// 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.code.ConstInstruction;
import com.android.tools.r8.ir.code.IRCode;
import com.android.tools.r8.ir.code.Position;
import com.android.tools.r8.shaking.AppInfoWithLiveness;
import com.android.tools.r8.utils.BooleanUtils;
import com.google.common.collect.Ordering;
import it.unimi.dsi.fastutil.ints.Int2ReferenceRBTreeMap;
import it.unimi.dsi.fastutil.ints.Int2ReferenceSortedMap;
import it.unimi.dsi.fastutil.ints.IntBidirectionalIterator;
import java.util.function.Consumer;

public class RewrittenPrototypeDescription {

  public interface ArgumentInfo {

    @SuppressWarnings("ConstantConditions")
    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);
    }

    ArgumentInfo NO_INFO =
        info -> {
          assert false : "ArgumentInfo NO_INFO should not be combined";
          return info;
        };

    default boolean isRemovedArgumentInfo() {
      return false;
    }

    default RemovedArgumentInfo asRemovedArgumentInfo() {
      return null;
    }

    default boolean isRewrittenTypeInfo() {
      return false;
    }

    default RewrittenTypeInfo asRewrittenTypeInfo() {
      return null;
    }

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

  public static class RemovedArgumentInfo implements ArgumentInfo {

    public static class Builder {

      private boolean isAlwaysNull = false;
      private DexType type = null;

      public Builder setIsAlwaysNull() {
        this.isAlwaysNull = true;
        return this;
      }

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

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

    private final boolean isAlwaysNull;
    private final DexType type;

    private RemovedArgumentInfo(boolean isAlwaysNull, DexType type) {
      this.isAlwaysNull = isAlwaysNull;
      this.type = type;
    }

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

    public DexType getType() {
      return type;
    }

    public boolean isAlwaysNull() {
      return isAlwaysNull;
    }

    public boolean isNeverUsed() {
      return !isAlwaysNull;
    }

    @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;
    }
  }

  public static class RewrittenTypeInfo implements ArgumentInfo {

    private final DexType oldType;
    private final DexType newType;

    static RewrittenTypeInfo toVoid(DexType oldReturnType, AppView<?> appView) {
      return new RewrittenTypeInfo(oldReturnType, appView.dexItemFactory().voidType);
    }

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

    public DexType getNewType() {
      return newType;
    }

    public DexType getOldType() {
      return oldType;
    }

    boolean hasBeenChangedToReturnVoid(AppView<?> appView) {
      return newType == appView.dexItemFactory().voidType;
    }

    @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();
      RewrittenTypeInfo rewrittenTypeInfo = info.asRewrittenTypeInfo();
      assert newType == rewrittenTypeInfo.oldType;
      return new RewrittenTypeInfo(oldType, rewrittenTypeInfo.newType);
    }
  }

  public static class ArgumentInfoCollection {

    private static final ArgumentInfoCollection EMPTY = new ArgumentInfoCollection();

    private final Int2ReferenceSortedMap<ArgumentInfo> argumentInfos;

    // Specific constructor for empty.
    private ArgumentInfoCollection() {
      this.argumentInfos = new Int2ReferenceRBTreeMap<>();
    }

    private ArgumentInfoCollection(Int2ReferenceSortedMap<ArgumentInfo> argumentInfos) {
      assert argumentInfos != null : "should use empty.";
      assert !argumentInfos.isEmpty() : "should use empty.";
      this.argumentInfos = argumentInfos;
    }

    public static ArgumentInfoCollection empty() {
      return EMPTY;
    }

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

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

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

    public static class Builder {

      private Int2ReferenceSortedMap<ArgumentInfo> argumentInfos;

      public void addArgumentInfo(int argIndex, ArgumentInfo argInfo) {
        if (argumentInfos == null) {
          argumentInfos = new Int2ReferenceRBTreeMap<>();
        }
        assert !argumentInfos.containsKey(argIndex);
        argumentInfos.put(argIndex, argInfo);
      }

