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/*
 * Scala (https://www.scala-lang.org)
 *
 * Copyright EPFL and Lightbend, Inc.
 *
 * Licensed under Apache License 2.0
 * (http://www.apache.org/licenses/LICENSE-2.0).
 *
 * See the NOTICE file distributed with this work for
 * additional information regarding copyright ownership.
 */

package scala.tools.nsc
package backend.jvm
package opt

import scala.collection.concurrent.TrieMap
import scala.collection.immutable.IntMap
import scala.collection.{concurrent, mutable}
import scala.jdk.CollectionConverters._
import scala.reflect.internal.util.{NoPosition, Position}
import scala.tools.asm.tree._
import scala.tools.asm.{Opcodes, Type}
import scala.tools.nsc.backend.jvm.BTypes.InternalName
import scala.tools.nsc.backend.jvm.BackendReporting._
import scala.tools.nsc.backend.jvm.analysis.BackendUtils.LambdaMetaFactoryCall
import scala.tools.nsc.backend.jvm.analysis.TypeFlowInterpreter.{LMFValue, ParamValue}
import scala.tools.nsc.backend.jvm.analysis._
import scala.tools.nsc.backend.jvm.opt.BytecodeUtils._

abstract class CallGraph {
  val postProcessor: PostProcessor

  import postProcessor._
  import bTypes._
  import bTypesFromClassfile._
  import frontendAccess.recordPerRunCache

  /**
   * The call graph contains the callsites in the program being compiled.
   *
   * Indexing the call graph by the containing MethodNode and the invocation MethodInsnNode allows
   * finding callsites efficiently. For example, an inlining heuristic might want to know all
   * callsites within a callee method.
   *
   * Note that the call graph is not guaranteed to be complete: callsites may be missing. In
   * particular, if a method is very large, all of its callsites might not be in the hash map.
   * The reason is that adding a method to the call graph requires running an ASM analyzer, which
   * can be too slow.
   *
   * Note that call graph entries (Callsite instances) keep a reference to the invocation
   * MethodInsnNode, which keeps all AbstractInsnNodes of the method reachable. Adding classes
   * from the classpath to the call graph (in addition to classes being compiled) may prevent
   * method instruction nodes from being GCd. The ByteCodeRepository has a fixed size cache for
   * parsed ClassNodes - keeping all ClassNodes alive consumed too much memory.
   * The call graph is less problematic because only methods being called are kept alive, not entire
   * classes. But we should keep an eye on this.
   */
  val callsites: mutable.Map[MethodNode, Map[MethodInsnNode, Callsite]] = recordPerRunCache(concurrent.TrieMap.empty withDefaultValue Map.empty)

  /**
   * Closure instantiations in the program being compiled.
   *
   * Indexing closure instantiations by the containing MethodNode is beneficial for the closure
   * optimizer: finding callsites to re-write requires running a producers-consumers analysis on
   * the method. Here the closure instantiations are already grouped by method.
   */
   //currently single threaded access only
  val closureInstantiations: mutable.Map[MethodNode, Map[InvokeDynamicInsnNode, ClosureInstantiation]] = recordPerRunCache(concurrent.TrieMap.empty withDefaultValue Map.empty)

  /**
   * Store the position of every MethodInsnNode during code generation. This allows each callsite
   * in the call graph to remember its source position, which is required for inliner warnings.
   */
  val callsitePositions: concurrent.Map[MethodInsnNode, Position] = recordPerRunCache(TrieMap.empty)

  /**
   * Stores callsite instructions of invocations annotated `f(): @inline/noinline`.
   * Instructions are added during code generation (BCodeBodyBuilder). The maps are then queried
   * when building the CallGraph, every Callsite object has an annotated(No)Inline field.
   */
  //currently single threaded access only
  val inlineAnnotatedCallsites: mutable.Set[MethodInsnNode] = recordPerRunCache(mutable.Set.empty)
  //currently single threaded access only
  val noInlineAnnotatedCallsites: mutable.Set[MethodInsnNode] = recordPerRunCache(mutable.Set.empty)

