// 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.graph;

import com.android.tools.r8.ir.analysis.value.SingleValue;
import com.android.tools.r8.ir.code.ConstInstruction;
import com.android.tools.r8.ir.code.IRCode;
import com.android.tools.r8.ir.code.Instruction;
import com.android.tools.r8.ir.code.Position;
import com.android.tools.r8.ir.code.TypeAndLocalInfoSupplier;
import com.android.tools.r8.ir.conversion.ExtraParameter;
import com.android.tools.r8.ir.conversion.ExtraUnusedNullParameter;
import com.android.tools.r8.ir.optimize.info.MethodOptimizationInfoFixer;
import com.android.tools.r8.shaking.AppInfoWithLiveness;
import com.android.tools.r8.utils.ConsumerUtils;
import com.android.tools.r8.utils.IntObjConsumer;
import com.android.tools.r8.utils.IteratorUtils;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Ordering;
import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectMap.Entry;
import it.unimi.dsi.fastutil.ints.Int2ObjectRBTreeMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectSortedMap;
import it.unimi.dsi.fastutil.ints.IntArrayList;
import it.unimi.dsi.fastutil.ints.IntBidirectionalIterator;
import it.unimi.dsi.fastutil.ints.IntCollection;
import it.unimi.dsi.fastutil.ints.IntList;
import it.unimi.dsi.fastutil.ints.IntLists;
import it.unimi.dsi.fastutil.ints.IntSortedSet;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import java.util.function.Consumer;

public class RewrittenPrototypeDescription {

  public abstract static class ArgumentInfo {

    static final ArgumentInfo NO_INFO =
        new ArgumentInfo() {

          @Override
          public ArgumentInfo combine(ArgumentInfo info) {
            assert false : "ArgumentInfo NO_INFO should not be combined";
            return info;
          }

          @Override
          public ArgumentInfo rewrittenWithLens(
              AppView<AppInfoWithLiveness> appView, GraphLens graphLens) {
            return this;
          }

          @Override
          public boolean equals(Object obj) {
            return obj == this;
          }

          @Override
          public int hashCode() {
            return System.identityHashCode(this);
          }
        };

    @SuppressWarnings("ConstantConditions")
    public static ArgumentInfo combine(ArgumentInfo arg1, ArgumentInfo arg2) {
      if (arg1 == null) {
        assert arg2 != null;
        return arg2;
      }
      if (arg2 == null) {
        assert arg1 != null;
        return arg1;
      }
      return arg1.combine(arg2);
    }

    public boolean isRemovedArgumentInfo() {
      return false;
    }

    public RemovedArgumentInfo asRemovedArgumentInfo() {
      return null;
    }

    public boolean isRewrittenTypeInfo() {
      return false;
    }

    public RewrittenTypeInfo asRewrittenTypeInfo() {
      return null;
    }

    // ArgumentInfo are combined with `this` first, and the `info` argument second.
    public abstract ArgumentInfo combine(ArgumentInfo info);

    public abstract ArgumentInfo rewrittenWithLens(
        AppView<AppInfoWithLiveness> appView, GraphLens graphLens);

    @Override
    public abstract boolean equals(Object obj);

    @Override
    public abstract int hashCode();
  }

  public static class RemovedArgumentInfo extends ArgumentInfo {

    public static class Builder {

      private SingleValue singleValue;
      private DexType type;

      public Builder setSingleValue(SingleValue singleValue) {
        this.singleValue = singleValue;
        return this;
      }

      public Builder setType(DexType type) {
        this.type = type;
        return this;
      }

      public RemovedArgumentInfo build() {
        assert type != null;
        return new RemovedArgumentInfo(singleValue, type);
      }
    }

    private final SingleValue singleValue;
    private final DexType type;

    private RemovedArgumentInfo(SingleValue singleValue, DexType type) {
      this.singleValue = singleValue;
      this.type = type;
    }

    public static Builder builder() {
      return new Builder();
    }

    public boolean hasSingleValue() {
      return singleValue != null;
    }

    public SingleValue getSingleValue() {
      return singleValue;
    }

    public DexType getType() {
      return type;
    }

    public boolean isNeverUsed() {
      return !hasSingleValue();
    }

    @Override
    public boolean isRemovedArgumentInfo() {
      return true;
    }

    @Override
    public RemovedArgumentInfo asRemovedArgumentInfo() {
      return this;
    }

