// Copyright (c) 2022, 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.optimize.proto;

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

import com.android.tools.r8.errors.Unreachable;
import com.android.tools.r8.graph.AppView;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexMethodSignature;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.graph.DexString;
import com.android.tools.r8.graph.DexTypeList;
import com.android.tools.r8.graph.GenericSignature.MethodTypeSignature;
import com.android.tools.r8.graph.ObjectAllocationInfoCollection;
import com.android.tools.r8.graph.ProgramMethod;
import com.android.tools.r8.graph.proto.RewrittenPrototypeDescription;
import com.android.tools.r8.shaking.AppInfoWithLiveness;
import com.android.tools.r8.shaking.KeepMethodInfo;
import com.android.tools.r8.utils.InternalOptions;
import com.android.tools.r8.utils.IterableUtils;
import com.android.tools.r8.utils.MapUtils;
import com.android.tools.r8.utils.ThreadUtils;
import com.android.tools.r8.utils.Timing;
import com.android.tools.r8.utils.WorkList;
import com.android.tools.r8.utils.collections.BidirectionalOneToOneHashMap;
import com.android.tools.r8.utils.collections.DexMethodSignatureSet;
import com.android.tools.r8.utils.collections.MutableBidirectionalOneToOneMap;
import com.google.common.collect.Iterables;
import com.google.common.collect.Sets;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;

public class ProtoNormalizer {

  private final AppView<AppInfoWithLiveness> appView;
  private final DexItemFactory dexItemFactory;
  private final InternalOptions options;

  public ProtoNormalizer(AppView<AppInfoWithLiveness> appView) {
    this.appView = appView;
    this.dexItemFactory = appView.dexItemFactory();
    this.options = appView.options();
  }

  public void run(ExecutorService executorService, Timing timing) throws ExecutionException {
    timing.time("Proto normalization", () -> run(executorService));
  }

  private void run(ExecutorService executorService) throws ExecutionException {
    GlobalReservationState globalReservationState = computeGlobalReservationState(executorService);

    // TODO(b/173398086): This uses a single LocalReservationState for the entire program. This
    //  should process the strongly connected program components in parallel, each with their own
    //  LocalReservationState.
    LocalReservationState localReservationState = new LocalReservationState();
    ProtoNormalizerGraphLens.Builder lensBuilder = ProtoNormalizerGraphLens.builder(appView);
    for (DexProgramClass clazz : appView.appInfo().classesWithDeterministicOrder()) {
      Map<DexMethodSignature, DexMethodSignature> newInstanceInitializerSignatures =
          computeNewInstanceInitializerSignatures(
              clazz, localReservationState, globalReservationState);
      clazz
          .getMethodCollection()
          .replaceMethods(
              method -> {
                DexMethodSignature methodSignature = method.getSignature();
                DexMethodSignature newMethodSignature =
                    method.isInstanceInitializer()
                        ? newInstanceInitializerSignatures.get(methodSignature)
                        : localReservationState.getAndReserveNewMethodSignature(
                            methodSignature, dexItemFactory, globalReservationState);
                if (methodSignature.equals(newMethodSignature)) {
                  return method;
                }
                DexMethod newMethodReference = newMethodSignature.withHolder(clazz, dexItemFactory);
                RewrittenPrototypeDescription prototypeChanges =
                    lensBuilder.recordNewMethodSignature(method, newMethodReference);
                // TODO(b/195112263): Assert that the method does not have any optimization info.
                //  If/when enabling proto normalization after the final round of tree shaking, this
                //  should simply clear the optimization info, or replace it by a
                //  ThrowingMethodOptimizationInfo since we should never use the optimization info
                //  after this point.
                return method.toTypeSubstitutedMethod(
                    newMethodReference,
                    builder -> {
                      if (!prototypeChanges.isEmpty()) {
                        builder
                            .apply(prototypeChanges.createParameterAnnotationsRemover(method))
                            .setGenericSignature(MethodTypeSignature.noSignature());
                      }
                    });
              });
    }

    if (!lensBuilder.isEmpty()) {
      appView.rewriteWithLens(lensBuilder.build());
    }
  }

  private GlobalReservationState computeGlobalReservationState(ExecutorService executorService)
      throws ExecutionException {
    // Tracks how many different parameter lists can be optimized into the same parameter list.
    // If only (B, A) can be rewritten into (A, B), then there is no need to rewrite parameter lists
    // on the form (B, A) into (A, B), as that won't lead to any sharing of parameter lists.
    Map<DexTypeList, Set<DexTypeList>> optimizableParameterLists = new ConcurrentHashMap<>();

