// Copyright (c) 2021, the R8 project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
package com.android.tools.r8.ir.desugar.itf;

import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.CfCode;
import com.android.tools.r8.graph.DexClass;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.graph.DexString;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.MethodAccessFlags;
import com.android.tools.r8.graph.ProgramMethod;
import com.android.tools.r8.ir.desugar.CfClassSynthesizerDesugaring;
import com.android.tools.r8.ir.desugar.CfClassSynthesizerDesugaringEventConsumer;
import com.android.tools.r8.ir.desugar.itf.EmulatedInterfaceSynthesizerEventConsumer.L8ProgramEmulatedInterfaceSynthesizerEventConsumer;
import com.android.tools.r8.ir.synthetic.EmulateDispatchSyntheticCfCodeProvider;
import com.android.tools.r8.synthesis.SyntheticMethodBuilder;
import com.android.tools.r8.synthesis.SyntheticNaming;
import com.android.tools.r8.synthesis.SyntheticProgramClassBuilder;
import com.android.tools.r8.utils.Pair;
import com.android.tools.r8.utils.StringDiagnostic;
import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

public final class ProgramEmulatedInterfaceSynthesizer implements CfClassSynthesizerDesugaring {

  private final AppView<?> appView;
  private final InterfaceDesugaringSyntheticHelper helper;
  private final Map<DexType, List<DexType>> emulatedInterfacesHierarchy;

  public static ProgramEmulatedInterfaceSynthesizer create(AppView<?> appView) {
    if (!appView.options().isDesugaredLibraryCompilation()
        || appView.options().desugaredLibrarySpecification.getEmulateLibraryInterface().isEmpty()) {
      return null;
    }
    return new ProgramEmulatedInterfaceSynthesizer(appView);
  }

  public ProgramEmulatedInterfaceSynthesizer(AppView<?> appView) {
    this.appView = appView;
    helper = new InterfaceDesugaringSyntheticHelper(appView);
    // Avoid the computation outside L8 since it is not needed.
    emulatedInterfacesHierarchy =
        appView.options().isDesugaredLibraryCompilation()
            ? processEmulatedInterfaceHierarchy()
            : Collections.emptyMap();
  }

  private Map<DexType, List<DexType>> processEmulatedInterfaceHierarchy() {
    Map<DexType, List<DexType>> emulatedInterfacesHierarchy = new IdentityHashMap<>();
    Set<DexType> processed = Sets.newIdentityHashSet();
    ArrayList<DexType> emulatedInterfacesSorted = new ArrayList<>(helper.getEmulatedInterfaces());
    emulatedInterfacesSorted.sort(DexType::compareTo);
    for (DexType interfaceType : emulatedInterfacesSorted) {
      processEmulatedInterfaceHierarchy(interfaceType, processed, emulatedInterfacesHierarchy);
    }
    return emulatedInterfacesHierarchy;
  }

  private void processEmulatedInterfaceHierarchy(
      DexType interfaceType,
      Set<DexType> processed,
      Map<DexType, List<DexType>> emulatedInterfacesHierarchy) {
    if (processed.contains(interfaceType)) {
      return;
    }
    emulatedInterfacesHierarchy.put(interfaceType, new ArrayList<>());
    processed.add(interfaceType);
    DexClass theInterface = appView.definitionFor(interfaceType);
    if (theInterface == null) {
      return;
    }
    LinkedList<DexType> workList = new LinkedList<>(Arrays.asList(theInterface.interfaces.values));
    while (!workList.isEmpty()) {
      DexType next = workList.removeLast();
      if (helper.isEmulatedInterface(next)) {
        processEmulatedInterfaceHierarchy(next, processed, emulatedInterfacesHierarchy);
        emulatedInterfacesHierarchy.get(next).add(interfaceType);
        DexClass nextClass = appView.definitionFor(next);
        if (nextClass != null) {
          workList.addAll(Arrays.asList(nextClass.interfaces.values));
        }
      }
    }
  }

  DexProgramClass synthesizeProgramEmulatedInterface(
      DexProgramClass emulatedInterface,
      L8ProgramEmulatedInterfaceSynthesizerEventConsumer eventConsumer) {
    return appView
        .getSyntheticItems()
        .ensureFixedClass(
            SyntheticNaming.SyntheticKind.EMULATED_INTERFACE_CLASS,
            emulatedInterface,
            appView,
            builder -> synthesizeEmulateInterfaceMethods(emulatedInterface, builder),
            eventConsumer::acceptProgramEmulatedInterface);
  }

  private void synthesizeEmulateInterfaceMethods(
      DexProgramClass emulatedInterface, SyntheticProgramClassBuilder builder) {
    assert helper.isEmulatedInterface(emulatedInterface.type);
    emulatedInterface.forEachProgramVirtualMethodMatching(
        DexEncodedMethod::isDefaultMethod,
        method ->
            builder.addMethod(
                methodBuilder ->
                    synthesizeEmulatedInterfaceMethod(method, emulatedInterface, methodBuilder)));
    assert builder.getType()
        == InterfaceDesugaringSyntheticHelper.getEmulateLibraryInterfaceClassType(
            emulatedInterface.type, appView.dexItemFactory());
  }

