// Copyright (c) 2020, 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.synthesis;

import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.DexAnnotation;
import com.android.tools.r8.graph.DexApplication;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.GraphLens;
import com.android.tools.r8.graph.GraphLens.Builder;
import com.android.tools.r8.shaking.MainDexClasses;
import com.android.tools.r8.utils.DescriptorUtils;
import com.android.tools.r8.utils.InternalOptions;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ListMultimap;
import com.google.common.hash.HashCode;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeSet;
import java.util.function.Predicate;

public class SyntheticFinalization {

  public static class Result {
    public final CommittedItems commit;
    public final ImmutableSet<DexType> removedSyntheticClasses;

    public Result(CommittedItems commit, ImmutableSet<DexType> removedSyntheticClasses) {
      this.commit = commit;
      this.removedSyntheticClasses = removedSyntheticClasses;
    }
  }

  private static class EquivalenceGroup<T extends SyntheticDefinition & Comparable<T>>
      implements Comparable<EquivalenceGroup<T>> {
    private List<T> members;

    EquivalenceGroup(T singleton) {
      this(singleton, Collections.singletonList(singleton));
    }

    EquivalenceGroup(T representative, List<T> members) {
      assert !members.isEmpty();
      assert members.get(0) == representative;
      this.members = members;
    }

    T getRepresentative() {
      return members.get(0);
    }

    public List<T> getMembers() {
      return members;
    }

    @Override
    public int compareTo(EquivalenceGroup<T> other) {
      return getRepresentative().compareTo(other.getRepresentative());
    }
  }

  private final InternalOptions options;
  private final ImmutableSet<DexType> legacySyntheticTypes;
  private final ImmutableMap<DexType, SyntheticReference> syntheticItems;

  SyntheticFinalization(
      InternalOptions options,
      ImmutableSet<DexType> legacySyntheticTypes,
      ImmutableMap<DexType, SyntheticReference> syntheticItems) {
    this.options = options;
    this.legacySyntheticTypes = legacySyntheticTypes;
    this.syntheticItems = syntheticItems;
  }

  public Result computeFinalSynthetics(AppView<?> appView) {
    assert verifyNoNestedSynthetics();
    DexApplication application = appView.appInfo().app();
    MainDexClasses mainDexClasses = appView.appInfo().getMainDexClasses();
    GraphLens graphLens = appView.graphLens();

    List<SyntheticMethodDefinition> methodDefinitions =
        lookupSyntheticMethodDefinitions(application);

    Map<HashCode, List<SyntheticMethodDefinition>> potentialEquivalences =
        computePotentialEquivalences(methodDefinitions);

    Map<DexType, EquivalenceGroup<SyntheticMethodDefinition>> equivalences =
        computeActualEquivalences(potentialEquivalences, options.itemFactory);

    Builder lensBuilder = GraphLens.builder();
    List<DexProgramClass> newProgramClasses = new ArrayList<>();
    List<DexProgramClass> finalSyntheticClasses = new ArrayList<>();
    buildLensAndProgram(
        application,
        equivalences,
        syntheticItems::containsKey,
        mainDexClasses,
        lensBuilder,
        options.itemFactory,
        newProgramClasses,
        finalSyntheticClasses);

    newProgramClasses.addAll(finalSyntheticClasses);

    handleSynthesizedClassMapping(finalSyntheticClasses, application, options, mainDexClasses);

    DexApplication app = application.builder().replaceProgramClasses(newProgramClasses).build();

    appView.setGraphLens(lensBuilder.build(options.itemFactory, graphLens));
    assert appView.appInfo().getMainDexClasses() == mainDexClasses;
    return new Result(
        new CommittedItems(
            SyntheticItems.INVALID_ID_AFTER_SYNTHETIC_FINALIZATION,
            app,
            legacySyntheticTypes,
            ImmutableMap.of(),
            ImmutableList.of()),
        syntheticItems.keySet());
  }

  private boolean verifyNoNestedSynthetics() {
    for (SyntheticReference item : syntheticItems.values()) {
      // Check that a context is never a synthetic unless it is an input, thus its own context.
      assert item.getHolder() == item.getContextType()
          || !syntheticItems.containsKey(item.getContextType());
    }
    return true;
  }