    @Override
    public ArgumentInfo combine(ArgumentInfo info) {
      assert false : "Once the argument is removed one cannot modify it any further.";
      return this;
    }

    @Override
    public RemovedArgumentInfo rewrittenWithLens(
        AppView<AppInfoWithLiveness> appView, GraphLens graphLens) {
      SingleValue rewrittenSingleValue =
          hasSingleValue() ? singleValue.rewrittenWithLens(appView, graphLens) : null;
      DexType rewrittenType = graphLens.lookupType(type);
      if (rewrittenSingleValue != singleValue || rewrittenType != type) {
        return new RemovedArgumentInfo(rewrittenSingleValue, rewrittenType);
      }
      return this;
    }

    @Override
    public boolean equals(Object obj) {
      if (obj == null || getClass() != obj.getClass()) {
        return false;
      }
      RemovedArgumentInfo other = (RemovedArgumentInfo) obj;
      return type == other.type && Objects.equals(singleValue, other.singleValue);
    }

    @Override
    public int hashCode() {
      return Objects.hash(singleValue, type);
    }
  }

  public static class RewrittenTypeInfo extends ArgumentInfo {

    private final DexType castType;
    private final DexType oldType;
    private final DexType newType;
    private final SingleValue singleValue;

    public static Builder builder() {
      return new Builder();
    }

    public static RewrittenTypeInfo toVoid(
        DexType oldReturnType, DexItemFactory dexItemFactory, SingleValue singleValue) {
      assert singleValue != null;
      return new RewrittenTypeInfo(oldReturnType, dexItemFactory.voidType, null, singleValue);
    }

    public RewrittenTypeInfo(DexType oldType, DexType newType) {
      this(oldType, newType, null, null);
    }

    public RewrittenTypeInfo(
        DexType oldType, DexType newType, DexType castType, SingleValue singleValue) {
      this.castType = castType;
      this.oldType = oldType;
      this.newType = newType;
      this.singleValue = singleValue;
      assert !newType.isVoidType() || singleValue != null;
    }

    public RewrittenTypeInfo combine(RewrittenPrototypeDescription other) {
      return other.hasRewrittenReturnInfo() ? combine(other.getRewrittenReturnInfo()) : this;
    }

    public DexType getCastType() {
      return castType;
    }

    public DexType getNewType() {
      return newType;
    }

    public DexType getOldType() {
      return oldType;
    }

    public SingleValue getSingleValue() {
      return singleValue;
    }

    boolean hasBeenChangedToReturnVoid() {
      return newType.isVoidType();
    }

    public boolean hasCastType() {
      return castType != null;
    }

    public boolean hasSingleValue() {
      return singleValue != null;
    }

    @Override
    public boolean isRewrittenTypeInfo() {
      return true;
    }

    @Override
    public RewrittenTypeInfo asRewrittenTypeInfo() {
      return this;
    }

    @Override
    public ArgumentInfo combine(ArgumentInfo info) {
      if (info.isRemovedArgumentInfo()) {
        return info;
      }
      assert info.isRewrittenTypeInfo();
      return combine(info.asRewrittenTypeInfo());
    }

    public RewrittenTypeInfo combine(RewrittenTypeInfo other) {
      assert !getNewType().isVoidType();
      assert getNewType() == other.getOldType();
      return new RewrittenTypeInfo(
          getOldType(), other.getNewType(), getCastType(), other.getSingleValue());
    }

    @Override
    public RewrittenTypeInfo rewrittenWithLens(
        AppView<AppInfoWithLiveness> appView, GraphLens graphLens) {
      DexType rewrittenCastType = castType != null ? graphLens.lookupType(castType) : null;
      DexType rewrittenNewType = graphLens.lookupType(newType);
      SingleValue rewrittenSingleValue =
          hasSingleValue() ? getSingleValue().rewrittenWithLens(appView, graphLens) : null;
      if (rewrittenCastType != castType
          || rewrittenNewType != newType
          || rewrittenSingleValue != singleValue) {
        // The old type is intentionally not rewritten.
        return new RewrittenTypeInfo(
            oldType, rewrittenNewType, rewrittenCastType, rewrittenSingleValue);
      }
      return this;
    }

