// 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.androidapi;

import static com.android.tools.r8.utils.MapUtils.ignoreKey;

import com.android.tools.r8.errors.MissingGlobalSyntheticsConsumerDiagnostic;
import com.android.tools.r8.errors.Unreachable;
import com.android.tools.r8.graph.AppInfo;
import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.Code;
import com.android.tools.r8.graph.DexClass;
import com.android.tools.r8.graph.DexCode.TryHandler;
import com.android.tools.r8.graph.DexCode.TryHandler.TypeAddrPair;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexLibraryClass;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.MethodAccessFlags;
import com.android.tools.r8.graph.ThrowExceptionCode;
import com.android.tools.r8.shaking.AppInfoWithLiveness;
import com.android.tools.r8.synthesis.CommittedItems;
import com.android.tools.r8.synthesis.SyntheticItems;
import com.android.tools.r8.utils.ListUtils;
import com.android.tools.r8.utils.ThreadUtils;
import com.android.tools.r8.utils.WorkList;
import com.google.common.collect.Sets;
import java.util.Arrays;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;

/**
 * The only instructions we do not outline is constant classes, instance-of/checkcast and exception
 * guards. For program classes we also visit super types if these are library otherwise we will
 * visit the program super type's super types when visiting that program class.
 */
public class ApiReferenceStubber {

  private final AppView<?> appView;
  private final Map<DexLibraryClass, Set<DexProgramClass>> referencingContexts =
      new ConcurrentHashMap<>();
  private final Set<DexLibraryClass> libraryClassesToMock = Sets.newConcurrentHashSet();
  private final Set<DexType> seenTypes = Sets.newConcurrentHashSet();
  private final AndroidApiLevelCompute apiLevelCompute;
  private final ApiReferenceStubberEventConsumer eventConsumer;

  public ApiReferenceStubber(AppView<?> appView) {
    this.appView = appView;
    this.apiLevelCompute = appView.apiLevelCompute();
    this.eventConsumer = ApiReferenceStubberEventConsumer.create(appView);
  }

  public void run(ExecutorService executorService) throws ExecutionException {
    if (appView.options().isGeneratingDex()
        && appView.options().apiModelingOptions().enableStubbingOfClasses) {
      Collection<DexProgramClass> classes =
          ListUtils.filter(
              appView.appInfo().classes(), DexProgramClass::originatesFromClassResource);
      // Finding super types is really fast so no need to pay the overhead of threading if the
      // number of classes is low.
      if (classes.size() > 2) {
        ThreadUtils.processItems(classes, this::processClass, executorService);
      } else {
        classes.forEach(this::processClass);
      }
    }
    if (!libraryClassesToMock.isEmpty()) {
      libraryClassesToMock.forEach(
          clazz ->
              mockMissingLibraryClass(
                  clazz,
                  ThrowExceptionCode.create(appView.dexItemFactory().noClassDefFoundErrorType),
                  eventConsumer));
      // Commit the synthetic items.
      CommittedItems committedItems = appView.getSyntheticItems().commit(appView.appInfo().app());
      if (appView.hasLiveness()) {
        AppView<AppInfoWithLiveness> appInfoWithLivenessAppView = appView.withLiveness();
        appInfoWithLivenessAppView.setAppInfo(
            appInfoWithLivenessAppView.appInfo().rebuildWithLiveness(committedItems));
      } else if (appView.hasClassHierarchy()) {
        appView
            .withClassHierarchy()
            .setAppInfo(
                appView.appInfo().withClassHierarchy().rebuildWithClassHierarchy(committedItems));
      } else {
        appView
            .withoutClassHierarchy()
            .setAppInfo(
                new AppInfo(
                    appView.appInfo().getSyntheticItems().commit(appView.app()),
                    appView.appInfo().getMainDexInfo()));
      }
    }
    eventConsumer.finished(appView);
  }

  private boolean isAlreadyOutlined(DexProgramClass clazz) {
    SyntheticItems syntheticItems = appView.getSyntheticItems();
    return syntheticItems.isSyntheticOfKind(clazz.getType(), kinds -> kinds.API_MODEL_OUTLINE)
        || syntheticItems.isSyntheticOfKind(
            clazz.getType(), kinds -> kinds.API_MODEL_OUTLINE_WITHOUT_GLOBAL_MERGING);
  }