    // Used to track if a given parameter list should be mapped to a specific permutation instead of
    // just sorting the parameter list. This is used to ensure that we will rewrite parameter lists
    // such as (A, B) into (B, A) if there is an unoptimizable method with parameter list (B, A).
    Map<DexTypeList, Set<DexTypeList>> reservedParameterLists = new ConcurrentHashMap<>();

    // Tracks the set of unoptimizable method signatures. These must remain as-is.
    DexMethodSignatureSet unoptimizableSignatures = DexMethodSignatureSet.createConcurrent();

    ThreadUtils.processMethods(
        appView,
        method ->
            computeReservationsFromMethod(
                method, optimizableParameterLists, reservedParameterLists, unoptimizableSignatures),
        executorService);

    // Reserve parameter lists that won't lead to any sharing after normalization. Any method with
    // such a parameter list must remain as-is.
    Set<DexTypeList> unoptimizableParameterLists = new HashSet<>();
    optimizableParameterLists.forEach(
        (sortedParameters, parameterListsBeforeNormalization) -> {
          int size = parameterListsBeforeNormalization.size();
          if (size != 1) {
            // There are multiple optimizable methods with different parameter lists that can be
            // rewritten into having the same parameter list.
            assert size > 1;
            return;
          }
          DexTypeList parameters = parameterListsBeforeNormalization.iterator().next();
          Set<DexTypeList> reservedParameters =
              reservedParameterLists.getOrDefault(sortedParameters, Collections.emptySet());
          if (!reservedParameters.isEmpty() && !reservedParameters.contains(parameters)) {
            // There is at least one optimizable method that can be rewritten into having the same
            // parameter list as an unoptimizable method.
            return;
          }
          unoptimizableParameterLists.add(parameters);
        });

    ThreadUtils.processMethods(
        appView,
        method ->
            computeExtraReservationsFromMethod(
                method, unoptimizableParameterLists, unoptimizableSignatures),
        executorService);

    return new GlobalReservationState(reservedParameterLists, unoptimizableSignatures);
  }

  private void computeReservationsFromMethod(
      ProgramMethod method,
      Map<DexTypeList, Set<DexTypeList>> optimizableParameterLists,
      Map<DexTypeList, Set<DexTypeList>> reservedParameterLists,
      DexMethodSignatureSet unoptimizableSignatures) {
    if (isUnoptimizable(method)) {
      // Record that other optimizable methods with the same set of parameter types should be
      // rewritten to have the same parameter list as this method.
      reservedParameterLists
          .computeIfAbsent(
              method.getParameters().getSorted(), ignoreKey(Sets::newConcurrentHashSet))
          .add(method.getParameters());

      // Mark signature as unoptimizable.
      unoptimizableSignatures.add(method);
    } else {
      // Record that the method's parameter list can be rewritten into any permutation.
      optimizableParameterLists
          .computeIfAbsent(
              method.getParameters().getSorted(), ignoreKey(Sets::newConcurrentHashSet))
          .add(method.getParameters());
    }
  }

  private void computeExtraReservationsFromMethod(
      ProgramMethod method,
      Set<DexTypeList> unoptimizableParameterLists,
      DexMethodSignatureSet unoptimizableSignatures) {
    if (unoptimizableParameterLists.contains(method.getParameters())) {
      unoptimizableSignatures.add(method.getMethodSignature());
    }
  }

  Map<DexMethodSignature, DexMethodSignature> computeNewInstanceInitializerSignatures(
      DexProgramClass clazz,
      LocalReservationState localReservationState,
      GlobalReservationState globalReservationState) {
    // Create a map from new method signatures to old method signatures. This produces a one-to-many
    // mapping since multiple instance initializers may normalize to the same signature.
    Map<DexMethodSignature, DexMethodSignatureSet> instanceInitializerCollisions =
        computeInstanceInitializerCollisions(clazz, localReservationState, globalReservationState);