  private void synthesizeEmulatedInterfaceMethod(
      ProgramMethod method, DexProgramClass theInterface, SyntheticMethodBuilder methodBuilder) {
    assert !method.getDefinition().isStatic();
    DexMethod emulatedMethod = helper.emulateInterfaceLibraryMethod(method);
    methodBuilder
        .setName(emulatedMethod.getName())
        .setProto(emulatedMethod.getProto())
        .setAccessFlags(MethodAccessFlags.createPublicStaticSynthetic())
        .setCode(
            emulatedInterfaceMethod ->
                synthesizeCfCode(method.asProgramMethod(), theInterface, emulatedInterfaceMethod));
  }

  private CfCode synthesizeCfCode(
      ProgramMethod method, DexProgramClass theInterface, DexMethod emulatedInterfaceMethod) {
    DexMethod libraryMethod =
        method
            .getReference()
            .withHolder(helper.getEmulatedInterface(theInterface.type), appView.dexItemFactory());
    DexMethod companionMethod =
        helper.ensureDefaultAsMethodOfProgramCompanionClassStub(method).getReference();
    List<Pair<DexType, DexMethod>> extraDispatchCases =
        getDispatchCases(method, theInterface, companionMethod);
    return new EmulateDispatchSyntheticCfCodeProvider(
            emulatedInterfaceMethod.getHolderType(),
            companionMethod,
            libraryMethod,
            extraDispatchCases,
            appView)
        .generateCfCode();
  }

  private List<Pair<DexType, DexMethod>> getDispatchCases(
      ProgramMethod method, DexProgramClass theInterface, DexMethod companionMethod) {
    // To properly emulate the library interface call, we need to compute the interfaces
    // inheriting from the interface and manually implement the dispatch with instance of.
    // The list guarantees that an interface is always after interfaces it extends,
    // hence reverse iteration.
    List<DexType> subInterfaces = emulatedInterfacesHierarchy.get(theInterface.type);
    List<Pair<DexType, DexMethod>> extraDispatchCases = new ArrayList<>();
    // In practice, there is usually a single case (except for tests),
    // so we do not bother to make the following loop more clever.
    Map<DexString, Map<DexType, DexType>> retargetCoreLibMember =
        appView.options().desugaredLibrarySpecification.getRetargetCoreLibMember();
    for (DexString methodName : retargetCoreLibMember.keySet()) {
      if (method.getName() == methodName) {
        for (DexType inType : retargetCoreLibMember.get(methodName).keySet()) {
          DexClass inClass = appView.definitionFor(inType);
          if (inClass != null && implementsInterface(inClass, theInterface.type)) {
            extraDispatchCases.add(
                new Pair<>(
                    inType,
                    appView
                        .dexItemFactory()
                        .createMethod(
                            retargetCoreLibMember.get(methodName).get(inType),
                            appView
                                .dexItemFactory()
                                .protoWithDifferentFirstParameter(companionMethod.proto, inType),
                            method.getName())));
          }
        }
      }
    }
    if (subInterfaces != null) {
      for (int i = subInterfaces.size() - 1; i >= 0; i--) {
        DexClass subInterfaceClass = appView.definitionFor(subInterfaces.get(i));
        assert subInterfaceClass != null;
        assert subInterfaceClass.isProgramClass();
        // Else computation of subInterface would have failed.
        // if the method is implemented, extra dispatch is required.
        DexEncodedMethod result = subInterfaceClass.lookupVirtualMethod(method.getReference());
        if (result != null && !result.isAbstract()) {
          assert result.isDefaultMethod();
          extraDispatchCases.add(
              new Pair<>(
                  subInterfaceClass.type,
                  InterfaceDesugaringSyntheticHelper.defaultAsMethodOfCompanionClass(
                      result.getReference(), appView.dexItemFactory())));
        }
      }
    } else {
      assert extraDispatchCases.size() <= 1;
    }
    return extraDispatchCases;
  }

  private boolean implementsInterface(DexClass clazz, DexType interfaceType) {
    LinkedList<DexType> workList = new LinkedList<>(Arrays.asList(clazz.interfaces.values));
    while (!workList.isEmpty()) {
      DexType next = workList.removeLast();
      if (interfaceType == next) {
        return true;
      }
      DexClass nextClass = appView.definitionFor(next);
      if (nextClass != null) {
        workList.addAll(Arrays.asList(nextClass.interfaces.values));
      }
    }
    return false;
  }

  @Override
  public void synthesizeClasses(CfClassSynthesizerDesugaringEventConsumer eventConsumer) {
    assert appView.options().isDesugaredLibraryCompilation();
    for (DexType emulatedInterfaceType : helper.getEmulatedInterfaces()) {
      DexClass emulatedInterfaceClazz = appView.definitionFor(emulatedInterfaceType);
      if (emulatedInterfaceClazz == null || !emulatedInterfaceClazz.isProgramClass()) {
        warnMissingEmulatedInterface(emulatedInterfaceType);
        continue;
      }
      DexProgramClass emulatedInterface = emulatedInterfaceClazz.asProgramClass();
      assert emulatedInterface != null;
      if (!appView.isAlreadyLibraryDesugared(emulatedInterface)
          && needsEmulateInterfaceLibrary(emulatedInterface)) {
        synthesizeProgramEmulatedInterface(emulatedInterface, eventConsumer);
      }
    }
  }

  private boolean needsEmulateInterfaceLibrary(DexClass emulatedInterface) {
    return Iterables.any(emulatedInterface.methods(), DexEncodedMethod::isDefaultMethod);
  }

  private void warnMissingEmulatedInterface(DexType interfaceType) {
    StringDiagnostic warning =
        new StringDiagnostic(
            "Cannot emulate interface "
                + interfaceType.getName()
                + " because the interface is missing.");
    appView.options().reporter.warning(warning);
  }
}