package scala
package tools
package reflect

import scala.tools.cmd.CommandLineParser
import scala.tools.nsc.reporters._
import scala.tools.nsc.CompilerCommand
import scala.tools.nsc.io.{AbstractFile, VirtualDirectory}
import scala.reflect.internal.util.AbstractFileClassLoader
import scala.reflect.internal.Flags._
import scala.reflect.internal.util.NoSourceFile
import java.lang.{Class => jClass}
import java.lang.System.{lineSeparator => EOL}
import scala.reflect.NameTransformer
import scala.reflect.api.JavaUniverse
import scala.reflect.io.NoAbstractFile
import scala.reflect.internal.FatalError

abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>

  val mirror: u.Mirror

  def mkToolBox(frontEnd: FrontEnd = mkSilentFrontEnd(), options: String = ""): ToolBox[U] =
    new ToolBoxImpl(frontEnd, options)

  private class ToolBoxImpl(val frontEnd: FrontEnd, val options: String) extends ToolBox[U] { toolBoxSelf =>

    val u: factorySelf.u.type = factorySelf.u

    lazy val classLoader = new AbstractFileClassLoader(virtualDirectory, factorySelf.mirror.classLoader)
    lazy val mirror: u.Mirror = u.runtimeMirror(classLoader)

    lazy val arguments = CommandLineParser.tokenize(options)
    lazy val virtualDirectory =
      arguments.iterator.sliding(2).collectFirst{ case Seq("-d", dir) => dir } match {
        case Some(outDir) => AbstractFile.getDirectory(outDir)
        case None => new VirtualDirectory("(memory)", None)
      }

    class ToolBoxGlobal(settings: scala.tools.nsc.Settings, reporter0: Reporter)
    extends ReflectGlobal(settings, reporter0, toolBoxSelf.classLoader) {
      import definitions._

      private val trace = scala.tools.nsc.util.trace when settings.debug.value

      private var wrapCount = 0

      private final val wrapperMethodName = "wrapper"

      private def nextWrapperModuleName() = {
        wrapCount += 1
        // we need to use UUIDs here, because our toolbox might be spawned by another toolbox
        // that already has, say, __wrapper$1 in its virtual directory, which will shadow our codegen
        newTermName("__wrapper$" + wrapCount + "$" + java.util.UUID.randomUUID.toString.replace("-", ""))
      }

      // should be called after every use of ToolBoxGlobal in order to prevent leaks
      def cleanupCaches(): Unit = {
        perRunCaches.clearAll()
        undoLog.clear()
        analyzer.lastTreeToTyper = EmptyTree
        lastSeenSourceFile = NoSourceFile
        lastSeenContext = null
      }

      def verify(expr: Tree): Tree = {
        // Previously toolboxes used to typecheck their inputs before compiling.
        // Actually, the initial demo by Martin first typechecked the reified tree,
        // then ran it, which typechecked it again, and only then launched the
        // reflective compiler.
        //
        // However, as observed in https://github.com/scala/bug/issues/5464
        // current implementation typechecking is not always idempotent.
        // That's why we cannot allow inputs of toolboxes to be typechecked,
        // at least not until the aforementioned issue is closed.
        val typed = expr filter (t => t.tpe != null && t.tpe != NoType && !t.isInstanceOf[TypeTree])
        if (!typed.isEmpty) throw ToolBoxError("reflective toolbox has failed: cannot operate on trees that are already typed")

        if (expr.freeTypes.nonEmpty) {
          val ft_s = expr.freeTypes map (ft => s"  ${ft.name} ${ft.origin}") mkString "\n  "
          throw ToolBoxError(s"""
            |reflective toolbox failed due to unresolved free type variables:
            |$ft_s
            |have you forgotten to use TypeTag annotations for type parameters external to a reifee?
            |if you have troubles tracking free type variables, consider using -Xlog-free-types
            """.stripMargin.trim)
        }