  public void processClass(DexProgramClass clazz) {
    assert clazz.originatesFromClassResource();
    if (isAlreadyOutlined(clazz)) {
      return;
    }
    // We cannot reliably create a stub that will have the same throwing behavior for all VMs.
    // Only create stubs for exceptions to allow them being present in catch handlers and super
    // types of existing program classes. See b/258270051 and b/259076765 for more information.
    clazz
        .allImmediateSupertypes()
        .forEach(superType -> findReferencedLibraryClasses(superType, clazz));
    clazz.forEachProgramMethodMatching(
        DexEncodedMethod::hasCode,
        method -> {
          Code code = method.getDefinition().getCode();
          if (!code.isDexCode()) {
            return;
          }
          for (TryHandler handler : code.asDexCode().getHandlers()) {
            for (TypeAddrPair pair : handler.pairs) {
              DexType rewrittenType = appView.graphLens().lookupType(pair.getType());
              findReferencedLibraryClasses(rewrittenType, clazz);
            }
          }
        });
  }

  private void findReferencedLibraryClasses(DexType type, DexProgramClass context) {
    if (!type.isClassType() || isJavaType(type)) {
      return;
    }
    WorkList.newIdentityWorkList(type, seenTypes)
        .process(
            (classType, workList) -> {
              DexClass clazz = appView.definitionFor(classType);
              if (clazz == null || !clazz.isLibraryClass()) {
                return;
              }
              ComputedApiLevel androidApiLevel =
                  apiLevelCompute.computeApiLevelForLibraryReference(
                      clazz.type, ComputedApiLevel.unknown());
              if (androidApiLevel.isGreaterThan(appView.computedMinApiLevel())
                  && androidApiLevel.isKnownApiLevel()) {
                workList.addIfNotSeen(clazz.allImmediateSupertypes());
                libraryClassesToMock.add(clazz.asLibraryClass());
                referencingContexts
                    .computeIfAbsent(clazz.asLibraryClass(), ignoreKey(Sets::newConcurrentHashSet))
                    .add(context);
              }
            });
  }

  private boolean isJavaType(DexType type) {
    return type == appView.dexItemFactory().objectType
        || type.getDescriptor().startsWith(appView.dexItemFactory().javaDescriptorPrefix);
  }

  private void mockMissingLibraryClass(
      DexLibraryClass libraryClass,
      ThrowExceptionCode throwExceptionCode,
      ApiReferenceStubberEventConsumer eventConsumer) {
    DexItemFactory factory = appView.dexItemFactory();
    // Do not stub the anything starting with java (including the object type).
    if (isJavaType(libraryClass.getType())) {
      return;
    }
    // Check if desugared library will bridge the type.
    if (appView
        .options()
        .machineDesugaredLibrarySpecification
        .isSupported(libraryClass.getType())) {
      return;
    }
    Set<DexProgramClass> contexts = referencingContexts.get(libraryClass);
    if (contexts == null) {
      throw new Unreachable("Attempt to create a global synthetic with no contexts");
    }
    DexProgramClass mockClass =
        appView
            .appInfo()
            .getSyntheticItems()
            .ensureGlobalClass(
                () -> new MissingGlobalSyntheticsConsumerDiagnostic("API stubbing"),
                kinds -> kinds.API_MODEL_STUB,
                libraryClass.getType(),
                contexts,
                appView,
                classBuilder -> {
                  classBuilder
                      .setSuperType(libraryClass.getSuperType())
                      .setInterfaces(Arrays.asList(libraryClass.getInterfaces().values))
                      // Add throwing static initializer
                      .addMethod(
                          methodBuilder ->
                              methodBuilder
                                  .setName(factory.classConstructorMethodName)
                                  .setProto(factory.createProto(factory.voidType))
                                  .setAccessFlags(MethodAccessFlags.createForClassInitializer())
                                  .setCode(method -> throwExceptionCode));
                  if (libraryClass.isInterface()) {
                    classBuilder.setInterface();
                  }
                  if (!libraryClass.isFinal()) {
                    classBuilder.unsetFinal();
                  }
                },
                clazz -> eventConsumer.acceptMockedLibraryClass(clazz, libraryClass));
    if (!eventConsumer.isEmpty()) {
      for (DexProgramClass context : contexts) {
        eventConsumer.acceptMockedLibraryClassContext(mockClass, libraryClass, context);
      }
    }
  }
}