/* sbt -- Simple Build Tool
 * Copyright 2008, 2009 Mark Harrah
 */
package sbt
package classpath

import java.io.File
import java.net.{ URL, URLClassLoader }
import annotation.tailrec

/**
 * This is a starting point for defining a custom ClassLoader.  Override 'doLoadClass' to define
 * loading a class that has not yet been loaded.
 */
abstract class LoaderBase(urls: Seq[URL], parent: ClassLoader) extends URLClassLoader(urls.toArray, parent) {
  require(parent != null) // included because a null parent is legitimate in Java
  @throws(classOf[ClassNotFoundException])
  override final def loadClass(className: String, resolve: Boolean): Class[_] =
    {
      val loaded = findLoadedClass(className)
      val found =
        if (loaded == null)
          doLoadClass(className)
        else
          loaded

      if (resolve)
        resolveClass(found)
      found
    }
  /** Provides the implementation of finding a class that has not yet been loaded.*/
  protected def doLoadClass(className: String): Class[_]
  /** Provides access to the default implementation of 'loadClass'.*/
  protected final def defaultLoadClass(className: String): Class[_] = super.loadClass(className, false)
}

/** Searches self first before delegating to the parent.*/
final class SelfFirstLoader(classpath: Seq[URL], parent: ClassLoader) extends LoaderBase(classpath, parent) {
  @throws(classOf[ClassNotFoundException])
  override final def doLoadClass(className: String): Class[_] =
    {
      try { findClass(className) }
      catch { case _: ClassNotFoundException => defaultLoadClass(className) }
    }
}

/** Doesn't load any classes itself, but instead verifies that all classes loaded through `parent` either come from `root` or `classpath`.*/
final class ClasspathFilter(parent: ClassLoader, root: ClassLoader, classpath: Set[File]) extends ClassLoader(parent) {
  private[this] val directories: Seq[File] = classpath.toSeq.filter(_.isDirectory)
  override def loadClass(className: String, resolve: Boolean): Class[_] =
    {
      val c = super.loadClass(className, resolve)
      if (includeLoader(c.getClassLoader, root) || fromClasspath(c))
        c
      else
        throw new ClassNotFoundException(className)
    }
  private[this] def fromClasspath(c: Class[_]): Boolean =
    {
      val codeSource = c.getProtectionDomain.getCodeSource
      (codeSource eq null) ||
        onClasspath(codeSource.getLocation)
    }
  private[this] def onClasspath(src: URL): Boolean =
    (src eq null) || (
      IO.urlAsFile(src) match {
        case Some(f) => classpath(f) || directories.exists(dir => IO.relativize(dir, f).isDefined)
        case None    => false
      }
    )

  override def getResource(name: String): URL = {
    val u = super.getResource(name)
    if (onClasspath(u)) u else null
  }

  override def getResources(name: String): java.util.Enumeration[URL] =
    {
      import collection.convert.WrapAsScala.{ enumerationAsScalaIterator => asIt }
      import collection.convert.WrapAsJava.{ asJavaEnumeration => asEn }
      val us = super.getResources(name)
      if (us ne null) asEn(asIt(us).filter(onClasspath)) else null
    }

  @tailrec private[this] def includeLoader(c: ClassLoader, base: ClassLoader): Boolean =
    (base ne null) && (
      (c eq base) || includeLoader(c, base.getParent)
    )
}

/**
 * Delegates class loading to `parent` for all classes included by `filter`.  An attempt to load classes excluded by `filter`
 * results in a `ClassNotFoundException`.
 */
final class FilteredLoader(parent: ClassLoader, filter: ClassFilter) extends ClassLoader(parent) {
  require(parent != null) // included because a null parent is legitimate in Java
  def this(parent: ClassLoader, excludePackages: Iterable[String]) = this(parent, new ExcludePackagesFilter(excludePackages))

  @throws(classOf[ClassNotFoundException])
  override final def loadClass(className: String, resolve: Boolean): Class[_] =
    {
      if (filter.include(className))
        super.loadClass(className, resolve)
      else
        throw new ClassNotFoundException(className)
    }
}

/** Defines a filter on class names. */
trait ClassFilter {
  def include(className: String): Boolean
}
abstract class PackageFilter(packages: Iterable[String]) extends ClassFilter {
  require(packages.forall(_.endsWith(".")))
  protected final def matches(className: String): Boolean = packages.exists(className.startsWith)
}
/**
 * Excludes class names that begin with one of the packages in `exclude`.
 * Each package name in `packages` must end with a `.`
 */
final class ExcludePackagesFilter(exclude: Iterable[String]) extends PackageFilter(exclude) {
  def include(className: String): Boolean = !matches(className)
}

/**
 * Includes class names that begin with one of the packages in `include`.
 * Each package name in `include` must end with a `.`
 */
final class IncludePackagesFilter(include: Iterable[String]) extends PackageFilter(include) {
  def include(className: String): Boolean = matches(className)
}

/**
 * Configures a [[NativeCopyLoader]].
 * The loader will provide native libraries listed in `explicitLibraries` and on `searchPaths` by copying them to `tempDirectory`.
 * If `tempDirectory` is unique to the class loader, this ensures that the class loader gets a unique path for
 * the native library and avoids the restriction on a native library being loaded by a single class loader.
 */
final class NativeCopyConfig(val tempDirectory: File, val explicitLibraries: Seq[File], val searchPaths: Seq[File])

/**
 * Loads native libraries from a temporary location in order to work around the jvm native library uniqueness restriction.
 * See [[NativeCopyConfig]] for configuration details.
 */
trait NativeCopyLoader extends ClassLoader {
  /** Configures this loader.  See [[NativeCopyConfig]] for details. */
  protected val config: NativeCopyConfig
  import config._

  private[this] val mapped = new collection.mutable.HashMap[String, String]

  override protected def findLibrary(name: String): String =
    synchronized { mapped.getOrElseUpdate(name, findLibrary0(name)) }

  private[this] def findLibrary0(name: String): String =
    {
      val mappedName = System.mapLibraryName(name)
      val explicit = explicitLibraries.filter(_.getName == mappedName).toStream
      val search = searchPaths.toStream flatMap relativeLibrary(mappedName)
      (explicit ++ search).headOption.map(copy).orNull
    }
  private[this] def relativeLibrary(mappedName: String)(base: File): Seq[File] =
    {
      val f = new File(base, mappedName)
      if (f.isFile) f :: Nil else Nil
    }
  private[this] def copy(f: File): String =
    {
      val target = new File(tempDirectory, f.getName)
      IO.copyFile(f, target)
      target.getAbsolutePath
    }
}