        expr
      }

      def extractFreeTerms(expr0: Tree, wrapFreeTermRefs: Boolean): (Tree, scala.collection.mutable.LinkedHashMap[FreeTermSymbol, TermName]) = {
        val freeTerms = expr0.freeTerms
        val freeTermNames = scala.collection.mutable.LinkedHashMap[FreeTermSymbol, TermName]()
        freeTerms foreach (ft => {
          var name = ft.name.toString
          val namesakes = freeTerms takeWhile (_ != ft) filter (ft2 => ft != ft2 && ft.name == ft2.name)
          if (namesakes.length > 0) name += ("$" + (namesakes.length + 1))
          freeTermNames += (ft -> newTermName(name + nme.REIFY_FREE_VALUE_SUFFIX))
        })
        val expr = new Transformer {
          override def transform(tree: Tree): Tree =
            if (tree.hasSymbolField && tree.symbol.isFreeTerm) {
              tree match {
                case Ident(_) =>
                  val freeTermRef = Ident(freeTermNames(tree.symbol.asFreeTerm))
                  if (wrapFreeTermRefs) Apply(freeTermRef, List()) else freeTermRef
                case _ =>
                  throw new Error("internal error: %s (%s, %s) is not supported".format(tree, tree.productPrefix, tree.getClass))
              }
            } else {
              super.transform(tree)
            }
        }.transform(expr0)
        (expr, freeTermNames)
      }

      def transformDuringTyper(expr: Tree, mode: scala.reflect.internal.Mode, withImplicitViewsDisabled: Boolean, withMacrosDisabled: Boolean)(transform: (analyzer.Typer, Tree) => Tree): Tree = {
        def withWrapping(tree: Tree)(op: Tree => Tree) = if (mode == TERMmode) wrappingIntoTerm(tree)(op) else op(tree)
        withWrapping(verify(expr)) { expr =>
          // need to extract free terms, because otherwise you won't be able to typecheck macros against something that contains them
          val (extracted, freeTerms) = extractFreeTerms(expr, wrapFreeTermRefs = false)
          val exprBound = {
            val binders = freeTerms.toList.map { case (freeTerm, name) =>
              ValDef(NoMods, name, TypeTree(freeTerm.info), Select(Ident(PredefModule), newTermName("$qmark$qmark$qmark")))
            }
            Block(binders, extracted)
          }

          // !!! Why is this is in the empty package? If it's only to make
          // it inaccessible then please put it somewhere designed for that
          // rather than polluting the empty package with synthetics.
          // [Eugene] how can we implement that?
          val ownerClass       = rootMirror.EmptyPackageClass.newClassSymbol(newTypeName("<expression-owner>"))
          build.setInfo(ownerClass, ClassInfoType(List(ObjectTpe), newScope, ownerClass))
          val owner            = ownerClass.newLocalDummy(exprBound.pos)
          val currentTyper     = analyzer.newTyper(analyzer.rootContext(NoCompilationUnit, EmptyTree).make(exprBound, owner))
          import currentTyper.{context => currCtx}

          val run = new Run
          run.symSource(ownerClass) = NoAbstractFile // need to set file to something different from null, so that currentRun.defines works
          phase = run.typerPhase // need to set a phase to something <= typerPhase, otherwise implicits in typedSelect will be disabled
          globalPhase = run.typerPhase // amazing... looks like phase and globalPhase are different things, so we need to set them separately
          currCtx.initRootContext() // need to manually set context mode, otherwise typer.silent will throw exceptions
          reporter.reset()

          val (binders, transformed) =
            currCtx.withImplicits(enabled = !withImplicitViewsDisabled) {
              currCtx.withMacros(enabled = !withMacrosDisabled) {
                transform(currentTyper, exprBound)
              }
            } match {
              case Block(binders, transformed) => (binders, transformed)
              case transformed                 => (Nil, transformed)
            }

          val invertedIndex = freeTerms map (_.swap)
          val indexed = new Transformer {
            override def transform(tree: Tree): Tree =
              tree match {
                case Ident(name: TermName) if invertedIndex contains name =>
                  Ident(invertedIndex(name)) setType tree.tpe
                case _ =>
                  super.transform(tree)
              }
          }.transform(transformed)
          new TreeTypeSubstituter(binders map (_.symbol), binders map (b => SingleType(NoPrefix, invertedIndex(b.symbol.name.toTermName)))).traverse(indexed)
          indexed
        }
      }

      def typecheck(expr: Tree, pt: Type, mode: scala.reflect.internal.Mode, silent: Boolean, withImplicitViewsDisabled: Boolean, withMacrosDisabled: Boolean): Tree =
        transformDuringTyper(expr, mode, withImplicitViewsDisabled = withImplicitViewsDisabled, withMacrosDisabled = withMacrosDisabled)(
          (currentTyper, expr) => {
            trace("typing (implicit views = %s, macros = %s): ".format(!withImplicitViewsDisabled, !withMacrosDisabled))(showAttributed(expr, true, true, settings.Yshowsymowners.value, settings.Yshowsymkinds.value))
            currentTyper.silent(_.typed(expr, mode, pt), reportAmbiguousErrors = false) match {
              case analyzer.SilentResultValue(result) =>
                trace("success: ")(showAttributed(result, true, true, settings.Yshowsymkinds.value))
                result
              case error @ analyzer.SilentTypeError(_) =>
                trace("failed: ")(error.err.errMsg)
                if (!silent) throw ToolBoxError("reflective typecheck has failed: %s".format(error.err.errMsg))
                EmptyTree
            }
          })