  private void handleSynthesizedClassMapping(
      List<DexProgramClass> finalSyntheticClasses,
      DexApplication application,
      InternalOptions options,
      MainDexClasses mainDexClasses) {
    if (options.intermediate) {
      updateSynthesizedClassMapping(application, finalSyntheticClasses);
    }
    updateMainDexListWithSynthesizedClassMap(application, mainDexClasses);
    if (!options.intermediate) {
      clearSynthesizedClassMapping(application);
    }
  }

  private void updateSynthesizedClassMapping(
      DexApplication application, List<DexProgramClass> finalSyntheticClasses) {
    ListMultimap<DexProgramClass, DexProgramClass> originalToSynthesized =
        ArrayListMultimap.create();
    for (DexType type : legacySyntheticTypes) {
      DexProgramClass clazz = DexProgramClass.asProgramClassOrNull(application.definitionFor(type));
      if (clazz != null) {
        for (DexProgramClass origin : clazz.getSynthesizedFrom()) {
          originalToSynthesized.put(origin, clazz);
        }
      }
    }
    for (DexProgramClass clazz : finalSyntheticClasses) {
      for (DexProgramClass origin : clazz.getSynthesizedFrom()) {
        originalToSynthesized.put(origin, clazz);
      }
    }
    for (Map.Entry<DexProgramClass, Collection<DexProgramClass>> entry :
        originalToSynthesized.asMap().entrySet()) {
      DexProgramClass original = entry.getKey();
      // Use a tree set to make sure that we have an ordering on the types.
      // These types are put in an array in annotations in the output and we
      // need a consistent ordering on them.
      TreeSet<DexType> synthesized = new TreeSet<>(DexType::slowCompareTo);
      entry.getValue().stream()
          .map(dexProgramClass -> dexProgramClass.type)
          .forEach(synthesized::add);
      synthesized.addAll(
          DexAnnotation.readAnnotationSynthesizedClassMap(original, application.dexItemFactory));

      DexAnnotation updatedAnnotation =
          DexAnnotation.createAnnotationSynthesizedClassMap(
              synthesized, application.dexItemFactory);

      original.setAnnotations(original.annotations().getWithAddedOrReplaced(updatedAnnotation));
    }
  }

  private void updateMainDexListWithSynthesizedClassMap(
      DexApplication application, MainDexClasses mainDexClasses) {
    if (mainDexClasses.isEmpty()) {
      return;
    }
    List<DexProgramClass> newMainDexClasses = new ArrayList<>();
    mainDexClasses.forEach(
        dexType -> {
          DexProgramClass programClass =
              DexProgramClass.asProgramClassOrNull(application.definitionFor(dexType));
          if (programClass != null) {
            Collection<DexType> derived =
                DexAnnotation.readAnnotationSynthesizedClassMap(
                    programClass, application.dexItemFactory);
            for (DexType type : derived) {
              DexProgramClass syntheticClass =
                  DexProgramClass.asProgramClassOrNull(application.definitionFor(type));
              if (syntheticClass != null) {
                newMainDexClasses.add(syntheticClass);
              }
            }
          }
        });
    mainDexClasses.addAll(newMainDexClasses);
  }

  private void clearSynthesizedClassMapping(DexApplication application) {
    for (DexProgramClass clazz : application.classes()) {
      clazz.setAnnotations(
          clazz.annotations().getWithout(application.dexItemFactory.annotationSynthesizedClassMap));
    }
  }

  private static void buildLensAndProgram(
      DexApplication app,
      Map<DexType, EquivalenceGroup<SyntheticMethodDefinition>> syntheticMethodGroups,
      Predicate<DexType> isSyntheticType,
      MainDexClasses mainDexClasses,
      Builder lensBuilder,
      DexItemFactory factory,
      List<DexProgramClass> normalClasses,
      List<DexProgramClass> newSyntheticClasses) {

    for (DexProgramClass clazz : app.classes()) {
      if (!isSyntheticType.test(clazz.type)) {
        normalClasses.add(clazz);
      }
    }

