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@|git://|https://|file:///)([^/:]+)[/:](.+)".r
  def apply(
    url: String, ref: String, subDirectory: Option[String] = None, // example: git://github.com/cvogt/cbt.git#<some-hash>
    subBuild: Option[String] = None
  )(implicit context: Context ): LazyDependency = withCheckoutDirectory(url, ref, subDirectory, subBuild)._2
  def withCheckoutDirectory(
    url: String, ref: String, subDirectory: Option[String] = None, // example: git://github.com/cvogt/cbt.git#<some-hash>
    subBuild: Option[String] = None
  )(implicit context: Context ): ( File, LazyDependency ) = {
    lazy val moduleKey = (
      this.getClass.getName
      ++ "(" ++ url ++ subDirectory.map("/" ++ _).getOrElse("") ++ "#" ++ ref
      ++ ", "
      ++ subBuild.mkString(", ")
      ++ ")"
    )

    val taskCache = new PerClassCache( context.transientCache, moduleKey )( context.logger )
    val c = taskCache[Dependency]("checkout").memoize{ checkout(url, ref) }
    val workingDirectory = subDirectory.map(c / _).getOrElse(c)
    c -> DirectoryDependency(
      context.copy(
        workingDirectory = workingDirectory,
        loop = false
      ),
      subBuild
    )
  }
  def checkout(url: String, ref: String)(implicit context: Context): File = {
    // TODO: add support for authentication via ssh and/or https
    // See http://www.codeaffine.com/2014/12/09/jgit-authentication/
    val credentialsFile = context.workingDirectory ++ "/git.login"
    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) )
      }

    val logger = context.logger
    val GitUrl( _, domain, path ) = url
    val checkoutDirectory = context.cache / s"git/$domain/${path.stripSuffix(".git")}/$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
  }
}