    @Override
    public boolean equals(Object obj) {
      if (obj == null || getClass() != obj.getClass()) {
        return false;
      }
      RewrittenTypeInfo other = (RewrittenTypeInfo) obj;
      return oldType == other.oldType
          && newType == other.newType
          && Objects.equals(singleValue, other.singleValue);
    }

    @Override
    public int hashCode() {
      return Objects.hash(oldType, newType, singleValue);
    }

    public boolean verifyIsDueToUnboxing(DexItemFactory dexItemFactory) {
      assert oldType.toBaseType(dexItemFactory).isClassType();
      assert newType.toBaseType(dexItemFactory).isIntType();
      return true;
    }

    public static class Builder {

      private DexType castType;
      private DexType oldType;
      private DexType newType;
      private SingleValue singleValue;

      public Builder setCastType(DexType castType) {
        this.castType = castType;
        return this;
      }

      public Builder setOldType(DexType oldType) {
        this.oldType = oldType;
        return this;
      }

      public Builder setNewType(DexType newType) {
        this.newType = newType;
        return this;
      }

      public Builder setSingleValue(SingleValue singleValue) {
        this.singleValue = singleValue;
        return this;
      }

      public RewrittenTypeInfo build() {
        return new RewrittenTypeInfo(oldType, newType, castType, singleValue);
      }
    }
  }

  public static class ArgumentInfoCollection {

    private static final ArgumentInfoCollection EMPTY = new ArgumentInfoCollection();

    private final Int2ObjectSortedMap<ArgumentInfo> argumentInfos;

    // Specific constructor for empty.
    private ArgumentInfoCollection() {
      this.argumentInfos = new Int2ObjectRBTreeMap<>();
    }

    private ArgumentInfoCollection(Int2ObjectSortedMap<ArgumentInfo> argumentInfos) {
      assert argumentInfos != null : "should use empty.";
      assert !argumentInfos.isEmpty() : "should use empty.";
      this.argumentInfos = argumentInfos;
    }

    public static ArgumentInfoCollection empty() {
      return EMPTY;
    }

    public void forEach(IntObjConsumer<ArgumentInfo> consumer) {
      for (Entry<ArgumentInfo> entry : argumentInfos.int2ObjectEntrySet()) {
        consumer.accept(entry.getIntKey(), entry.getValue());
      }
    }

    public IntSortedSet getKeys() {
      return argumentInfos.keySet();
    }

    public IntCollection getRemovedParameterIndices() {
      int numberOfRemovedArguments = numberOfRemovedArguments();
      if (numberOfRemovedArguments == 0) {
        return IntLists.EMPTY_LIST;
      }
      if (numberOfRemovedArguments == argumentInfos.size()) {
        return getKeys();
      }
      IntList removedParameterIndices = new IntArrayList(numberOfRemovedArguments);
      Iterator<Entry<ArgumentInfo>> iterator = iterator();
      while (iterator.hasNext()) {
        Entry<ArgumentInfo> entry = iterator.next();
        if (entry.getValue().isRemovedArgumentInfo()) {
          removedParameterIndices.add(entry.getIntKey());
        }
      }
      return removedParameterIndices;
    }

    public boolean isArgumentRemoved(int argumentIndex) {
      return getArgumentInfo(argumentIndex).isRemovedArgumentInfo();
    }

    public boolean isEmpty() {
      return this == EMPTY;
    }

    public Iterator<Entry<ArgumentInfo>> iterator() {
      return argumentInfos.int2ObjectEntrySet().iterator();
    }

    public boolean hasRemovedArguments() {
      for (ArgumentInfo value : argumentInfos.values()) {
        if (value.isRemovedArgumentInfo()) {
          return true;
        }
      }
      return false;
    }

    public int numberOfRemovedArguments() {
      int removed = 0;
      for (ArgumentInfo value : argumentInfos.values()) {
        if (value.isRemovedArgumentInfo()) {
          removed++;
        }
      }
      return removed;
    }

    public boolean hasArgumentInfo(int argumentIndex) {
      return argumentInfos.containsKey(argumentIndex);
    }