      def inferImplicit(tree: Tree, pt: Type, isView: Boolean, silent: Boolean, withMacrosDisabled: Boolean, pos: Position): Tree =
        transformDuringTyper(tree, TERMmode, withImplicitViewsDisabled = false, withMacrosDisabled = withMacrosDisabled)(
          (currentTyper, tree) => {
            trace("inferring implicit %s (macros = %s): ".format(if (isView) "view" else "value", !withMacrosDisabled))(showAttributed(pt, true, true, settings.Yshowsymowners.value, settings.Yshowsymkinds.value))
            analyzer.inferImplicit(tree, pt, isView, currentTyper.context, silent, withMacrosDisabled, pos, (pos, msg) => throw ToolBoxError(msg))
          })

      private def wrapInPackageAndCompile(packageName: TermName, tree: ImplDef): Symbol = {
        val pdef = PackageDef(Ident(packageName), List(tree))
        val unit = new CompilationUnit(NoSourceFile)
        unit.body = pdef

        val run = new Run
        reporter.reset()
        run.compileUnits(List(unit), run.namerPhase)
        throwIfErrors()

        tree.symbol
      }

      def compile(expr0: Tree): () => Any = {
        val expr = build.SyntacticBlock(expr0 :: Nil)

        val freeTerms = expr.freeTerms // need to calculate them here, because later on they will be erased
        val thunks = freeTerms map (fte => () => fte.value) // need to be lazy in order not to distort evaluation order
        verify(expr)

        def wrapInModule(expr0: Tree): ModuleDef = {
          val (expr, freeTerms) = extractFreeTerms(expr0, wrapFreeTermRefs = true)

          val (obj, _) = rootMirror.EmptyPackageClass.newModuleAndClassSymbol(
            nextWrapperModuleName(), NoPosition, NoFlags)

          val minfo = ClassInfoType(List(ObjectTpe), newScope, obj.moduleClass)
          obj.moduleClass setInfo minfo
          obj setInfo obj.moduleClass.tpe

          val meth = obj.moduleClass.newMethod(newTermName(wrapperMethodName))
          def makeParam(schema: (FreeTermSymbol, TermName)) = {
            // see a detailed explanation of the STABLE trick in `GenSymbols.reifyFreeTerm`
            val (fv, name) = schema
            meth.newValueParameter(name, newFlags = if (fv.hasStableFlag) STABLE else 0) setInfo appliedType(definitions.FunctionClass(0).tpe, List(fv.tpe.resultType))
          }
          meth setInfo MethodType(freeTerms.map(makeParam).toList, AnyTpe)
          minfo.decls enter meth
          def defOwner(tree: Tree): Symbol = tree find (_.isDef) map (_.symbol) match {
            case Some(sym) if sym != null && sym != NoSymbol => sym.owner
            case _ => NoSymbol
          }
          trace("wrapping ")(defOwner(expr) -> meth)
          val methdef = DefDef(meth, expr changeOwner (defOwner(expr) -> meth))

          val moduledef = ModuleDef(
              obj,
              gen.mkTemplate(
                  List(TypeTree(ObjectTpe)),
                  noSelfType,
                  NoMods,
                  List(),
                  List(methdef),
                  NoPosition))
          trace("wrapped: ")(showAttributed(moduledef, true, true, settings.Yshowsymowners.value, settings.Yshowsymkinds.value))

          val cleanedUp = resetAttrs(moduledef)
          trace("cleaned up: ")(showAttributed(cleanedUp, true, true, settings.Yshowsymowners.value, settings.Yshowsymkinds.value))
          cleanedUp.asInstanceOf[ModuleDef]
        }

        val mdef = wrapInModule(expr)
        val msym = wrapInPackageAndCompile(mdef.name, mdef)

        val className = msym.fullName
        if (settings.debug) println("generated: "+className)
        def moduleFileName(className: String) = className + "$"
        val jclazz = jClass.forName(moduleFileName(className), true, classLoader)
        val jmeth = jclazz.getDeclaredMethods.find(_.getName == wrapperMethodName).get
        val jfield = jclazz.getDeclaredFields.find(_.getName == NameTransformer.MODULE_INSTANCE_NAME).get
        val singleton = jfield.get(null)