  // Contains `INVOKESPECIAL` instructions that were cloned by the inliner and need to be resolved
  // statically by the call graph. See Inliner.maybeInlinedLater.
  val staticallyResolvedInvokespecial: mutable.Set[MethodInsnNode] = recordPerRunCache(mutable.Set.empty)

  def isStaticCallsite(call: MethodInsnNode): Boolean = {
    val opc = call.getOpcode
    opc == Opcodes.INVOKESTATIC || opc == Opcodes.INVOKESPECIAL && staticallyResolvedInvokespecial(call)
  }

  def removeCallsite(invocation: MethodInsnNode, methodNode: MethodNode): Option[Callsite] = {
    val methodCallsites = callsites(methodNode)
    val newCallsites = methodCallsites - invocation
    if (newCallsites.isEmpty) callsites.remove(methodNode)
    else callsites(methodNode) = newCallsites
    methodCallsites.get(invocation)
  }

  def addCallsite(callsite: Callsite): Unit = {
    val methodCallsites = callsites(callsite.callsiteMethod)
    callsites(callsite.callsiteMethod) = methodCallsites + (callsite.callsiteInstruction -> callsite)
  }

  def containsCallsite(callsite: Callsite): Boolean = callsites(callsite.callsiteMethod) contains callsite.callsiteInstruction

  def removeClosureInstantiation(indy: InvokeDynamicInsnNode, methodNode: MethodNode): Option[ClosureInstantiation] = {
    val methodClosureInits = closureInstantiations(methodNode)
    val newClosureInits = methodClosureInits - indy
    if (newClosureInits.isEmpty) closureInstantiations.remove(methodNode)
    else closureInstantiations(methodNode) = newClosureInits
    methodClosureInits.get(indy)
  }

  def addClass(classNode: ClassNode): Unit = {
    val classType = classBTypeFromClassNode(classNode)
    classNode.methods.asScala.foreach(addMethod(_, classType))
  }

  def refresh(methodNode: MethodNode, definingClass: ClassBType): Unit = {
    callsites.remove(methodNode)
    closureInstantiations.remove(methodNode)
    // callsitePositions, inlineAnnotatedCallsites, noInlineAnnotatedCallsites, staticallyResolvedInvokespecial
    // are left unchanged. They contain individual instructions, the state for those remains valid in case
    // the inliner performs a rollback.
    addMethod(methodNode, definingClass)
  }

  def addMethod(methodNode: MethodNode, definingClass: ClassBType): Unit = {
    if (!BytecodeUtils.isAbstractMethod(methodNode) && !BytecodeUtils.isNativeMethod(methodNode) && AsmAnalyzer.sizeOKForBasicValue(methodNode)) {
      lazy val typeAnalyzer = new NonLubbingTypeFlowAnalyzer(methodNode, definingClass.internalName)

      var methodCallsites = Map.empty[MethodInsnNode, Callsite]
      var methodClosureInstantiations = Map.empty[InvokeDynamicInsnNode, ClosureInstantiation]

