/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.jack.transformations.ast;

import com.android.jack.Options;
import com.android.jack.ir.ast.JExpression;
import com.android.jack.ir.ast.JExpressionStatement;
import com.android.jack.ir.ast.JMethod;
import com.android.jack.ir.ast.JVariableRef;
import com.android.jack.ir.ast.JVisitor;
import com.android.jack.transformations.request.Remove;
import com.android.jack.transformations.request.TransformationRequest;
import com.android.jack.transformations.threeaddresscode.ThreeAddressCodeForm;
import com.android.jack.util.filter.Filter;
import com.android.sched.item.Description;
import com.android.sched.item.Name;
import com.android.sched.schedulable.Constraint;
import com.android.sched.schedulable.RunnableSchedulable;
import com.android.sched.schedulable.Transform;
import com.android.sched.util.config.ThreadConfig;

import javax.annotation.Nonnull;

/**
 * Remove {@code JExpressionStatement} containing directly a {@code JVariableRef} or a
 * {@code JArrayRef} ie code like {@code lv;}.
 */
@Description("Remove JVariableRef and JArrayRef as JExpressionStatement.")
@Name("RefAsStatementRemover")
@Constraint(need = {ThreeAddressCodeForm.class})
@Transform(remove = RefAsStatement.class)
public class RefAsStatementRemover implements RunnableSchedulable<JMethod> {

  @Nonnull
  private final Filter<JMethod> filter = ThreadConfig.get(Options.METHOD_FILTER);

  private static class Visitor extends JVisitor {

    @Nonnull
    private final TransformationRequest tr;

    public Visitor(@Nonnull TransformationRequest tr) {
      this.tr = tr;
    }

    @Override
    public boolean visit(@Nonnull JExpressionStatement expressionStatement) {
      JExpression expr = expressionStatement.getExpr();

      if (expr instanceof JVariableRef) {
        tr.append(new Remove(expressionStatement));
        return false;
      } else {
        return super.visit(expressionStatement);
      }
    }
  }

  @Override
  public void run(@Nonnull JMethod method) throws Exception {
    if (method.getEnclosingType().isExternal() || method.isNative() || method.isAbstract()
        || !filter.accept(this.getClass(), method)) {
      return;
    }

    TransformationRequest tr = new TransformationRequest(method);
    Visitor visitor = new Visitor(tr);
    visitor.accept(method);
    tr.commit();
  }

}