    public ArgumentInfo getArgumentInfo(int argumentIndex) {
      return argumentInfos.getOrDefault(argumentIndex, ArgumentInfo.NO_INFO);
    }

    public int size() {
      return argumentInfos.size();
    }

    public ArgumentInfoCollection rewrittenWithLens(
        AppView<AppInfoWithLiveness> appView, GraphLens graphLens) {
      Int2ObjectSortedMap<ArgumentInfo> rewrittenArgumentInfos = new Int2ObjectRBTreeMap<>();
      for (Int2ObjectMap.Entry<ArgumentInfo> entry : argumentInfos.int2ObjectEntrySet()) {
        ArgumentInfo argumentInfo = entry.getValue();
        ArgumentInfo rewrittenArgumentInfo = argumentInfo.rewrittenWithLens(appView, graphLens);
        if (rewrittenArgumentInfo != argumentInfo) {
          rewrittenArgumentInfos.put(entry.getIntKey(), rewrittenArgumentInfo);
        }
      }
      if (!rewrittenArgumentInfos.isEmpty()) {
        for (Int2ObjectMap.Entry<ArgumentInfo> entry : argumentInfos.int2ObjectEntrySet()) {
          int key = entry.getIntKey();
          if (!rewrittenArgumentInfos.containsKey(key)) {
            rewrittenArgumentInfos.put(key, entry.getValue());
          }
        }
        return new ArgumentInfoCollection(rewrittenArgumentInfos);
      }
      return this;
    }

    @Override
    public boolean equals(Object obj) {
      if (obj == null || getClass() != obj.getClass()) {
        return false;
      }
      ArgumentInfoCollection other = (ArgumentInfoCollection) obj;
      return argumentInfos.equals(other.argumentInfos);
    }

    @Override
    public int hashCode() {
      return argumentInfos.hashCode();
    }

    public static Builder builder() {
      return new Builder();
    }

    public static class Builder {

      private Int2ObjectSortedMap<ArgumentInfo> argumentInfos;

      public Builder addArgumentInfo(int argIndex, ArgumentInfo argInfo) {
        if (argumentInfos == null) {
          argumentInfos = new Int2ObjectRBTreeMap<>();
        }
        assert !argumentInfos.containsKey(argIndex);
        argumentInfos.put(argIndex, argInfo);
        return this;
      }

      public ArgumentInfoCollection build() {
        if (argumentInfos == null || argumentInfos.isEmpty()) {
          return EMPTY;
        }
        return new ArgumentInfoCollection(argumentInfos);
      }
    }

    public DexMethod rewriteMethod(ProgramMethod method, DexItemFactory dexItemFactory) {
      if (isEmpty()) {
        return method.getReference();
      }
      DexProto rewrittenProto = rewriteProto(method, dexItemFactory);
      return method.getReference().withProto(rewrittenProto, dexItemFactory);
    }

    public DexProto rewriteProto(ProgramMethod method, DexItemFactory dexItemFactory) {
      return isEmpty()
          ? method.getProto()
          : dexItemFactory.createProto(method.getReturnType(), rewriteParameters(method));
    }

    public DexType[] rewriteParameters(ProgramMethod method) {
      return rewriteParameters(method.getDefinition());
    }

    public DexType[] rewriteParameters(DexEncodedMethod encodedMethod) {
      // Currently not allowed to remove the receiver of an instance method. This would involve
      // changing invoke-direct/invoke-virtual into invoke-static.
      assert encodedMethod.isStatic() || !getArgumentInfo(0).isRemovedArgumentInfo();
      DexType[] params = encodedMethod.getReference().proto.parameters.values;
      if (isEmpty()) {
        return params;
      }
      DexType[] newParams = new DexType[params.length - numberOfRemovedArguments()];
      int offset = encodedMethod.getFirstNonReceiverArgumentIndex();
      int newParamIndex = 0;
      for (int oldParamIndex = 0; oldParamIndex < params.length; oldParamIndex++) {
        ArgumentInfo argInfo = argumentInfos.get(oldParamIndex + offset);
        if (argInfo == null) {
          newParams[newParamIndex++] = params[oldParamIndex];
        } else if (argInfo.isRewrittenTypeInfo()) {
          RewrittenTypeInfo rewrittenTypeInfo = argInfo.asRewrittenTypeInfo();
          assert params[oldParamIndex] == rewrittenTypeInfo.oldType;
          newParams[newParamIndex++] = rewrittenTypeInfo.newType;
        }
      }
      return newParams;
    }

    public ArgumentInfoCollection combine(ArgumentInfoCollection info) {
      if (isEmpty()) {
        return info;
      } else {
        if (info.isEmpty()) {
          return this;
        }
      }