      methodNode.instructions.iterator.asScala foreach {
        case call: MethodInsnNode if typeAnalyzer.frameAt(call) != null => // skips over unreachable code
          // JVMS 6.5 invokespecial: " If all of the following are true, let C be the direct superclass of the current class"
          def isSuperCall: Boolean =
            call.getOpcode == Opcodes.INVOKESPECIAL &&
              call.name != GenBCode.INSTANCE_CONSTRUCTOR_NAME && {
                val owner = call.owner
                definingClass.internalName != owner && {
                  var nextSuper = definingClass.info.get.superClass
                  while (nextSuper.nonEmpty) {
                    if (nextSuper.get.internalName == owner) return true
                    nextSuper = nextSuper.get.info.get.superClass
                  }
                  false
                }
              }
          val paramTps = FLazy(Type.getArgumentTypes(call.desc))
          // This is the type where method lookup starts (implemented in byteCodeRepository.methodNode)
          val preciseOwner =
            if (isStaticCallsite(call)) call.owner
            else if (isSuperCall) definingClass.info.get.superClass.get.internalName
            else if (call.getOpcode == Opcodes.INVOKESPECIAL) call.owner
            else {
              // invokevirtual, invokeinterface: start search at the type of the receiver
              val f = typeAnalyzer.frameAt(call)
              // Not Type.getArgumentsAndReturnSizes: in asm.Frame, size-2 values use a single stack slot
              val numParams = paramTps.get.length
              f.peekStack(numParams).getType.getInternalName
            }

          val callee: Either[OptimizerWarning, Callee] = {
            for {
              (method, declarationClass) <- byteCodeRepository.methodNode(preciseOwner, call.name, call.desc): Either[OptimizerWarning, (MethodNode, InternalName)]
              (declarationClassNode, calleeSourceFilePath) <- byteCodeRepository.classNodeAndSourceFilePath(declarationClass): Either[OptimizerWarning, (ClassNode, Option[String])]
            } yield {
              val declarationClassBType = classBTypeFromClassNode(declarationClassNode)
              val info = analyzeCallsite(method, declarationClassBType, call, paramTps, calleeSourceFilePath, definingClass)
              import info._
              Callee(
                callee = method,
                calleeDeclarationClass = declarationClassBType,
                isStaticallyResolved = isStaticallyResolved,
                sourceFilePath = sourceFilePath,
                annotatedInline = annotatedInline,
                annotatedNoInline = annotatedNoInline,
                samParamTypes = info.samParamTypes,
                calleeInfoWarning = warning)
            }
          }

          val argInfos = computeArgInfos(callee, call, paramTps, typeAnalyzer)

          // A nullness analysis could be used to prevent emitting unnecessary receiver null checks
          // when inlining non-static callsites. However, LocalOpt's nullness cleanup will also do
          // it after the fact, so we can avoid running the nullness analysis when building the call
          // graph (or when inlining).
          val receiverNotNull = call.getOpcode == Opcodes.INVOKESTATIC

          methodCallsites += call -> Callsite(
            callsiteInstruction = call,
            callsiteMethod = methodNode,
            callsiteClass = definingClass,
            callee = callee,
            argInfos = argInfos,
            callsiteStackHeight = typeAnalyzer.frameAt(call).getStackSize,
            receiverKnownNotNull = receiverNotNull,
            callsitePosition = callsitePositions.getOrElse(call, NoPosition),
            annotatedInline = inlineAnnotatedCallsites(call),
            annotatedNoInline = noInlineAnnotatedCallsites(call)
          )

        case LambdaMetaFactoryCall(indy, samMethodType, implMethod, instantiatedMethodType, indyParamTypes) if typeAnalyzer.frameAt(indy) != null =>
          val lmf = LambdaMetaFactoryCall(indy, samMethodType, implMethod, instantiatedMethodType)
          val capturedArgInfos = computeCapturedArgInfos(lmf, indyParamTypes, typeAnalyzer)
          methodClosureInstantiations += indy -> ClosureInstantiation(
            lmf,
            methodNode,
            definingClass,
            capturedArgInfos)

        case _ =>
      }

      callsites(methodNode) = methodCallsites
      closureInstantiations(methodNode) = methodClosureInstantiations
    }
  }

  def computeArgInfos(callee: Either[OptimizerWarning, Callee], callsiteInsn: MethodInsnNode, paramTps: FLazy[Array[Type]], typeAnalyzer: NonLubbingTypeFlowAnalyzer): IntMap[ArgInfo] = {
    if (callee.isLeft) IntMap.empty
    else {
      val numArgs = FLazy(paramTps.get.length + (if (callsiteInsn.getOpcode == Opcodes.INVOKESTATIC) 0 else 1))
      argInfosForSams(callee.get.samParamTypes, callsiteInsn, numArgs, typeAnalyzer)
    }
  }