        // @odersky writes: Not sure we will be able to drop this. I forgot the reason why we dereference () functions,
        // but there must have been one. So I propose to leave old version in comments to be resurrected if the problem resurfaces.
        // @Eugene writes: this dates back to the days when one could only reify functions
        // hence, blocks were translated into nullary functions, so
        // presumably, it was useful to immediately evaluate them to get the result of a block
        // @Eugene writes: anyways, I'll stash the old sources here in comments in case anyone wants to revive them
        // val result = jmeth.invoke(singleton, freeTerms map (sym => sym.asInstanceOf[FreeTermVar].value.asInstanceOf[AnyRef]): _*)
        // if (etpe.typeSymbol != FunctionClass(0)) result
        // else {
        //   val applyMeth = result.getClass.getMethod("apply")
        //   applyMeth.invoke(result)
        // }
        () => {
          val result = jmeth.invoke(singleton, thunks map (_.asInstanceOf[AnyRef]): _*)
          if (jmeth.getReturnType == java.lang.Void.TYPE) ()
          else result
        }
      }

      def define(tree: ImplDef): Symbol = {
        val freeTerms = tree.freeTerms
        if (freeTerms.nonEmpty) throw ToolBoxError(s"reflective toolbox has failed: cannot have free terms in a top-level definition")
        verify(tree)
        wrapInPackageAndCompile(nextWrapperModuleName(), tree)
      }

      def parse(code: String): Tree = {
        reporter.reset()
        val tree = gen.mkTreeOrBlock(newUnitParser(code, "<toolbox>").parseStatsOrPackages())
        throwIfErrors()
        tree
      }

      def showAttributed(artifact: Any, printTypes: Boolean = true, printIds: Boolean = true, printOwners: Boolean = false, printKinds: Boolean = false): String = {
        val saved1 = settings.printtypes.value
        val saved2 = settings.uniqid.value
        val saved3 = settings.Yshowsymowners.value
        val saved4 = settings.Yshowsymkinds.value
        try {
          settings.printtypes.value = printTypes
          settings.uniqid.value = printIds
          settings.Yshowsymowners.value = printOwners
          settings.Yshowsymkinds.value = printKinds
          artifact.toString
        } finally {
          settings.printtypes.value = saved1
          settings.uniqid.value = saved2
          settings.Yshowsymowners.value = saved3
          settings.Yshowsymkinds.value = saved4
        }
      }

      // reporter doesn't accumulate errors, but the front-end does
      def throwIfErrors() = {
        if (frontEnd.hasErrors) throw ToolBoxError(
          "reflective compilation has failed:" + EOL + EOL + (frontEnd.infos map (_.msg) mkString EOL)
        )
      }
    }

    trait CompilerApi {
      val compiler: ToolBoxGlobal
      val importer: compiler.Importer { val from: u.type }
      val exporter: u.Importer { val from: compiler.type }
    }

    object withCompilerApi {
      private object api extends CompilerApi {
        lazy val compiler: ToolBoxGlobal = {
          try {
            val errorFn: String => Unit = msg => frontEnd.log(scala.reflect.internal.util.NoPosition, msg, frontEnd.ERROR)
            val command = new CompilerCommand(arguments.toList, errorFn)
            command.settings.outputDirs setSingleOutput virtualDirectory
            val instance = new ToolBoxGlobal(command.settings, frontEndToReporter(frontEnd, command.settings))
            if (frontEnd.hasErrors) {
              throw ToolBoxError(
                "reflective compilation has failed: cannot initialize the compiler:" + EOL + EOL +
                (frontEnd.infos map (_.msg) mkString EOL)
              )
            }
            instance
          } catch {
            case ex: Throwable =>
              throw ToolBoxError(s"reflective compilation has failed: cannot initialize the compiler due to $ex", ex)
          }
        }

        lazy val importer = compiler.mkImporter(u)
        lazy val exporter = importer.reverse
      }

      private val toolBoxLock = new Object
      def apply[T](f: CompilerApi => T): T = toolBoxLock.synchronized {
        try f(api)
        catch { case ex: FatalError => throw ToolBoxError(s"fatal compiler error", ex) }
        finally api.compiler.cleanupCaches()
      }
    }