      Int2ObjectSortedMap<ArgumentInfo> newArgInfos = new Int2ObjectRBTreeMap<>();
      newArgInfos.putAll(argumentInfos);
      IntBidirectionalIterator iterator = argumentInfos.keySet().iterator();
      int offset = 0;
      int nextArgIndex;
      for (int pendingArgIndex : info.argumentInfos.keySet()) {
        nextArgIndex = peekNextOrMax(iterator);
        while (nextArgIndex <= pendingArgIndex + offset) {
          iterator.nextInt();
          ArgumentInfo argumentInfo = argumentInfos.get(nextArgIndex);
          nextArgIndex = peekNextOrMax(iterator);
          if (argumentInfo.isRemovedArgumentInfo()) {
            offset++;
          }
        }
        ArgumentInfo newArgInfo =
            nextArgIndex == pendingArgIndex + offset
                ? ArgumentInfo.combine(
                    argumentInfos.get(nextArgIndex), info.argumentInfos.get(pendingArgIndex))
                : info.argumentInfos.get(pendingArgIndex);
        newArgInfos.put(pendingArgIndex + offset, newArgInfo);
      }
      assert Ordering.natural().isOrdered(newArgInfos.keySet());
      return new ArgumentInfoCollection(newArgInfos);
    }

    static int peekNextOrMax(IntBidirectionalIterator iterator) {
      if (iterator.hasNext()) {
        int i = iterator.nextInt();
        iterator.previousInt();
        return i;
      }
      return Integer.MAX_VALUE;
    }

    public MethodOptimizationInfoFixer createMethodOptimizationInfoFixer() {
      RewrittenPrototypeDescription prototypeChanges =
          RewrittenPrototypeDescription.create(Collections.emptyList(), null, this);
      return prototypeChanges.createMethodOptimizationInfoFixer();
    }

    /**
     * Returns a function for rewriting the parameter annotations on a method info after prototype
     * changes were made.
     */
    public Consumer<DexEncodedMethod.Builder> createParameterAnnotationsRemover(
        DexEncodedMethod method) {
      if (numberOfRemovedArguments() > 0 && !method.parameterAnnotationsList.isEmpty()) {
        return builder -> {
          int firstArgumentIndex = method.getFirstNonReceiverArgumentIndex();
          builder.removeParameterAnnotations(
              oldIndex -> getArgumentInfo(oldIndex + firstArgumentIndex).isRemovedArgumentInfo());
        };
      }
      return ConsumerUtils.emptyConsumer();
    }

    public int getNewArgumentIndex(int argumentIndex) {
      int numberOfArgumentsRemovedBeforeArgument = 0;
      Iterator<Entry<ArgumentInfo>> iterator = iterator();
      while (iterator.hasNext()) {
        Entry<ArgumentInfo> entry = iterator.next();
        int argumentIndexForInfo = entry.getIntKey();
        if (argumentIndexForInfo >= argumentIndex) {
          break;
        }
        ArgumentInfo argumentInfo = entry.getValue();
        if (argumentInfo.isRemovedArgumentInfo()) {
          numberOfArgumentsRemovedBeforeArgument++;
        }
      }
      assert IteratorUtils.allRemainingMatchDestructive(
          iterator, entry -> entry.getIntKey() >= argumentIndex);
      return argumentIndex - numberOfArgumentsRemovedBeforeArgument;
    }
  }

  private static final RewrittenPrototypeDescription NONE = new RewrittenPrototypeDescription();

  private final List<ExtraParameter> extraParameters;
  private final ArgumentInfoCollection argumentInfoCollection;
  private final RewrittenTypeInfo rewrittenReturnInfo;