    // Resolve each collision to ensure that the mapping is one-to-one.
    resolveInstanceInitializerCollisions(instanceInitializerCollisions);

    // Inverse the one-to-one map to produce a mapping from old method signatures to new method
    // signatures.
    return MapUtils.transform(
        instanceInitializerCollisions,
        HashMap::new,
        (newMethodSignature, methodSignatures) -> Iterables.getFirst(methodSignatures, null),
        (newMethodSignature, methodSignatures) -> newMethodSignature,
        (newMethodSignature, methodSignature, otherMethodSignature) -> {
          throw new Unreachable();
        });
  }

  private Map<DexMethodSignature, DexMethodSignatureSet> computeInstanceInitializerCollisions(
      DexProgramClass clazz,
      LocalReservationState localReservationState,
      GlobalReservationState globalReservationState) {
    Map<DexMethodSignature, DexMethodSignatureSet> instanceInitializerCollisions = new HashMap<>();
    clazz.forEachProgramInstanceInitializer(
        method -> {
          DexMethodSignature methodSignature = method.getMethodSignature();
          DexMethodSignature newMethodSignature =
              localReservationState.getNewMethodSignature(
                  methodSignature, dexItemFactory, globalReservationState);
          instanceInitializerCollisions
              .computeIfAbsent(newMethodSignature, ignoreKey(DexMethodSignatureSet::create))
              .add(methodSignature);
        });
    return instanceInitializerCollisions;
  }

  private void resolveInstanceInitializerCollisions(
      Map<DexMethodSignature, DexMethodSignatureSet> instanceInitializerCollisions) {
    WorkList<DexMethodSignature> worklist = WorkList.newEqualityWorkList();
    instanceInitializerCollisions.forEach(
        (newMethodSignature, methodSignatures) -> {
          if (methodSignatures.size() > 1) {
            worklist.addIfNotSeen(newMethodSignature);
          }
        });

    while (worklist.hasNext()) {
      DexMethodSignature newMethodSignature = worklist.removeSeen();
      DexMethodSignatureSet methodSignatures =
          instanceInitializerCollisions.get(newMethodSignature);
      assert methodSignatures.size() > 1;

      // Resolve this conflict in a deterministic way.
      DexMethodSignature survivor =
          methodSignatures.contains(newMethodSignature)
              ? newMethodSignature
              : IterableUtils.min(methodSignatures, DexMethodSignature::compareTo);

      // Disallow optimizations of all other methods than the `survivor`.
      for (DexMethodSignature methodSignature : methodSignatures) {
        if (!methodSignature.equals(survivor)) {
          DexMethodSignatureSet originalMethodSignaturesForMethodSignature =
              instanceInitializerCollisions.computeIfAbsent(
                  methodSignature, ignoreKey(DexMethodSignatureSet::create));
          originalMethodSignaturesForMethodSignature.add(methodSignature);
          if (originalMethodSignaturesForMethodSignature.size() > 1) {
            worklist.addIfNotSeen(methodSignature);
          }
        }
      }

      // Remove all pinned methods from the set of original method signatures stored at
      // instanceInitializerCollisions.get(newMethodSignature).
      methodSignatures.clear();
      methodSignatures.add(survivor);
    }
  }

  private boolean isUnoptimizable(ProgramMethod method) {
    KeepMethodInfo keepInfo = appView.getKeepInfo(method);
    if (!keepInfo.isParameterReorderingAllowed(options)
        || method.getDefinition().isLibraryMethodOverride().isPossiblyTrue()) {
      return true;
    }
    AppInfoWithLiveness appInfo = appView.appInfo();
    if (appInfo.isBootstrapMethod(method)) {
      return true;
    }
    ObjectAllocationInfoCollection objectAllocationInfoCollection =
        appInfo.getObjectAllocationInfoCollection();
    if (method.getHolder().isInterface()
        && method.getDefinition().isAbstract()
        && objectAllocationInfoCollection.isImmediateInterfaceOfInstantiatedLambda(
            method.getHolder())) {
      return true;
    }
    return false;
  }

  static class GlobalReservationState {

    // Used to track if a given parameter list should be mapped to a specific permutation instead of
    // just sorting the parameter list. This is used to ensure that we will rewrite parameter lists
    // such as (A, B) into (B, A) if there is an unoptimizable method with parameter list (B, A).
    Map<DexTypeList, DexTypeList> reservedParameters;

