package cbt
import java.io._
import java.nio.file.Files.readAllBytes
import java.net._
import org.eclipse.jgit.api._
import org.eclipse.jgit.internal.storage.file._
import org.eclipse.jgit.transport.UsernamePasswordCredentialsProvider
import org.eclipse.jgit.lib.Ref

object GitDependency{
  val GitUrl = "(git:|https:|file:/)//([^/]+)/(.+)".r
}
case class GitDependency(
  url: String, ref: String, subDirectory: Option[String] = None // example: git://github.com/cvogt/cbt.git#<some-hash>
)(implicit val logger: Logger, classLoaderCache: ClassLoaderCache, context: Context ) extends DependencyImplementation{
  import GitDependency._
  override def lib = new Lib(logger)
  def moduleKey = this.getClass.getName ++ "(" ++ url ++ subDirectory.map("/" ++ _).getOrElse("") ++ "#" ++ ref ++ ")"
  def transientCache = context.transientCache
  // TODO: add support for authentication via ssh and/or https
  // See http://www.codeaffine.com/2014/12/09/jgit-authentication/
  private val GitUrl( _, domain, path ) = url  

  private val credentialsFile = context.projectDirectory ++ "/git.login"

  private def authenticate(_git: CloneCommand) =
    if(!credentialsFile.exists){
      _git
    } else {
      val (user, password) = {
        // TODO: implement safer method than reading credentials from plain text file
        val c = new String(readAllBytes(credentialsFile.toPath)).split("\n").head.trim.split(":")
        (c(0), c.drop(1).mkString(":"))
      }
      _git.setCredentialsProvider( new UsernamePasswordCredentialsProvider(user, password) )
    }

  def checkout: File = taskCache[GitDependency]("checkout").memoize{
    val checkoutDirectory = context.cache ++ s"/git/$domain/$path/$ref"
    val _git = if(checkoutDirectory.exists){
      logger.git(s"Found existing checkout of $url#$ref in $checkoutDirectory")
      val _git = new Git(new FileRepository(checkoutDirectory ++ "/.git"))
      val actualRef = _git.getRepository.getBranch
      if(actualRef != ref){
        logger.git(s"actual ref '$actualRef' does not match expected ref '$ref' - fetching and checking out")
        _git.fetch().call()
        _git.checkout().setName(ref).call
      }
      _git
    } else {
      logger.git(s"Cloning $url into $checkoutDirectory")
      val _git = authenticate(
        Git
          .cloneRepository()
          .setURI(url)
          .setDirectory(checkoutDirectory)
      ).call()

      logger.git(s"Checking out ref $ref")
      _git.checkout().setName(ref).call()
      _git
    }
    val actualRef = _git.getRepository.getBranch
    assert( actualRef == ref, s"actual ref '$actualRef' does not match expected ref '$ref'")
    checkoutDirectory
  }
  def dependency = taskCache[GitDependency]("dependency").memoize{
    DirectoryDependency(
      context.copy(
        projectDirectory = checkout ++ subDirectory.map("/" ++ _).getOrElse("")
      )
    )
  }

  def dependencies = Seq(dependency)

  def exportedClasspath = ClassPath()
  private[cbt] def targetClasspath = exportedClasspath
  def needsUpdate: Boolean = false
}