  def computeCapturedArgInfos(lmf: LambdaMetaFactoryCall, indyParamTypes: Array[Type], typeAnalyzer: NonLubbingTypeFlowAnalyzer): IntMap[ArgInfo] = {
    val capturedTypes = indyParamTypes.map(t => bTypeForDescriptorFromClassfile(t.getDescriptor))
    val capturedSams = samTypes(capturedTypes)
    argInfosForSams(capturedSams, lmf.indy, FLazy(indyParamTypes.length), typeAnalyzer)
  }

  private def argInfosForSams(sams: IntMap[ClassBType], consumerInsn: AbstractInsnNode, numConsumed: FLazy[Int], typeAnalyzer: NonLubbingTypeFlowAnalyzer): IntMap[ArgInfo] = {
    lazy val consumerFrame = typeAnalyzer.frameAt(consumerInsn)
    lazy val firstConsumedSlot = consumerFrame.stackTop - numConsumed.get + 1
    val samInfos: IntMap[ArgInfo] = sams flatMap {
      case (index, _) =>
        val argInfo = consumerFrame.getValue(firstConsumedSlot + index) match {
          case _: LMFValue => Some(FunctionLiteral)
          case p: ParamValue => Some(ForwardedParam(p.local))
          case _ => None
        }
        argInfo.map((index, _))
    }
    val isArrayLoadOrUpdateOnKnownArray = BackendUtils.isRuntimeArrayLoadOrUpdate(consumerInsn) &&
      consumerFrame.getValue(firstConsumedSlot + 1).getType.getSort == Type.ARRAY
    if (isArrayLoadOrUpdateOnKnownArray) samInfos.updated(1, StaticallyKnownArray)
    else samInfos
  }

  def samParamTypes(methodNode: MethodNode, paramTps: Array[Type], receiverType: ClassBType): IntMap[ClassBType] = {
    val paramTypes = {
      val params = paramTps.map(t => bTypeForDescriptorFromClassfile(t.getDescriptor))
      val isStatic = BytecodeUtils.isStaticMethod(methodNode)
      if (isStatic) params else receiverType +: params
    }
    samTypes(paramTypes)
  }

  private def samTypes(types: Array[BType]): IntMap[ClassBType] = {
    var res = IntMap.empty[ClassBType]
    for (i <- types.indices) {
      types(i) match {
        case c: ClassBType =>
          if (c.info.get.inlineInfo.sam.isDefined) res = res.updated(i, c)

        case _ =>
      }
    }
    res
  }

  final class FLazy[@specialized(Int) T](_init: => T) {
    private[this] var init = () => _init
    private[this] var v: T = _
    def get: T = {
      if (init != null) {
        v = init()
        init = null
      }
      v
    }
  }

  object FLazy {
    def apply[T](init: => T): FLazy[T] = new FLazy(init)
  }

  /**
   * Just a named tuple used as return type of `analyzeCallsite`.
   */
  private case class CallsiteInfo(isStaticallyResolved: Boolean, sourceFilePath: Option[String],
                                  annotatedInline: Boolean, annotatedNoInline: Boolean,
                                  samParamTypes: IntMap[ClassBType],
                                  warning: Option[CalleeInfoWarning])