    type TypecheckMode = scala.reflect.internal.Mode
    val TypecheckMode = scala.reflect.internal.Mode
    val TERMmode = TypecheckMode.EXPRmode
    val TYPEmode = TypecheckMode.TYPEmode | TypecheckMode.FUNmode
    val PATTERNmode = TypecheckMode.PATTERNmode

    def typecheck(tree: u.Tree, mode: TypecheckMode = TERMmode, expectedType: u.Type, silent: Boolean = false, withImplicitViewsDisabled: Boolean = false, withMacrosDisabled: Boolean = false): u.Tree = withCompilerApi { compilerApi =>
      import compilerApi._

      if (compiler.settings.verbose) println("importing "+tree+", expectedType = "+expectedType)
      val ctree: compiler.Tree = importer.importTree(tree)
      val cexpectedType: compiler.Type = importer.importType(expectedType)

      if (compiler.settings.verbose) println("typing "+ctree+", expectedType = "+expectedType)
      val ttree: compiler.Tree = compiler.typecheck(ctree, cexpectedType, mode, silent = silent, withImplicitViewsDisabled = withImplicitViewsDisabled, withMacrosDisabled = withMacrosDisabled)
      val uttree = exporter.importTree(ttree)
      uttree
    }

    def inferImplicitValue(pt: u.Type, silent: Boolean = true, withMacrosDisabled: Boolean = false, pos: u.Position = u.NoPosition): u.Tree = {
      inferImplicit(u.EmptyTree, pt, isView = false, silent = silent, withMacrosDisabled = withMacrosDisabled, pos = pos)
    }

    def inferImplicitView(tree: u.Tree, from: u.Type, to: u.Type, silent: Boolean = true, withMacrosDisabled: Boolean = false, pos: u.Position = u.NoPosition): u.Tree = {
      val functionTypeCtor = u.definitions.FunctionClass(1).asClass.toTypeConstructor
      val viewTpe = u.appliedType(functionTypeCtor, List(from, to))
      inferImplicit(tree, viewTpe, isView = true, silent = silent, withMacrosDisabled = withMacrosDisabled, pos = pos)
    }

    private def inferImplicit(tree: u.Tree, pt: u.Type, isView: Boolean, silent: Boolean, withMacrosDisabled: Boolean, pos: u.Position): u.Tree = withCompilerApi { compilerApi =>
      import compilerApi._

      if (compiler.settings.verbose) println(s"importing pt=$pt, tree=$tree, pos=$pos")
      val ctree: compiler.Tree = importer.importTree(tree)
      val cpt: compiler.Type = importer.importType(pt)
      val cpos: compiler.Position = importer.importPosition(pos)

      if (compiler.settings.verbose) println("inferring implicit %s of type %s, macros = %s".format(if (isView) "view" else "value", pt, !withMacrosDisabled))
      val itree: compiler.Tree = compiler.inferImplicit(ctree, cpt, isView = isView, silent = silent, withMacrosDisabled = withMacrosDisabled, pos = cpos)
      val uitree = exporter.importTree(itree)
      uitree
    }

    def resetLocalAttrs(tree: u.Tree): u.Tree = withCompilerApi { compilerApi =>
      import compilerApi._
      val ctree: compiler.Tree = importer.importTree(tree)
      val ttree: compiler.Tree = compiler.resetAttrs(ctree)
      val uttree = exporter.importTree(ttree)
      uttree
    }

    def untypecheck(tree: u.Tree): u.Tree = resetLocalAttrs(tree)

    def parse(code: String): u.Tree = withCompilerApi { compilerApi =>
      import compilerApi._
      if (compiler.settings.verbose) println("parsing "+code)
      val ctree: compiler.Tree = compiler.parse(code)
      val utree = exporter.importTree(ctree)
      utree
    }

    def compile(tree: u.Tree): () => Any = withCompilerApi { compilerApi =>
      import compilerApi._

      if (compiler.settings.verbose) println("importing "+tree)
      val ctree: compiler.Tree = importer.importTree(tree)

      if (compiler.settings.verbose) println("compiling "+ctree)
      compiler.compile(ctree)
    }

    def define(tree: u.ImplDef): u.Symbol = withCompilerApi { compilerApi =>
      import compilerApi._

      if (compiler.settings.verbose) println("importing "+tree)
      val ctree: compiler.ImplDef = importer.importTree(tree).asInstanceOf[compiler.ImplDef]

      if (compiler.settings.verbose) println("defining "+ctree)
      val csym: compiler.Symbol = compiler.define(ctree)
      val usym = exporter.importSymbol(csym)
      usym
    }

    def eval(tree: u.Tree): Any = compile(tree)()
  }
}