    syntheticMethodGroups.forEach(
        (syntheticType, syntheticGroup) -> {
          SyntheticMethodDefinition firstMember = syntheticGroup.getRepresentative();
          SynthesizingContext context = firstMember.getContext();
          SyntheticClassBuilder builder =
              new SyntheticClassBuilder(syntheticType, context, factory);
          // TODO(b/158159959): Support grouping multiple methods per synthetic class.
          builder.addMethod(
              methodBuilder -> {
                DexEncodedMethod definition = firstMember.getMethod().getDefinition();
                methodBuilder
                    .setAccessFlags(definition.accessFlags)
                    .setProto(definition.getProto())
                    .setCode(m -> definition.getCode());
              });
          DexProgramClass externalSyntheticClass = builder.build();
          assert externalSyntheticClass.getMethodCollection().size() == 1;
          DexEncodedMethod externalSyntheticMethod =
              externalSyntheticClass.methods().iterator().next();
          newSyntheticClasses.add(externalSyntheticClass);
          for (SyntheticMethodDefinition member : syntheticGroup.getMembers()) {
            lensBuilder.map(
                member.getMethod().getHolder().getType(), externalSyntheticClass.getType());
            lensBuilder.map(member.getMethod().getReference(), externalSyntheticMethod.method);
            DexType memberContext = member.getContextType();
            DexProgramClass from =
                DexProgramClass.asProgramClassOrNull(app.definitionFor(memberContext));
            if (from != null) {
              externalSyntheticClass.addSynthesizedFrom(from);
              if (mainDexClasses.contains(from)) {
                mainDexClasses.add(externalSyntheticClass);
              }
            }
          }
        });
  }

  private static <T extends SyntheticDefinition & Comparable<T>>
      Map<DexType, EquivalenceGroup<T>> computeActualEquivalences(
          Map<HashCode, List<T>> potentialEquivalences, DexItemFactory factory) {
    Map<DexType, List<EquivalenceGroup<T>>> groupsPerContext = new IdentityHashMap<>();
    potentialEquivalences.forEach(
        (hash, members) -> {
          // Get a representative member and add to its group.
          T representative = findDeterministicRepresentative(members);
          List<T> group = new ArrayList<>(members.size());
          group.add(representative);
          // Each other member is in the shared group if it is actually equal to the first member.
          for (T member : members) {
            if (member != representative) {
              if (member.isEquivalentTo(representative)) {
                group.add(member);
              } else {
                // The member becomes a new singleton group.
                // TODO(b/158159959): Consider checking for sub-groups of matching members.
                groupsPerContext
                    .computeIfAbsent(member.getContextType(), k -> new ArrayList<>())
                    .add(new EquivalenceGroup<>(member));
              }
            }
          }
          groupsPerContext
              .computeIfAbsent(representative.getContextType(), k -> new ArrayList<>())
              .add(new EquivalenceGroup<>(representative, group));
        });
    Map<DexType, EquivalenceGroup<T>> equivalences = new IdentityHashMap<>();
    groupsPerContext.forEach(
        (context, groups) -> {
          groups.sort(EquivalenceGroup::compareTo);
          for (int i = 0; i < groups.size(); i++) {
            equivalences.put(createExternalType(context, i, factory), groups.get(i));
          }
        });
    return equivalences;
  }

  private static <T extends SyntheticDefinition & Comparable<T>> T findDeterministicRepresentative(
      List<T> members) {
    // Pick a deterministic member as representative.
    T smallest = members.get(0);
    for (int i = 1; i < members.size(); i++) {
      T next = members.get(i);
      if (next.compareTo(smallest) < 0) {
        smallest = next;
      }
    }
    return smallest;
  }

  private static DexType createExternalType(
      DexType representativeContext, int nextContextId, DexItemFactory factory) {
    return factory.createType(
        DescriptorUtils.getDescriptorFromClassBinaryName(
            representativeContext.getInternalName()
                + SyntheticItems.EXTERNAL_SYNTHETIC_CLASS_SEPARATOR
                + nextContextId));
  }

  private static <T extends SyntheticDefinition>
      Map<HashCode, List<T>> computePotentialEquivalences(List<T> definitions) {
    Map<HashCode, List<T>> equivalences = new HashMap<>(definitions.size());
    for (T definition : definitions) {
      HashCode hash = definition.computeHash();
      equivalences.computeIfAbsent(hash, k -> new ArrayList<>()).add(definition);
    }
    return equivalences;
  }

  private List<SyntheticMethodDefinition> lookupSyntheticMethodDefinitions(
      DexApplication finalApp) {
    List<SyntheticMethodDefinition> methods = new ArrayList<>(syntheticItems.size());
    for (SyntheticReference reference : syntheticItems.values()) {
      SyntheticDefinition definition = reference.lookupDefinition(finalApp::definitionFor);
      assert definition != null;
      assert definition instanceof SyntheticMethodDefinition;
      if (definition != null && definition instanceof SyntheticMethodDefinition) {
        methods.add(((SyntheticMethodDefinition) definition));
      }
    }
    return methods;
  }
}