/**
 * Copyright (C) 2010-2017 Gordon Fraser, Andrea Arcuri and EvoSuite
 * contributors
 *
 * This file is part of EvoSuite.
 *
 * EvoSuite is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3.0 of the License, or
 * (at your option) any later version.
 *
 * EvoSuite is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with EvoSuite. If not, see <http://www.gnu.org/licenses/>.
 */
/**
 * 
 */
package org.evosuite.contracts;

import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;

import org.evosuite.assertion.EqualsAssertion;
import org.evosuite.testcase.execution.Scope;
import org.evosuite.testcase.statements.MethodStatement;
import org.evosuite.testcase.statements.PrimitiveExpression;
import org.evosuite.testcase.statements.PrimitiveExpression.Operator;
import org.evosuite.testcase.statements.Statement;
import org.evosuite.testcase.TestCase;
import org.evosuite.testcase.variable.VariableReference;
import org.evosuite.testcase.variable.VariableReferenceImpl;
import org.evosuite.utils.generic.GenericMethod;

/**
 * o1.equals(o2) => o1.hashCode() == o2.hashCode()
 * 
 * @author Gordon Fraser
 */
public class EqualsHashcodeContract extends Contract {

	/* (non-Javadoc)
	 * @see org.evosuite.contracts.Contract#check(org.evosuite.testcase.Statement, org.evosuite.testcase.Scope, java.lang.Throwable)
	 */
	/** {@inheritDoc} */
	@Override
	public ContractViolation check(Statement statement, Scope scope,
	        Throwable exception) {
		for (Pair<VariableReference> pair : getAllVariablePairs(scope)) {
			if(pair.object1 == pair.object2)
				continue;

			Object object1 = scope.getObject(pair.object1);
			Object object2 = scope.getObject(pair.object2);
			if (object1 == null || object2 == null)
				continue;

			// We do not want to call hashcode if it is the default implementation
			Class<?>[] parameters = { Object.class };
			try {
				Method equalsMethod = object1.getClass().getMethod("equals", parameters);
				Method hashCodeMethod = object1.getClass().getMethod("hashCode",
				                                                     new Class<?>[0]);
				if (equalsMethod.getDeclaringClass().equals(Object.class)
				        || hashCodeMethod.getDeclaringClass().equals(Object.class))
					continue;

			} catch (SecurityException e1) {
				continue;
			} catch (NoSuchMethodException e1) {
				continue;
			}

			if (object1.equals(object2)) {
				if (object1.hashCode() != object2.hashCode()) {
					return new ContractViolation(this, statement, exception,
					        pair.object1, pair.object2);
				}
			} else {
				if (object1.hashCode() == object2.hashCode()) {
					return new ContractViolation(this, statement, exception,
					        pair.object1, pair.object2);
				}
			}
		}
		return null;
	}

	@Override
	public void addAssertionAndComments(Statement statement,
	        List<VariableReference> variables, Throwable exception) {
		TestCase test = statement.getTestCase();

		VariableReference a = variables.get(0);
		VariableReference b = variables.get(1);
		try {
			Method equalsMethod = a.getGenericClass().getRawClass().getMethod("equals",
			                                                                  new Class<?>[] { Object.class });
			Method hashCodeMethod = a.getGenericClass().getRawClass().getMethod("hashCode",
			                                                                    new Class<?>[] {});

			GenericMethod genericEqualsMethod = new GenericMethod(equalsMethod,
			        a.getGenericClass());
			GenericMethod genericHashCodeMethod = new GenericMethod(hashCodeMethod,
			        a.getGenericClass());

			// Create x = a.equals(b)
			Statement st1 = new MethodStatement(test, genericEqualsMethod, a,
			        Arrays.asList(new VariableReference[] { b }));
			VariableReference x = test.addStatement(st1, statement.getPosition() + 1);

			// Create y = a.hashCode();
			Statement st2 = new MethodStatement(test, genericHashCodeMethod, a,
			        Arrays.asList(new VariableReference[] {}));
			VariableReference y = test.addStatement(st2, statement.getPosition() + 2);

			// Create z = b.hashCode();
			Statement st3 = new MethodStatement(test, genericHashCodeMethod, b,
			        Arrays.asList(new VariableReference[] {}));
			VariableReference z = test.addStatement(st3, statement.getPosition() + 3);

			// Create w = z == z
			VariableReference w = new VariableReferenceImpl(test, boolean.class);
			PrimitiveExpression exp = new PrimitiveExpression(test, w, y,
			        Operator.EQUALS, z);
			w = test.addStatement(exp, statement.getPosition() + 4);

			Statement newStatement = test.getStatement(w.getStPosition());

			// Create assertEquals(x, w)
			EqualsAssertion assertion = new EqualsAssertion();
			assertion.setStatement(newStatement);
			assertion.setSource(x);
			assertion.setDest(w);
			assertion.setValue(true);
			newStatement.addAssertion(assertion);
			newStatement.addComment("Violates contract equals - hashcode");

		} catch (NoSuchMethodException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	/** {@inheritDoc} */
	@Override
	public String toString() {
		return "Equals hashcode check";
	}

}