//
// Copyright (C) 2006 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.Conditional;
import cmu.conditional.One;
import de.fosd.typechef.featureexpr.FeatureExpr;
import gov.nasa.jpf.JPFException;
import gov.nasa.jpf.vm.ChoiceGenerator;
import gov.nasa.jpf.vm.ElementInfo;
import gov.nasa.jpf.vm.Instruction;
import gov.nasa.jpf.vm.MJIEnv;
import gov.nasa.jpf.vm.StackFrame;
import gov.nasa.jpf.vm.ThreadInfo;
import gov.nasa.jpf.vm.VM;

/**
 * Enter monitor for object
 * ..., objectref => ...
 */
public class MONITORENTER extends LockInstruction {

	public Conditional<Instruction> execute(FeatureExpr ctx, final ThreadInfo ti) {
		StackFrame frame = ti.getTopFrame();

		final MONITORENTER thisInstruction = this;

		Conditional<Integer> objref = frame.peek(ctx); // Don't pop yet before we know we really enter
		return objref.mapf(ctx, new BiFunction<FeatureExpr, Integer, Conditional<Instruction>>() {

			@Override
			public Conditional<Instruction> apply(FeatureExpr ctx, Integer objref) {
				if (objref == MJIEnv.NULL) {
					return new One<>(ti.createAndThrowException(ctx, "java.lang.NullPointerException", "Attempt to acquire lock for null object"));
				}

				lastLockRef = objref;
				ElementInfo ei = ti.getModifiableElementInfo(objref);

				if (!ti.isFirstStepInsn()) { // check if we have a choicepoint
					if (!isLockOwner(ti, ei)) { // maybe its a recursive lock
						VM vm = ti.getVM();

						if (ei.canLock(ti)) { // we can lock the object, the CG is optional
							ei = ei.getInstanceWithUpdatedSharedness(ti);
							if (ei.isShared()) {
								ChoiceGenerator<?> cg = vm.getSchedulerFactory().createMonitorEnterCG(ei, ti);
								if (cg != null) {
									if (vm.setNextChoiceGenerator(cg)) {
										ei.registerLockContender(ti); // Record that this thread would lock the object upon next execution
										return new One<Instruction>(thisInstruction);
									}
								}
							}

						} else { // already locked by another thread, we have to block and therefore need a CG
							// the top half already did set the object shared

							ei.block(ti); // do this before we obtain the CG so that this thread is not in its choice set

							ChoiceGenerator<?> cg = vm.getSchedulerFactory().createMonitorEnterCG(ei, ti);
							if (cg != null) {
								if (vm.setNextChoiceGenerator(cg)) {
									return new One<Instruction>(thisInstruction);
								} else {
									throw new JPFException("listener did override ChoiceGenerator for blocking MONITOR_ENTER");
								}
							} else {
								throw new JPFException("scheduling policy did not return ChoiceGenerator for blocking MONITOR_ENTER");
							}
						}
					}
				}

				// this is only executed in the bottom half
				StackFrame frame = ti.getModifiableTopFrame(); // now we need to modify it
				frame.pop(ctx);
				ei.lock(ti); // Still have to increment the lockCount

				return getNext(ctx, ti);
			}

		});

	}

	public int getByteCode() {
		return 0xC2;
	}

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