// Copyright (c) 2017, 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.ir.desugar;

import com.android.tools.r8.errors.CompilationError;
import com.android.tools.r8.errors.Unimplemented;
import com.android.tools.r8.graph.Code;
import com.android.tools.r8.graph.DexAccessFlags;
import com.android.tools.r8.graph.DexAnnotationSet;
import com.android.tools.r8.graph.DexCode;
import com.android.tools.r8.graph.DexEncodedField;
import com.android.tools.r8.graph.DexEncodedMethod;
import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexProgramClass;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.graph.DexTypeList;
import java.util.ArrayList;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;

// Default and static method interface desugaring processor for interfaces.
//
// Makes default interface methods abstract, moves their implementation to
// a companion class. Removes bridge default methods.
//
// Also moves static interface methods into a companion class.
final class InterfaceProcessor {
  private final InterfaceMethodRewriter rewriter;
  // All created companion classes indexed by interface classes.
  final Map<DexProgramClass, DexProgramClass> companionClasses = new IdentityHashMap<>();

  InterfaceProcessor(InterfaceMethodRewriter rewriter) {
    this.rewriter = rewriter;
  }

  void process(DexProgramClass iface) {
    assert iface.isInterface();

    // The list of methods to be created in companion class.
    List<DexEncodedMethod> companionMethods = new ArrayList<>();

    // Process virtual interface methods first.
    List<DexEncodedMethod> remainingMethods = new ArrayList<>();
    for (DexEncodedMethod virtual : iface.virtualMethods()) {
      if (rewriter.isDefaultMethod(virtual)) {
        // Create a new method in a companion class to represent default method implementation.
        DexMethod companionMethod = rewriter.defaultAsMethodOfCompanionClass(virtual.method);

        Code code = virtual.getCode();
        if (code == null) {
          throw new CompilationError("Code is missing for default "
              + "interface method: " + virtual.method.toSourceString());
        }

        DexAccessFlags newFlags = new DexAccessFlags(virtual.accessFlags.get());
        newFlags.unsetBridge();
        newFlags.setStatic();
        DexCode dexCode = code.asDexCode();
        // TODO(ager): Should we give the new first parameter an actual name? Maybe 'this'?
        dexCode.setDebugInfo(dexCode.debugInfoWithAdditionalFirstParameter(null));
        assert (dexCode.getDebugInfo() == null)
            || (companionMethod.getArity() == dexCode.getDebugInfo().parameters.length);

        companionMethods.add(new DexEncodedMethod(companionMethod,
            newFlags, virtual.annotations, virtual.parameterAnnotations, code));

        // Make the method abstract.
        virtual.accessFlags.setAbstract();
        virtual.removeCode();
      }

      // Remove bridge methods.
      if (!virtual.accessFlags.isBridge()) {
        remainingMethods.add(virtual);
      }
    }

    // If at least one bridge methods was removed update the table.
    if (remainingMethods.size() < iface.virtualMethods().length) {
      iface.setVirtualMethods(remainingMethods.toArray(
          new DexEncodedMethod[remainingMethods.size()]));
    }
    remainingMethods.clear();

    // Process static methods, move them into companion class as well.
    for (DexEncodedMethod direct : iface.directMethods()) {
      if (direct.accessFlags.isPrivate()) {
        // We only expect to see private methods which are lambda$ methods,
        // and they are supposed to be relaxed to package private static methods
        // by this time by lambda rewriter.
        throw new Unimplemented("Private method are not yet supported.");
      }

      if (isStaticMethod(direct)) {
        companionMethods.add(new DexEncodedMethod(
            rewriter.staticAsMethodOfCompanionClass(direct.method), direct.accessFlags,
            direct.annotations, direct.parameterAnnotations, direct.getCode()));
      } else {
        // Since there are no interface constructors at this point,
        // this should only be class constructor.
        assert rewriter.factory.isClassConstructor(direct.method);
        remainingMethods.add(direct);
      }
    }
    if (remainingMethods.size() < iface.directMethods().length) {
      iface.setDirectMethods(remainingMethods.toArray(
          new DexEncodedMethod[remainingMethods.size()]));
    }

    if (companionMethods.isEmpty()) {
      return; // No methods to create, companion class not needed.
    }

    DexAccessFlags companionClassFlags = new DexAccessFlags(iface.accessFlags.get());
    companionClassFlags.unsetAbstract();
    companionClassFlags.unsetInterface();
    companionClassFlags.setFinal();
    companionClassFlags.setSynthetic();
    // Companion class must be public so moved methods can be called from anywhere.
    companionClassFlags.setPublic();

    // Create companion class.
    DexType companionClassType = rewriter.getCompanionClassType(iface.type);
    DexProgramClass companionClass = new DexProgramClass(
        companionClassType,
        null,
        companionClassFlags,
        rewriter.factory.objectType,
        DexTypeList.empty(),
        iface.sourceFile,
        DexAnnotationSet.empty(),
        DexEncodedField.EMPTY_ARRAY,
        DexEncodedField.EMPTY_ARRAY,
        companionMethods.toArray(new DexEncodedMethod[companionMethods.size()]),
        DexEncodedMethod.EMPTY_ARRAY
    );
    companionClasses.put(iface, companionClass);
  }

  private boolean isStaticMethod(DexEncodedMethod method) {
    if (method.accessFlags.isNative()) {
      throw new Unimplemented("Native interface methods are not yet supported.");
    }
    return method.accessFlags.isStatic() && !rewriter.factory.isClassConstructor(method.method);
  }
}