/*
 * TeleStax, Open Source Cloud Communications
 * Copyright 2011-2014, Telestax Inc and individual contributors
 * by the @authors tag.
 *
 * This program is free software: you can redistribute it and/or modify
 * under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */
package org.restcomm.connect.commons.fsm;

import static com.google.common.base.Preconditions.*;

import org.restcomm.connect.commons.annotations.concurrency.Immutable;

/**
 * @author quintana.thomas@gmail.com (Thomas Quintana)
 */
@Immutable
public final class Transition {
    private final Guard guard;
    private final State stateOnEnter;
    private final State stateOnExit;

    public Transition(final State stateOnEnter, final State stateOnExit, final Guard guard) {
        super();
        checkNotNull(stateOnEnter, "A transition can not have a null value for the state on enter.");
        checkNotNull(stateOnExit, "A transition can not have a null value for the state on exit.");
        this.guard = guard;
        this.stateOnEnter = stateOnEnter;
        this.stateOnExit = stateOnExit;
    }

    public Transition(final State stateOnEnter, final State stateOnExit) {
        this(stateOnEnter, stateOnExit, null);
    }

    @Override
    public boolean equals(final Object object) {
        if (this == object) {
            return true;
        } else if (object == null) {
            return false;
        } else if (getClass() != object.getClass()) {
            return false;
        }
        final Transition transition = (Transition) object;
        if (!stateOnEnter.equals(transition.getStateOnEnter())) {
            return false;
        }
        if (!stateOnExit.equals(transition.getStateOnExit())) {
            return false;
        }
        return true;
    }

    public Guard getGuard() {
        return guard;
    }

    public State getStateOnEnter() {
        return stateOnEnter;
    }

    public State getStateOnExit() {
        return stateOnExit;
    }

    @Override
    public int hashCode() {
        final int prime = 5;
        int result = 1;
        result = prime * result + stateOnEnter.hashCode();
        result = prime * result + stateOnExit.hashCode();
        return result;
    }
}
