/*
 * Copyright (c) 2015 Cable Television Laboratories, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */

package org.pcmm.gates.impl;

import org.pcmm.gates.ISessionClassID;

/**
 * SessionClassID is a 1-byte unsigned integer value which identifies the proper admission control policy or
 * parameters to be applied for this Gate. The SessionClassID is a bit field, defined as follows:
 *   Bit 0-2: Priority, a number from 0 to 7, where 0 is low priority and 7 is high.
 *   Bit 3: Preemption, set to enable preemption of bandwidth allocated to lower priority sessions if necessary
 *   (if supported).
 *   Bit 4-7: Configurable, default to 0
 */
public class SessionClassID implements ISessionClassID {

    /**
     * The priority field describes the relative importance of the session as compared to other sessions generated by
     * the same PDP. The PEP MAY use this value to both implement priority based admission (in conjunction with the
     * Preemption bit), and to defend the resulting flow from being preempted.
     */
    private transient byte priority;

    /**
     * The preemption bit is used to by a PDP to direct the PEP to apply a priority-based admission control. Preemption
     * support is optional; a PEP MAY ignore this bit. If preemption is not requested by the PDP or not implement by the
     * PEP, then admission control policy will be on a first-come, first-served basis.
     */
    private transient byte preemption;

    /**
     * The session ID value
     */
    private byte session;

    /**
     * Constructor 1
     * @param value - the session value
     */
    public SessionClassID(byte value) {
        this.session = value;
        this.priority = 0;
        this.preemption = 0;
        priority |= value >> 2;
        preemption |= value >> 3;
    }

    /**
     * Constructor 2
     * @param value - the session value
     * @param priority - overrides the default priority value of 2
     * @param preemption - overrides the default preemption value of 3
     */
    public SessionClassID(byte value, final byte priority, final byte preemption) {
        this.session = value;
        this.priority = priority;
        this.preemption = preemption;
    }

    @Override
    public byte getPriority() {
        return priority;
    }

    @Override
    public byte getPreemption() {
        return preemption;
    }

    @Override
    public byte toSingleByte() {
        return session;
    }

    @Override
    public boolean equals(final Object o) {
        if (this == o) {
            return true;
        }
        if (!(o instanceof SessionClassID)) {
            return false;
        }
        final SessionClassID that = (SessionClassID) o;
        return priority == that.priority && preemption == that.preemption && session == that.session;
    }

    @Override
    public int hashCode() {
        int result = (int) priority;
        result = 31 * result + (int) preemption;
        result = 31 * result + (int) session;
        return result;
    }
}