//
// Copyright (C) 2010 United States Government as represented by the
// Administrator of the National Aeronautics and Space Administration
// (NASA).  All Rights Reserved.
//
// This software is distributed under the NASA Open Source Agreement
// (NOSA), version 1.3.  The NOSA has been approved by the Open Source
// Initiative.  See the file NOSA-1.3-JPF at the top of the distribution
// directory tree for the complete NOSA document.
//
// THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
// KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
// LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
// SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
// A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT
// THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
// DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
//

package gov.nasa.jpf.jvm.bytecode;

import java.util.function.BiFunction;
import cmu.conditional.ChoiceFactory;
import cmu.conditional.Conditional;
import cmu.conditional.One;
import de.fosd.typechef.featureexpr.FeatureExpr;
import gov.nasa.jpf.jvm.JVMInstruction;
import gov.nasa.jpf.vm.Instruction;
import gov.nasa.jpf.vm.StackFrame;
import gov.nasa.jpf.vm.ThreadInfo;

/**
 * this is used to return from a DirectCallStackFrame
 *
 * Note that it is NOT a ReturnInstruction, in case listeners monitor these
 * and expect corresponding InvokeInstructions. Although this would seem intuitive, it
 * would be pointless to derive because the ReturnInstruction.enter() does
 * a lot of things we would have to cut off, i.e. it would require more effort
 * to undo this (no sync, no return value, no pc advance on the returned-to
 * stackframe etc.)
 *
 * However, having a dedicated direct call return instruction makes sense so
 * that the ReturnInstruction of the called method does not have to handle
 * direct calls specifically
 */
public class DIRECTCALLRETURN extends JVMInstruction implements gov.nasa.jpf.vm.ReturnInstruction {

  @Override
  public boolean isExtendedInstruction() {
    return true;
  }

  public static final int OPCODE = 261;

  @Override
  public int getByteCode () {
    return OPCODE;
  }

  @Override
  public void accept(InstructionVisitor insVisitor) {
	  insVisitor.visit(this);
  }

  @SuppressWarnings("unchecked")
@Override
  public Conditional<Instruction> execute (FeatureExpr ctx, ThreadInfo ti) {
    // pop the current frame but do not advance the new top frame, and do
    // not touch its operand stack
    
    if (ti.getStackDepth() == 1){ // thread exit point (might be re-executed)
    
      if (!ti.exit(ctx)){
        return new One<Instruction>(this); // repeat, we couldn't get the lock
      } else {
        return (Conditional<Instruction>) One.NULL;
      }      
      
    } else {
      StackFrame frame = ti.popDirectCallFrame(ctx);
      return frame.getPC();
    }
  }
  
	@Override
	public Conditional<Instruction> getNext(final FeatureExpr ctx, ThreadInfo ti) {
		return ti.getPC().mapf(ctx, new BiFunction<FeatureExpr, Instruction, Conditional<Instruction>>() {

			@Override
			public Conditional<Instruction> apply(final FeatureExpr f, final Instruction y) {
				return ChoiceFactory.create(ctx, new One<>(y.getNext()), new One<>(y));
			}

		}).simplify();
	}
}