content: /*
   * 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 io.airlift.bytecode.control;
  
  import com.google.common.collect.ImmutableList;
  import io.airlift.bytecode.BytecodeBlock;
  import io.airlift.bytecode.BytecodeNode;
  import io.airlift.bytecode.BytecodeVisitor;
  import io.airlift.bytecode.MethodGenerationContext;
  import io.airlift.bytecode.instruction.LabelNode;
  import org.objectweb.asm.MethodVisitor;
  
  import java.util.List;
  
  import static com.google.common.base.Preconditions.checkState;
  
  public class IfStatement
          implements FlowControl
  {
      private final String comment;
      private final BytecodeBlock condition = new BytecodeBlock();
      private final BytecodeBlock ifTrue = new BytecodeBlock();
      private final BytecodeBlock ifFalse = new BytecodeBlock();
  
      private final LabelNode falseLabel = new LabelNode("false");
      private final LabelNode outLabel = new LabelNode("out");
  
      public IfStatement()
      {
          this.comment = null;
      }
  
      public IfStatement(String format, Object... args)
      {
          this.comment = String.format(format, args);
      }
  
      @Override
      public String getComment()
      {
          return comment;
      }
  
      public BytecodeBlock condition()
      {
          return condition;
      }
  
      public IfStatement condition(BytecodeNode node)
      {
          checkState(condition.isEmpty(), "condition already set");
          condition.append(node);
          return this;
      }
  
      public BytecodeBlock ifTrue()
      {
          return ifTrue;
      }
  
      public IfStatement ifTrue(BytecodeNode node)
      {
          checkState(ifTrue.isEmpty(), "ifTrue already set");
          ifTrue.append(node);
          return this;
      }
  
      public BytecodeBlock ifFalse()
      {
          return ifFalse;
      }
  
      public IfStatement ifFalse(BytecodeNode node)
      {
          checkState(ifFalse.isEmpty(), "ifFalse already set");
          ifFalse.append(node);
          return this;
      }
  
      @Override
      public void accept(MethodVisitor visitor, MethodGenerationContext generationContext)
      {
          checkState(!condition.isEmpty(), "IfStatement does not have a condition set");
          checkState(!ifTrue.isEmpty() || !ifFalse.isEmpty(), "IfStatement does not have a true or false block set");
  
          BytecodeBlock block = new BytecodeBlock();
  
          // if !condition goto false;
          block.append(new BytecodeBlock()
                  .setDescription("condition")
                  .append(condition));
          block.ifFalseGoto(falseLabel);
  
          if (!ifTrue.isEmpty()) {
              block.append(new BytecodeBlock()
                      .setDescription("ifTrue")
                      .append(ifTrue));
          }
  
          if (!ifFalse.isEmpty()) {
              // close true case by skipping to end
              block.gotoLabel(outLabel);
  
              block.visitLabel(falseLabel);
              block.append(new BytecodeBlock()
                      .setDescription("ifFalse")
                      .append(ifFalse));
              block.visitLabel(outLabel);
          }
          else {
              block.visitLabel(falseLabel);
          }
  
          block.accept(visitor, generationContext);
      }
  
      @Override
      public List<BytecodeNode> getChildNodes()
      {
          return ImmutableList.of(condition, ifTrue, ifFalse);
      }
  
      @Override
      public <T> T accept(BytecodeNode parent, BytecodeVisitor<T> visitor)
      {
          return visitor.visitIf(parent, this);
      }
  }
  