  /**
   * Analyze a callsite and gather meta-data that can be used for inlining decisions.
   */
  private def analyzeCallsite(calleeMethodNode: MethodNode, calleeDeclarationClassBType: ClassBType, call: MethodInsnNode, paramTps: FLazy[Array[Type]], calleeSourceFilePath: Option[String], callsiteClass: ClassBType): CallsiteInfo = {
    val methodSignature = (calleeMethodNode.name, calleeMethodNode.desc)

    try {
      // The inlineInfo.methodInfos of a ClassBType holds an InlineInfo for each method *declared*
      // within a class (not for inherited methods). Since we already have the  classBType of the
      // callee, we only check there for the methodInlineInfo, we should find it there.
      calleeDeclarationClassBType.info.orThrow.inlineInfo.methodInfos.get(methodSignature) match {
        case Some(methodInlineInfo) =>
          val receiverType = classBTypeFromParsedClassfile(call.owner)
          // (1) Special case for trait super accessors. trait T { def f = 1 } generates a static
          // method t$ which calls `invokespecial T.f`. Even if `f` is not final, this call will
          // always resolve to `T.f`. This is a (very) special case. Otherwise, `invokespecial`
          // is only used for private methods, constructors and super calls.
          //
          // (2) A non-final method can be safe to inline if the receiver type is a final subclass. Example:
          //   class A { @inline def f = 1 }; object B extends A; B.f  // can be inlined
          //
          // TODO: (2) doesn't cover the following example:
          //   trait TravLike { def map = ... }
          //   sealed trait List extends TravLike { ... } // assume map is not overridden
          //   final case class :: / final case object Nil
          //   (l: List).map // can be inlined
          // we need to know that
          //   - the receiver is sealed
          //   - what are the children of the receiver
          //   - all children are final
          //   - none of the children overrides map
          //
          // TODO: type analysis can render more calls statically resolved. Example:
          //   new A.f  // can be inlined, the receiver type is known to be exactly A.
          val isStaticallyResolved: Boolean = {
            isStaticCallsite(call) ||
              (call.getOpcode == Opcodes.INVOKESPECIAL && receiverType == callsiteClass) || // (1)
              methodInlineInfo.effectivelyFinal ||
              receiverType.info.orThrow.inlineInfo.isEffectivelyFinal // (2)
          }

          val warning = calleeDeclarationClassBType.info.orThrow.inlineInfo.warning.map(
            MethodInlineInfoIncomplete(calleeDeclarationClassBType.internalName, calleeMethodNode.name, calleeMethodNode.desc, _))

          CallsiteInfo(
            isStaticallyResolved = isStaticallyResolved,
            sourceFilePath       = calleeSourceFilePath,
            annotatedInline      = methodInlineInfo.annotatedInline,
            annotatedNoInline    = methodInlineInfo.annotatedNoInline,
            samParamTypes        = samParamTypes(calleeMethodNode, paramTps.get, receiverType),
            warning              = warning)

        case None =>
          val warning = MethodInlineInfoMissing(calleeDeclarationClassBType.internalName, calleeMethodNode.name, calleeMethodNode.desc, calleeDeclarationClassBType.info.orThrow.inlineInfo.warning)
          CallsiteInfo(false, None, false, false, IntMap.empty, Some(warning))
      }
    } catch {
      case Invalid(noInfo: NoClassBTypeInfo) =>
        val warning = MethodInlineInfoError(calleeDeclarationClassBType.internalName, calleeMethodNode.name, calleeMethodNode.desc, noInfo)
        CallsiteInfo(false, None, false, false, IntMap.empty, Some(warning))
    }
  }

    /**
   * A callsite in the call graph.
   *
   * @param callsiteInstruction The invocation instruction
   * @param callsiteMethod      The method containing the callsite
   * @param callsiteClass       The class containing the callsite
   * @param callee              The callee, as it appears in the invocation instruction. For virtual
   *                            calls, an override of the callee might be invoked. Also, the callee
   *                            can be abstract. Contains a warning message if the callee MethodNode
   *                            cannot be found in the bytecode repository.
   * @param argInfos            Information about the invocation receiver and arguments
   * @param callsiteStackHeight The stack height at the callsite, required by the inliner
   * @param callsitePosition    The source position of the callsite, used for inliner warnings.
   */
  final case class Callsite(callsiteInstruction: MethodInsnNode, callsiteMethod: MethodNode, callsiteClass: ClassBType,
                            callee: Either[OptimizerWarning, Callee], argInfos: IntMap[ArgInfo],
                            callsiteStackHeight: Int, receiverKnownNotNull: Boolean, callsitePosition: Position,
                            annotatedInline: Boolean, annotatedNoInline: Boolean) {
    // an annotation at the callsite takes precedence over an annotation at the definition site
    def isInlineAnnotated = annotatedInline || (callee.get.annotatedInline && !annotatedNoInline)
    def isNoInlineAnnotated = annotatedNoInline || (callee.get.annotatedNoInline && !annotatedInline)

