'use strict';

/**
 * 2个字节是16位（二进制），共能表示2^16=65536个数。但由于数是有符号的，最高位用作符号位，所以只有低15位表示绝对值。
 * 整型在内存中以补码存储，能表示的最大正整数是2^15-1=32767。
 */

const net = require('node:net');
const { Stick, MaxBodyLen } = require('@lvgithub/stick');

const stick = new Stick(1024).setReadIntBE('32');
stick.setMaxBodyLen(MaxBodyLen['2048M']);

const LOCAL_PORT = 1936;

/**
 * 头长度(Byte)
 */
const HEAD_LEN = 4;

/**
 * 标识长度(Byte)
 */
const IDENTIFIER_LEN = 2;

/**
 * 媒体服务器映射
 */
const MEDIA_SERVER_MAP = new Map([
    ['9999', { port: 1935, host: '192.168.66.73' }],
]);

/**
 * 媒体服务器连接池
 */
const MEDIA_SERVER_POOLS = new Map();

/**
 * 初始化多媒体服务器连接池
 */
for (let [key, value] of MEDIA_SERVER_MAP) {
    const socket = net.createConnection({ host: value.host, port: value.port });
    MEDIA_SERVER_POOLS.set(key, socket);
}

/**
 * 关闭所有目标服务器连接
 */
const closeAllTargetSocket = function () {
    for (let [, value] of MEDIA_SERVER_POOLS) {
        value.end();
    }
};

const proxy = net.createServer(function (socket) {
    socket.on('data', function (data) {
        stick.putData(data);
    });

    stick.onData(function (data) {
        const totalHeadLen = HEAD_LEN + IDENTIFIER_LEN;

        // 解析包头长度
        const head = Buffer.alloc(HEAD_LEN);
        data.copy(head, 0, 0, HEAD_LEN);
        const dataLen = head.readInt32BE() - IDENTIFIER_LEN;

        // 解析标识
        const identifier = Buffer.alloc(IDENTIFIER_LEN);
        data.copy(identifier, 0, HEAD_LEN, totalHeadLen);

        // 解析数据包内容
        const body = Buffer.alloc(dataLen);
        data.copy(body, 0, totalHeadLen, head.readInt32BE() + HEAD_LEN);

        const mediaId = identifier.readInt16BE() + '';
        console.log('data length: ' + dataLen);
        console.log('identifier content: ' + mediaId);
        // console.log('body content: ' + body.toString('hex'));

        if (MEDIA_SERVER_POOLS.has(mediaId)) {
            const mediaServer = MEDIA_SERVER_MAP.get(mediaId);
            console.log('matched media server: %s:%s', mediaServer.host, mediaServer.port);
            const targetSocket = MEDIA_SERVER_POOLS.get(mediaId);
            /** 测试代码START: 正式环境为一个代理网关对应多个媒体服务  */
            if (targetSocket.listeners('data').length === 0) {
                targetSocket.on('data', function (chunk) {
                    // TODO 向客户端回写需要实现推送一样的逻辑
                    socket.write(chunk);
                });
            }
            if (targetSocket.listeners('close').length === 0) {
                targetSocket.on('close', function () {
                    socket.end();
                });
            }
            /** 测试代码END */
            targetSocket.write(body);
        } else {
            console.log('not match media server');
        }
    });

    socket.on('close', function () {
        closeAllTargetSocket();
        console.log('client disconnected');
    });

    socket.on('error', function (error) {
        console.log(`error:客户端异常断开: ${error}`);
    });
});

proxy.on('error', function (err) {
    throw err;
});

proxy.listen(LOCAL_PORT, function () {
    console.log('Zone2 proxy listening on ' + LOCAL_PORT);
});