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

    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.method.proto.parameters.values;
      if (isEmpty()) {
        return params;
      }
      DexType[] newParams = new DexType[params.length - numberOfRemovedArguments()];
      int offset = encodedMethod.isStatic() ? 0 : 1;
      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;
        }
      }

      Int2ReferenceSortedMap<ArgumentInfo> newArgInfos = new Int2ReferenceRBTreeMap<>();
      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 Consumer<DexEncodedMethod.Builder> createParameterAnnotationsRemover(
        DexEncodedMethod method) {
      if (numberOfRemovedArguments() > 0 && !method.parameterAnnotationsList.isEmpty()) {
        return builder -> {
          int firstArgumentIndex = BooleanUtils.intValue(!method.isStatic());
          builder.removeParameterAnnotations(
              oldIndex -> getArgumentInfo(oldIndex + firstArgumentIndex).isRemovedArgumentInfo());
        };
      }
      return null;
    }
  }

  private static final RewrittenPrototypeDescription none = new RewrittenPrototypeDescription();

  private final boolean extraNullParameter;
  private final ArgumentInfoCollection argumentInfoCollection;
  private final RewrittenTypeInfo rewrittenReturnInfo;

  private RewrittenPrototypeDescription() {
    this(false, null, ArgumentInfoCollection.empty());
  }

  private RewrittenPrototypeDescription(
      boolean extraNullParameter,
      RewrittenTypeInfo rewrittenReturnInfo,
      ArgumentInfoCollection argumentsInfo) {
    assert argumentsInfo != null;
    this.extraNullParameter = extraNullParameter;
    this.rewrittenReturnInfo = rewrittenReturnInfo;
    this.argumentInfoCollection = argumentsInfo;
  }

  public static RewrittenPrototypeDescription createForUninstantiatedTypes(
      DexMethod method,
      AppView<AppInfoWithLiveness> appView,
      ArgumentInfoCollection removedArgumentsInfo) {
    DexType returnType = method.proto.returnType;
    RewrittenTypeInfo returnInfo =
        returnType.isAlwaysNull(appView) ? RewrittenTypeInfo.toVoid(returnType, appView) : null;
    return new RewrittenPrototypeDescription(false, returnInfo, removedArgumentsInfo);
  }

  public static RewrittenPrototypeDescription createForRewrittenTypes(
      RewrittenTypeInfo returnInfo, ArgumentInfoCollection rewrittenArgumentsInfo) {
    return new RewrittenPrototypeDescription(false, returnInfo, rewrittenArgumentsInfo);
  }

  public static RewrittenPrototypeDescription none() {
    return none;
  }

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

  public boolean hasExtraNullParameter() {
    return extraNullParameter;
  }

  public boolean hasBeenChangedToReturnVoid(AppView<?> appView) {
    return rewrittenReturnInfo != null && rewrittenReturnInfo.hasBeenChangedToReturnVoid(appView);
  }

  public ArgumentInfoCollection getArgumentInfoCollection() {
    return argumentInfoCollection;
  }

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

  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 ConstInstruction getConstantReturn(IRCode code, Position position) {
    ConstInstruction instruction = code.createConstNull();
    instruction.setPosition(position);
    return instruction;
  }

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

  public RewrittenPrototypeDescription withConstantReturn(
      DexType oldReturnType, AppView<?> appView) {
    assert rewrittenReturnInfo == null;
    return !hasBeenChangedToReturnVoid(appView)
        ? new RewrittenPrototypeDescription(
            extraNullParameter,
            RewrittenTypeInfo.toVoid(oldReturnType, appView),
            argumentInfoCollection)
        : this;
  }

  public RewrittenPrototypeDescription withRemovedArguments(ArgumentInfoCollection other) {
    return new RewrittenPrototypeDescription(
        extraNullParameter, rewrittenReturnInfo, argumentInfoCollection.combine(other));
  }

  public RewrittenPrototypeDescription withExtraNullParameter() {
    return !extraNullParameter
        ? new RewrittenPrototypeDescription(true, rewrittenReturnInfo, argumentInfoCollection)
        : this;
  }
}