// Copyright (c) 2018, 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.optimize.string;

import static com.android.tools.r8.ir.optimize.CodeRewriter.removeOrReplaceByDebugLocalWrite;
import static com.android.tools.r8.ir.optimize.ReflectionOptimizer.ClassNameComputationInfo.ClassNameComputationOption.CANONICAL_NAME;
import static com.android.tools.r8.ir.optimize.ReflectionOptimizer.ClassNameComputationInfo.ClassNameComputationOption.NAME;
import static com.android.tools.r8.ir.optimize.ReflectionOptimizer.ClassNameComputationInfo.ClassNameComputationOption.SIMPLE_NAME;
import static com.android.tools.r8.ir.optimize.ReflectionOptimizer.computeClassName;

import com.android.tools.r8.graph.AppInfo;
import com.android.tools.r8.graph.DexClass;
import com.android.tools.r8.graph.DexItemFactory;
import com.android.tools.r8.graph.DexMethod;
import com.android.tools.r8.graph.DexType;
import com.android.tools.r8.ir.analysis.type.TypeLatticeElement;
import com.android.tools.r8.ir.code.BasicBlock.ThrowingInfo;
import com.android.tools.r8.ir.code.ConstClass;
import com.android.tools.r8.ir.code.ConstNumber;
import com.android.tools.r8.ir.code.ConstString;
import com.android.tools.r8.ir.code.DexItemBasedConstString;
import com.android.tools.r8.ir.code.IRCode;
import com.android.tools.r8.ir.code.Instruction;
import com.android.tools.r8.ir.code.InstructionIterator;
import com.android.tools.r8.ir.code.InvokeStatic;
import com.android.tools.r8.ir.code.InvokeVirtual;
import com.android.tools.r8.ir.code.Value;
import com.android.tools.r8.ir.optimize.ReflectionOptimizer.ClassNameComputationInfo;
import com.android.tools.r8.utils.InternalOptions;
import java.util.function.BiFunction;
import java.util.function.Function;

public class StringOptimizer {

  private final ThrowingInfo throwingInfo;

  public StringOptimizer(InternalOptions options) {
    throwingInfo = options.isGeneratingClassFiles()
        ? ThrowingInfo.NO_THROW : ThrowingInfo.CAN_THROW;
  }

  // int String#length()
  // boolean String#isEmpty()
  // boolean String#startsWith(str)
  // boolean String#endsWith(str)
  // boolean String#contains(str)
  // boolean String#equals(str)
  // boolean String#equalsIgnoreCase(str)
  // boolean String#contentEquals(str)
  public void computeTrivialOperationsOnConstString(IRCode code, DexItemFactory factory) {
    if (!code.hasConstString) {
      return;
    }
    InstructionIterator it = code.instructionIterator();
    while (it.hasNext()) {
      Instruction instr = it.next();
      if (!instr.isInvokeVirtual()) {
        continue;
      }
      InvokeVirtual invoke = instr.asInvokeVirtual();
      DexMethod invokedMethod = invoke.getInvokedMethod();
      Function<String, Integer> operatorWithNoArg = null;
      BiFunction<String, String, Integer> operatorWithString = null;
      if (invokedMethod == factory.stringMethods.length) {
        operatorWithNoArg = String::length;
      } else if (invokedMethod == factory.stringMethods.isEmpty) {
        operatorWithNoArg = rcv -> rcv.isEmpty() ? 1 : 0;
      } else if (invokedMethod == factory.stringMethods.contains) {
        operatorWithString = (rcv, arg) -> rcv.contains(arg) ? 1 : 0;
      } else if (invokedMethod == factory.stringMethods.startsWith) {
        operatorWithString = (rcv, arg) -> rcv.startsWith(arg) ? 1 : 0;
      } else if (invokedMethod == factory.stringMethods.endsWith) {
        operatorWithString = (rcv, arg) -> rcv.endsWith(arg) ? 1 : 0;
      } else if (invokedMethod == factory.stringMethods.equals) {
        operatorWithString = (rcv, arg) -> rcv.equals(arg) ? 1 : 0;
      } else if (invokedMethod == factory.stringMethods.equalsIgnoreCase) {
        operatorWithString = (rcv, arg) -> rcv.equalsIgnoreCase(arg) ? 1 : 0;
      } else if (invokedMethod == factory.stringMethods.contentEqualsCharSequence) {
        operatorWithString = (rcv, arg) -> rcv.contentEquals(arg) ? 1 : 0;
      }
      if (operatorWithNoArg == null && operatorWithString == null) {
        continue;
      }
      Value rcv = invoke.getReceiver().getAliasedValue();
      if (rcv.definition == null
          || !rcv.definition.isConstString()
          || !rcv.isConstant()) {
        continue;
      }
      if (operatorWithNoArg != null) {
        assert invoke.inValues().size() == 1;
        ConstString rcvString = rcv.definition.asConstString();
        int v = operatorWithNoArg.apply(rcvString.getValue().toString());
        ConstNumber constNumber = code.createIntConstant(v);
        it.replaceCurrentInstruction(constNumber);
      } else {
        assert operatorWithString != null;
        assert invoke.inValues().size() == 2;
        Value arg = invoke.inValues().get(1).getAliasedValue();
        if (arg.definition == null
            || !arg.definition.isConstString()
            || !arg.isConstant()) {
          continue;
        }
        ConstString rcvString = rcv.definition.asConstString();
        ConstString argString = arg.definition.asConstString();
        int v = operatorWithString.apply(
            rcvString.getValue().toString(), argString.getValue().toString());
        ConstNumber constNumber = code.createIntConstant(v);
        it.replaceCurrentInstruction(constNumber);
      }
    }
  }

