBaseImage.value),
    Cmd("WORKDIR",  dockerBaseDirectory),
    Cmd("ADD",      s"$relativeLibArtifacts /opt/docker/lib/"),
    Cmd("ADD",      s"$relativeProjectArtifacts /opt/docker/lib/"),
    Cmd("ADD",      "opt/docker/bin /opt/docker/bin"),
    Cmd("EXPOSE", dockerExposedPorts.value mkString " ")
  ) ++
    makeVolumes(dockerExposedVolumes.value, user, group) ++ Seq(
    makeUser(user),
    makeEntrypoint(dockerEntrypoint.value),
    makeCmd(dockerCmd.value))
}

// These definitions had to be copied from com.typesafe.sbt.packager.docker.DockerPlugin due
// to private access.

def makeUser(daemonUser: String): CmdLike =
  Cmd("USER", daemonUser)

def makeEntrypoint(entrypoint: Seq[String]): CmdLike =
  ExecCmd("ENTRYPOINT", entrypoint: _*)

def makeCmd(args: Seq[String]): CmdLike =
  ExecCmd("CMD", args: _*)

def makeChown(daemonUser: String, daemonGroup: String, directories: Seq[String]): CmdLike =
  ExecCmd("RUN", Seq("chown", "-R", s"$daemonUser:$daemonGroup") ++ directories: _*)

def makeVolumes(exposedVolumes: Seq[String], daemonUser: String, daemonGroup: String): Seq[CmdLike] = {
  if (exposedVolumes.isEmpty) Seq.empty
  else Seq(
    ExecCmd("RUN", Seq("mkdir", "-p") ++ exposedVolumes: _*),
    makeChown(daemonUser, daemonGroup, exposedVolumes),
    ExecCmd("VOLUME", exposedVolumes: _*)
  )
}