  private RewrittenPrototypeDescription() {
    this.extraParameters = Collections.emptyList();
    this.rewrittenReturnInfo = null;
    this.argumentInfoCollection = ArgumentInfoCollection.empty();
  }

  private RewrittenPrototypeDescription(
      List<ExtraParameter> extraParameters,
      RewrittenTypeInfo rewrittenReturnInfo,
      ArgumentInfoCollection argumentsInfo) {
    assert argumentsInfo != null;
    this.extraParameters = extraParameters;
    this.rewrittenReturnInfo = rewrittenReturnInfo;
    this.argumentInfoCollection = argumentsInfo;
    assert !isEmpty();
  }

  public static RewrittenPrototypeDescription create(
      List<ExtraParameter> extraParameters,
      RewrittenTypeInfo rewrittenReturnInfo,
      ArgumentInfoCollection argumentsInfo) {
    return extraParameters.isEmpty() && rewrittenReturnInfo == null && argumentsInfo.isEmpty()
        ? none()
        : new RewrittenPrototypeDescription(extraParameters, rewrittenReturnInfo, argumentsInfo);
  }

  public static RewrittenPrototypeDescription createForRewrittenTypes(
      RewrittenTypeInfo returnInfo, ArgumentInfoCollection rewrittenArgumentsInfo) {
    return create(Collections.emptyList(), returnInfo, rewrittenArgumentsInfo);
  }

  public static RewrittenPrototypeDescription none() {
    return NONE;
  }

  public Consumer<DexEncodedMethod.Builder> createParameterAnnotationsRemover(
      DexEncodedMethod method) {
    return getArgumentInfoCollection().createParameterAnnotationsRemover(method);
  }

  public MethodOptimizationInfoFixer createMethodOptimizationInfoFixer() {
    return new RewrittenPrototypeDescriptionMethodOptimizationInfoFixer(this);
  }

  public RewrittenPrototypeDescription combine(RewrittenPrototypeDescription other) {
    if (isEmpty()) {
      return other;
    }
    if (other.isEmpty()) {
      return this;
    }
    // We currently don't have any passes that remove extra parameters inserted by previous passes.
    // If the input prototype changes have removed some of the extra parameters, we would need to
    // adapt the merging of prototype changes below.
    List<ExtraParameter> newExtraParameters =
        ImmutableList.<ExtraParameter>builder()
            .addAll(getExtraParameters())
            .addAll(other.getExtraParameters())
            .build();
    RewrittenTypeInfo newRewrittenTypeInfo =
        hasRewrittenReturnInfo()
            ? getRewrittenReturnInfo().combine(other)
            : other.getRewrittenReturnInfo();
    ArgumentInfoCollection newArgumentInfoCollection =
        getArgumentInfoCollection().combine(other.getArgumentInfoCollection());
    return new RewrittenPrototypeDescription(
        newExtraParameters, newRewrittenTypeInfo, newArgumentInfoCollection);
  }

  public boolean isEmpty() {
    return extraParameters.isEmpty()
        && rewrittenReturnInfo == null
        && argumentInfoCollection.isEmpty();
  }

  public boolean hasExtraParameters() {
    return !extraParameters.isEmpty();
  }

  public List<ExtraParameter> getExtraParameters() {
    return extraParameters;
  }

  public int numberOfExtraParameters() {
    return extraParameters.size();
  }

  public boolean hasBeenChangedToReturnVoid() {
    return rewrittenReturnInfo != null && rewrittenReturnInfo.hasBeenChangedToReturnVoid();
  }

  public ArgumentInfoCollection getArgumentInfoCollection() {
    return argumentInfoCollection;
  }

  public boolean hasRewrittenReturnInfo() {
    return rewrittenReturnInfo != null;
  }

  public boolean requiresRewritingAtCallSite() {
    return hasRewrittenReturnInfo()
        || numberOfExtraParameters() > 0
        || argumentInfoCollection.numberOfRemovedArguments() > 0;
  }

  public RewrittenTypeInfo getRewrittenReturnInfo() {
    return rewrittenReturnInfo;
  }