  // Find Class#get*Name() with a constant-class and replace it with a const-string if possible.
  public void rewriteClassGetName(IRCode code, AppInfo appInfo) {
    boolean markUseIdentifierNameString = false;
    InstructionIterator it = code.instructionIterator();
    while (it.hasNext()) {
      Instruction instr = it.next();
      if (!instr.isInvokeVirtual()) {
        continue;
      }
      InvokeVirtual invoke = instr.asInvokeVirtual();
      DexMethod invokedMethod = invoke.getInvokedMethod();
      if (!appInfo.dexItemFactory.classMethods.isReflectiveNameLookup(invokedMethod)) {
        continue;
      }
      assert invoke.inValues().size() == 1;
      // In case of handling multiple invocations over the same const-string, all the following
      // usages after the initial one will point to non-null IR (a.k.a. alias), e.g.,
      //
      //   rcv <- invoke-virtual instance, ...#getClass() // Can be rewritten to const-class
      //   x <- invoke-virtual rcv, Class#getName()
      //   non_null_rcv <- non-null rcv
      //   y <- invoke-virtual non_null_rcv, Class#getCanonicalName()
      //   z <- invoke-virtual non_null_rcv, Class#getSimpleName()
      //   ... // or some other usages of the same usage.
      //
      // In that case, we should check if the original source is (possibly rewritten) const-class.
      Value in = invoke.getReceiver().getAliasedValue();
      if (in.definition == null
          || !in.definition.isConstClass()
          || !in.isConstant()) {
        continue;
      }

      ConstClass constClass = in.definition.asConstClass();
      DexType type = constClass.getValue();
      int arrayDepth = type.getNumberOfLeadingSquareBrackets();
      DexType baseType = type.toBaseType(appInfo.dexItemFactory);
      // Make sure base type is a class type.
      if (!baseType.isClassType()) {
        continue;
      }
      DexClass holder = appInfo.definitionFor(baseType);
      if (holder == null) {
        continue;
      }

