package.ts

// Learn TypeScript:
//  - https://docs.cocos.com/creator/2.4/manual/en/scripting/typescript.html
// Learn Attribute:
//  - https://docs.cocos.com/creator/2.4/manual/en/scripting/reference/attributes.html
// Learn life-cycle callbacks:
//  - https://docs.cocos.com/creator/2.4/manual/en/scripting/life-cycle-callbacks.html

import Protocol from "./protocol";

const { ccclass, property } = cc._decorator;

@ccclass
export default class Package {
    static TYPE_HANDSHAKE = 1;
    static TYPE_HANDSHAKE_ACK = 2;
    static TYPE_HEARTBEAT = 3;
    static TYPE_DATA = 4;
    static TYPE_KICK = 5;
    /**
     * Package protocol encode.
     *
     * Pomelo package format:
     * +------+-------------+------------------+
     * | type | body length |       body       |
     * +------+-------------+------------------+
     *
     * Head: 4bytes
     *   0: package type,
     *      1 - handshake,
     *      2 - handshake ack,
     *      3 - heartbeat,
     *      4 - data
     *      5 - kick
     *   1 - 3: big-endian body length
     * Body: body length bytes
     *
     * @param  {Number}    type   package type
     * @param  {ByteArray} body   body content in bytes
     * @return {ByteArray}        new byte array that contains encode result
     */
    static encode(type, body?) {
        var length = body ? body.length : 0;
        var buffer = new Uint8Array(Protocol.PKG_HEAD_BYTES + length);
        var index = 0;
        buffer[index++] = type & 0xff;
        buffer[index++] = (length >> 16) & 0xff;
        buffer[index++] = (length >> 8) & 0xff;
        buffer[index++] = length & 0xff;
        if (body) {
            Protocol.copyArray(buffer, index, body, 0, length);
        }
        return buffer;
    };

    /**
     * Package protocol decode.
     * See encode for package format.
     *
     * @param  {ByteArray} buffer byte array containing package content
     * @return {Object}           {type: package type, buffer: body byte array}
     */
    static decode(buffer) {
        var offset = 0;
        var bytes = new Uint8Array(buffer);
        var length = 0;
        var rs = [];
        while (offset < bytes.length) {
            var type = bytes[offset++];
            length = ((bytes[offset++]) << 16 | (bytes[offset++]) << 8 | bytes[offset++]) >>> 0;
            var body = length ? new Uint8Array(length) : null;
            Protocol.copyArray(body, 0, bytes, offset, length);
            offset += length;
            rs.push({ 'type': type, 'body': body });
        }
        return rs.length === 1 ? rs[0] : rs;
    };
}