package sbt

import java.io.File
import java.net.URL
import Attributed.data
import Build.analyzed
import xsbt.api.{ Discovered, Discovery }

object PluginDiscovery {
  /**
   * Relative paths of resources that list top-level modules that are available.
   * Normally, the classes for those modules will be in the same classpath entry as the resource.
   */
  object Paths {
    final val AutoPlugins = "sbt/sbt.autoplugins"
    final val Plugins = "sbt/sbt.plugins"
    final val Builds = "sbt/sbt.builds"
  }
  /** Names of top-level modules that subclass sbt plugin-related classes: [[Plugin]], [[AutoPlugin]], and [[Build]]. */
  final class DiscoveredNames(val plugins: Seq[String], val autoPlugins: Seq[String], val builds: Seq[String])

  def emptyDiscoveredNames: DiscoveredNames = new DiscoveredNames(Nil, Nil, Nil)

  /** Discovers and loads the sbt-plugin-related top-level modules from the classpath and source analysis in `data` and using the provided class `loader`. */
  def discoverAll(data: PluginData, loader: ClassLoader): DetectedPlugins =
    {
      def discover[T](resource: String)(implicit classTag: reflect.ClassTag[T]) =
        binarySourceModules[T](data, loader, resource)
      import Paths._
      // TODO - Fix this once we can autodetect AutoPlugins defined by sbt itself.
      val defaultAutoPlugins = Seq(
        "sbt.plugins.IvyPlugin" -> sbt.plugins.IvyPlugin,
        "sbt.plugins.JvmPlugin" -> sbt.plugins.JvmPlugin,
        "sbt.plugins.CorePlugin" -> sbt.plugins.CorePlugin,
        "sbt.plugins.JUnitXmlReportPlugin" -> sbt.plugins.JUnitXmlReportPlugin
      )
      val detectedAutoPugins = discover[AutoPlugin](AutoPlugins)
      val allAutoPlugins = (defaultAutoPlugins ++ detectedAutoPugins.modules) map {
        case (name, value) =>
          DetectedAutoPlugin(name, value, sbt.Plugins.hasAutoImportGetter(value, loader))
      }
      new DetectedPlugins(discover[Plugin](Plugins), allAutoPlugins, discover[Build](Builds))
    }

  /** Discovers the sbt-plugin-related top-level modules from the provided source `analysis`. */
  def discoverSourceAll(analysis: inc.Analysis): DiscoveredNames =
    {
      def discover[T](implicit classTag: reflect.ClassTag[T]): Seq[String] =
        sourceModuleNames(analysis, classTag.runtimeClass.getName)
      new DiscoveredNames(discover[Plugin], discover[AutoPlugin], discover[Build])
    }

  // TODO: for 0.14.0, consider consolidating into a single file, which would make the classpath search 4x faster
  /** Writes discovered module `names` to zero or more files in `dir` as per [[writeDescriptor]] and returns the list of files written. */
  def writeDescriptors(names: DiscoveredNames, dir: File): Seq[File] =
    {
      import Paths._
      val files =
        writeDescriptor(names.plugins, dir, Plugins) ::
          writeDescriptor(names.autoPlugins, dir, AutoPlugins) ::
          writeDescriptor(names.builds, dir, Builds) ::
          Nil
      files.flatMap(_.toList)
    }

  /** Stores the module `names` in `dir / path`, one per line, unless `names` is empty and then the file is deleted and `None` returned. */
  def writeDescriptor(names: Seq[String], dir: File, path: String): Option[File] =
    {
      val descriptor: File = new File(dir, path)
      if (names.isEmpty) {
        IO.delete(descriptor)
        None
      } else {
        IO.writeLines(descriptor, names.distinct.sorted)
        Some(descriptor)
      }
    }

  /**
   * Discovers the names of top-level modules listed in resources named `resourceName` as per [[binaryModuleNames]] or
   * available as analyzed source and extending from any of `subclasses` as per [[sourceModuleNames]].
   */
  def binarySourceModuleNames(classpath: Seq[Attributed[File]], loader: ClassLoader, resourceName: String, subclasses: String*): Seq[String] =
    (
      binaryModuleNames(data(classpath), loader, resourceName) ++
      (analyzed(classpath) flatMap (a => sourceModuleNames(a, subclasses: _*)))
    ).distinct

  /** Discovers top-level modules in `analysis` that inherit from any of `subclasses`. */
  def sourceModuleNames(analysis: inc.Analysis, subclasses: String*): Seq[String] =
    {
      val subclassSet = subclasses.toSet
      val ds = Discovery(subclassSet, Set.empty)(Tests.allDefs(analysis))
      ds.flatMap {
        case (definition, Discovered(subs, _, _, true)) =>
          if ((subs & subclassSet).isEmpty) Nil else definition.name :: Nil
        case _ => Nil
      }
    }

  /**
   * Obtains the list of modules identified in all resource files `resourceName` from `loader` that are on `classpath`.
   * `classpath` and `loader` are both required to ensure that `loader`
   * doesn't bring in any resources outside of the intended `classpath`, such as from parent loaders.
   */
  def binaryModuleNames(classpath: Seq[File], loader: ClassLoader, resourceName: String): Seq[String] =
    {
      import collection.JavaConversions._
      loader.getResources(resourceName).toSeq.filter(onClasspath(classpath)) flatMap { u =>
        IO.readLinesURL(u).map(_.trim).filter(!_.isEmpty)
      }
    }

  /** Returns `true` if `url` is an entry in `classpath`.*/
  def onClasspath(classpath: Seq[File])(url: URL): Boolean =
    IO.urlAsFile(url) exists (classpath.contains _)

  private[sbt] def binarySourceModules[T](data: PluginData, loader: ClassLoader, resourceName: String)(implicit classTag: reflect.ClassTag[T]): DetectedModules[T] =
    {
      val classpath = data.classpath
      val namesAndValues = if (classpath.isEmpty) Nil else {
        val names = binarySourceModuleNames(classpath, loader, resourceName, classTag.runtimeClass.getName)
        loadModules[T](data, names, loader)
      }
      new DetectedModules(namesAndValues)
    }

  private[this] def loadModules[T: reflect.ClassTag](data: PluginData, names: Seq[String], loader: ClassLoader): Seq[(String, T)] =
    try ModuleUtilities.getCheckedObjects[T](names, loader)
    catch {
      case e: ExceptionInInitializerError =>
        val cause = e.getCause
        if (cause eq null) throw e else throw cause
      case e: LinkageError => incompatiblePlugins(data, e)
    }

  private[this] def incompatiblePlugins(data: PluginData, t: LinkageError): Nothing =
    {
      val evicted = data.report.toList.flatMap(_.configurations.flatMap(_.evicted))
      val evictedModules = evicted map { id => (id.organization, id.name) } distinct;
      val evictedStrings = evictedModules map { case (o, n) => o + ":" + n }
      val msgBase = "Binary incompatibility in plugins detected."
      val msgExtra = if (evictedStrings.isEmpty) "" else "\nNote that conflicts were resolved for some dependencies:\n\t" + evictedStrings.mkString("\n\t")
      throw new IncompatiblePluginsException(msgBase + msgExtra, t)
    }
}