      DexItemBasedConstString deferred = null;
      String name = null;
      if (invokedMethod == appInfo.dexItemFactory.classMethods.getName) {
        if (code.options.enableMinification) {
          deferred = new DexItemBasedConstString(
              invoke.outValue(), baseType, new ClassNameComputationInfo(NAME, arrayDepth));
        } else {
          name = computeClassName(baseType.toDescriptorString(), holder, NAME, arrayDepth);
        }
      } else if (invokedMethod == appInfo.dexItemFactory.classMethods.getTypeName) {
        // TODO(b/119426668): desugar Type#getTypeName
        continue;
      } else if (invokedMethod == appInfo.dexItemFactory.classMethods.getCanonicalName) {
        // Always returns null if the target type is local or anonymous class.
        if (holder.isLocalClass() || holder.isAnonymousClass()) {
          ConstNumber constNull = code.createConstNull();
          it.replaceCurrentInstruction(constNull);
        } else {
          if (code.options.enableMinification) {
            deferred =
                new DexItemBasedConstString(
                    invoke.outValue(),
                    baseType,
                    new ClassNameComputationInfo(CANONICAL_NAME, arrayDepth));
          } else {
            name = computeClassName(
                baseType.toDescriptorString(), holder, CANONICAL_NAME, arrayDepth);
          }
        }
      } else if (invokedMethod == appInfo.dexItemFactory.classMethods.getSimpleName) {
        // Always returns an empty string if the target type is an anonymous class.
        if (holder.isAnonymousClass()) {
          name = "";
        } else {
          if (code.options.enableMinification) {
            deferred = new DexItemBasedConstString(
                invoke.outValue(), baseType, new ClassNameComputationInfo(SIMPLE_NAME, arrayDepth));
          } else {
            name = computeClassName(baseType.toDescriptorString(), holder, SIMPLE_NAME, arrayDepth);
          }
        }
      }
      if (name != null) {
        Value stringValue =
            code.createValue(TypeLatticeElement.stringClassType(appInfo), invoke.getLocalInfo());
        ConstString constString =
            new ConstString(stringValue, appInfo.dexItemFactory.createString(name), throwingInfo);
        it.replaceCurrentInstruction(constString);
      } else if (deferred != null) {
        it.replaceCurrentInstruction(deferred);
        markUseIdentifierNameString = true;
      }
    }
    if (markUseIdentifierNameString) {
      code.method.getMutableOptimizationInfo().markUseIdentifierNameString();
    }
  }

  // String#valueOf(null) -> "null"
  // String#valueOf(String s) -> s
  // str.toString() -> str
  public void removeTrivialConversions(IRCode code, AppInfo appInfo) {
    InstructionIterator it = code.instructionIterator();
    while (it.hasNext()) {
      Instruction instr = it.next();
      if (instr.isInvokeStatic()) {
        InvokeStatic invoke = instr.asInvokeStatic();
        DexMethod invokedMethod = invoke.getInvokedMethod();
        if (invokedMethod != appInfo.dexItemFactory.stringMethods.valueOf) {
          continue;
        }
        assert invoke.inValues().size() == 1;
        Value in = invoke.inValues().get(0);
        if (in.hasLocalInfo()) {
          continue;
        }
        TypeLatticeElement inType = in.getTypeLattice();
        if (inType.isConstantNull()) {
          Value nullStringValue =
              code.createValue(TypeLatticeElement.stringClassType(appInfo), invoke.getLocalInfo());
          ConstString nullString = new ConstString(
              nullStringValue, appInfo.dexItemFactory.createString("null"), throwingInfo);
          it.replaceCurrentInstruction(nullString);
        } else if (inType.nullElement().isDefinitelyNotNull()
            && inType.isClassType()
            && inType.asClassTypeLatticeElement().getClassType()
                .equals(appInfo.dexItemFactory.stringType)) {
          Value out = invoke.outValue();
          if (out != null) {
            removeOrReplaceByDebugLocalWrite(invoke, it, in, out);
          } else {
            it.removeOrReplaceByDebugLocalRead();
          }
        }
      } else if (instr.isInvokeVirtual()) {
        InvokeVirtual invoke = instr.asInvokeVirtual();
        DexMethod invokedMethod = invoke.getInvokedMethod();
        if (invokedMethod != appInfo.dexItemFactory.stringMethods.toString) {
          continue;
        }
        assert invoke.inValues().size() == 1;
        Value in = invoke.getReceiver();
        TypeLatticeElement inType = in.getTypeLattice();
        if (inType.nullElement().isDefinitelyNotNull()
            && inType.isClassType()
            && inType.asClassTypeLatticeElement().getClassType()
                .equals(appInfo.dexItemFactory.stringType)) {
          Value out = invoke.outValue();
          if (out != null) {
            removeOrReplaceByDebugLocalWrite(invoke, it, in, out);
          } else {
            it.removeOrReplaceByDebugLocalRead();
          }
        }
      }
    }
  }

}