    // Tracks the set of unoptimizable method signatures. These must remain as-is.
    DexMethodSignatureSet unoptimizableSignatures;

    GlobalReservationState(
        Map<DexTypeList, Set<DexTypeList>> reservedParameterLists,
        DexMethodSignatureSet unoptimizableSignatures) {
      this.reservedParameters = selectDeterministicTarget(reservedParameterLists);
      this.unoptimizableSignatures = unoptimizableSignatures;
    }

    private static Map<DexTypeList, DexTypeList> selectDeterministicTarget(
        Map<DexTypeList, Set<DexTypeList>> reservedParameterLists) {
      Map<DexTypeList, DexTypeList> result = new HashMap<>();
      reservedParameterLists.forEach(
          (sortedParameters, candidates) -> {
            Iterator<DexTypeList> iterator = candidates.iterator();
            DexTypeList smallestCandidate = iterator.next();
            while (iterator.hasNext()) {
              DexTypeList candidate = iterator.next();
              if (candidate.compareTo(smallestCandidate) < 0) {
                smallestCandidate = candidate;
              }
            }
            result.put(sortedParameters, smallestCandidate);
          });
      return result;
    }

    DexTypeList getReservedParameters(DexMethodSignature methodSignature) {
      DexTypeList sortedParameters = methodSignature.getParameters().getSorted();
      return reservedParameters.getOrDefault(sortedParameters, sortedParameters);
    }

    boolean isUnoptimizable(DexMethodSignature methodSignature) {
      return unoptimizableSignatures.contains(methodSignature);
    }
  }

  static class LocalReservationState {

    MutableBidirectionalOneToOneMap<DexMethodSignature, DexMethodSignature> newMethodSignatures =
        new BidirectionalOneToOneHashMap<>();

    DexMethodSignature getNewMethodSignature(
        DexMethodSignature methodSignature,
        DexItemFactory dexItemFactory,
        GlobalReservationState globalReservationState) {
      return internalGetAndReserveNewMethodSignature(
          methodSignature, dexItemFactory, globalReservationState, false);
    }

    DexMethodSignature getAndReserveNewMethodSignature(
        DexMethodSignature methodSignature,
        DexItemFactory dexItemFactory,
        GlobalReservationState globalReservationState) {
      return internalGetAndReserveNewMethodSignature(
          methodSignature, dexItemFactory, globalReservationState, true);
    }

    private DexMethodSignature internalGetAndReserveNewMethodSignature(
        DexMethodSignature methodSignature,
        DexItemFactory dexItemFactory,
        GlobalReservationState globalReservationState,
        boolean reserve) {
      if (globalReservationState.isUnoptimizable(methodSignature)) {
        assert !newMethodSignatures.containsKey(methodSignature);
        return methodSignature;
      }
      DexMethodSignature reservedSignature = newMethodSignatures.get(methodSignature);
      if (reservedSignature != null) {
        assert reservedSignature
            .getParameters()
            .equals(globalReservationState.getReservedParameters(methodSignature));
        return reservedSignature;
      }
      DexTypeList reservedParameters =
          globalReservationState.getReservedParameters(methodSignature);
      DexMethodSignature newMethodSignature =
          methodSignature.withParameters(reservedParameters, dexItemFactory);
      if (newMethodSignatures.containsValue(newMethodSignature)) {
        int index = 1;
        String newMethodBaseName = methodSignature.getName().toString();
        do {
          DexString newMethodName = dexItemFactory.createString(newMethodBaseName + "$" + index);
          newMethodSignature = newMethodSignature.withName(newMethodName);
          index++;
        } while (newMethodSignatures.containsValue(newMethodSignature));
      }
      if (reserve) {
        newMethodSignatures.put(methodSignature, newMethodSignature);
      }
      return newMethodSignature;
    }
  }
}