    override def toString =
      "Invocation of" +
        s" ${callee.map(_.calleeDeclarationClass.internalName).getOrElse("?")}.${callsiteInstruction.name + callsiteInstruction.desc}" +
        s"@${callsiteMethod.instructions.indexOf(callsiteInstruction)}" +
        s" in ${callsiteClass.internalName}.${callsiteMethod.name}${callsiteMethod.desc}"
  }

  /**
   * Information about invocation arguments, obtained through data flow analysis of the callsite method.
   */
  sealed trait ArgInfo
  case object FunctionLiteral extends ArgInfo
  final case class ForwardedParam(index: Int) extends ArgInfo
  case object StaticallyKnownArray extends ArgInfo
  //  final case class ArgTypeInfo(argType: BType, isPrecise: Boolean, knownNotNull: Boolean) extends ArgInfo
  // can be extended, e.g., with constant types

  /**
   * A callee in the call graph.
   *
   * @param callee                 The callee, as it appears in the invocation instruction. For
   *                               virtual calls, an override of the callee might be invoked. Also,
   *                               the callee can be abstract.
   * @param calleeDeclarationClass The class in which the callee is declared
   * @param isStaticallyResolved   True if the callee cannot be overridden
   * @param annotatedInline        True if the callee is annotated @inline
   * @param annotatedNoInline      True if the callee is annotated @noinline
   * @param samParamTypes          A map from parameter positions to SAM parameter types
   * @param calleeInfoWarning      An inliner warning if some information was not available while
   *                               gathering the information about this callee.
   */
  final case class Callee(callee: MethodNode, calleeDeclarationClass: ClassBType,
                          isStaticallyResolved: Boolean, sourceFilePath: Option[String],
                          annotatedInline: Boolean, annotatedNoInline: Boolean,
                          samParamTypes: IntMap[ClassBType],
                          calleeInfoWarning: Option[CalleeInfoWarning]) {
    override def toString = s"Callee($calleeDeclarationClass.${callee.name})"

    def canInlineFromSource = inlinerHeuristics.canInlineFromSource(sourceFilePath, calleeDeclarationClass.internalName)
    def isAbstract = isAbstractMethod(callee)
    def isSpecialMethod = isConstructor(callee) || isNativeMethod(callee) || hasCallerSensitiveAnnotation(callee)

    def safeToInline = isStaticallyResolved && canInlineFromSource && !isAbstract && !isSpecialMethod
  }

  /**
   * Metadata about a closure instantiation, stored in the call graph
   *
   * @param lambdaMetaFactoryCall the InvokeDynamic instruction
   * @param ownerMethod           the method where the closure is allocated
   * @param ownerClass            the class containing the above method
   * @param capturedArgInfos      information about captured arguments. Used for updating the call
   *                              graph when re-writing a closure invocation to the body method.
   */
  final case class ClosureInstantiation(lambdaMetaFactoryCall: LambdaMetaFactoryCall, ownerMethod: MethodNode, ownerClass: ClassBType, capturedArgInfos: IntMap[ArgInfo]) {
    override def toString = s"ClosureInstantiation($lambdaMetaFactoryCall, ${ownerMethod.name + ownerMethod.desc}, $ownerClass)"
  }
}