  /**
   * Returns the {@link ConstInstruction} that should be used to materialize the result of
   * invocations to the method represented by this {@link RewrittenPrototypeDescription}.
   *
   * <p>This method should only be used for methods that return a constant value and whose return
   * type has been changed to void.
   *
   * <p>Note that the current implementation always returns null at this point.
   */
  public Instruction getConstantReturn(
      AppView<AppInfoWithLiveness> appView,
      IRCode code,
      ProgramMethod method,
      Position position,
      TypeAndLocalInfoSupplier info) {
    assert rewrittenReturnInfo != null;
    assert rewrittenReturnInfo.hasSingleValue();
    assert rewrittenReturnInfo.getSingleValue().isMaterializableInContext(appView, method);
    Instruction instruction =
        rewrittenReturnInfo.getSingleValue().createMaterializingInstruction(appView, code, info);
    instruction.setPosition(position);
    return instruction;
  }

  public DexMethod rewriteMethod(ProgramMethod method, DexItemFactory dexItemFactory) {
    if (isEmpty()) {
      return method.getReference();
    }
    DexProto rewrittenProto = rewriteProto(method.getDefinition(), dexItemFactory);
    return method.getReference().withProto(rewrittenProto, dexItemFactory);
  }

  public DexProto rewriteProto(DexEncodedMethod encodedMethod, DexItemFactory dexItemFactory) {
    if (isEmpty()) {
      return encodedMethod.getReference().proto;
    }
    DexType newReturnType =
        rewrittenReturnInfo != null
            ? rewrittenReturnInfo.newType
            : encodedMethod.getReference().proto.returnType;
    DexType[] newParameters = argumentInfoCollection.rewriteParameters(encodedMethod);
    return dexItemFactory.createProto(newReturnType, newParameters);
  }

  public RewrittenPrototypeDescription rewrittenWithLens(
      AppView<AppInfoWithLiveness> appView, GraphLens graphLens) {
    ArgumentInfoCollection newArgumentInfoCollection =
        argumentInfoCollection.rewrittenWithLens(appView, graphLens);
    RewrittenTypeInfo newRewrittenReturnInfo =
        hasRewrittenReturnInfo() ? rewrittenReturnInfo.rewrittenWithLens(appView, graphLens) : null;
    if (newArgumentInfoCollection != argumentInfoCollection
        || newRewrittenReturnInfo != rewrittenReturnInfo) {
      return new RewrittenPrototypeDescription(
          extraParameters, newRewrittenReturnInfo, newArgumentInfoCollection);
    }
    return this;
  }

  public RewrittenPrototypeDescription withRewrittenReturnInfo(
      RewrittenTypeInfo newRewrittenReturnInfo) {
    if (Objects.equals(rewrittenReturnInfo, newRewrittenReturnInfo)) {
      return this;
    }
    return new RewrittenPrototypeDescription(
        extraParameters, newRewrittenReturnInfo, argumentInfoCollection);
  }

  public RewrittenPrototypeDescription withExtraUnusedNullParameters(
      int numberOfExtraUnusedNullParameters) {
    List<ExtraParameter> parameters =
        Collections.nCopies(numberOfExtraUnusedNullParameters, new ExtraUnusedNullParameter());
    return withExtraParameters(parameters);
  }

  public RewrittenPrototypeDescription withExtraParameters(List<ExtraParameter> parameters) {
    if (parameters.isEmpty()) {
      return this;
    }
    List<ExtraParameter> newExtraParameters =
        new ArrayList<>(extraParameters.size() + parameters.size());
    newExtraParameters.addAll(extraParameters);
    newExtraParameters.addAll(parameters);
    return new RewrittenPrototypeDescription(
        newExtraParameters, rewrittenReturnInfo, argumentInfoCollection);
  }

  @Override
  public boolean equals(Object obj) {
    if (obj == null || getClass() != obj.getClass()) {
      return false;
    }
    RewrittenPrototypeDescription other = (RewrittenPrototypeDescription) obj;
    return extraParameters.equals(other.extraParameters)
        && Objects.equals(rewrittenReturnInfo, other.rewrittenReturnInfo)
        && argumentInfoCollection.equals(other.argumentInfoCollection);
  }

  @Override
  public int hashCode() {
    return Objects.hash(extraParameters, rewrittenReturnInfo, argumentInfoCollection);
  }
}