package com.lanremote.watch;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketTimeoutException;
import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.Map;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.TimeUnit;

/**
 * 被控端协议客户端（纯 Java，无 Android 依赖）。
 *
 * 之所以保持纯 Java：可以把它编译到桌面 JVM，直接连真实的 Python 被控端做联调，
 * 而不是只靠"看起来应该没问题"。
 */
public class RemoteClient {

    public static final Charset UTF8 = Charset.forName("UTF-8");
    public static final int CHUNK_SIZE = 256 * 1024;
    public static final int DEFAULT_PORT = 8765;

    /** 事件与断开回调。注意：回调发生在读取线程，UI 层需自行切主线程。 */
    public interface Listener {
        void onEvent(String event, Map<String, Object> message);

        void onDisconnected(String reason);
    }

    /**
     * 传输层。局域网直连时是 SocketTransport，跨网络时是 RelayTransport。
     * 抽出来之后协议逻辑完全不用管数据是走 TCP 还是走中转的 HTTPS。
     */
    private Transport transport;
    private BufferedReader reader;
    private OutputStream writer;
    private Thread readerThread;
    /** 单行上限，和服务端的 MAX_LINE_BYTES 对齐 */
    private static final int MAX_LINE_CHARS = 8 * 1024 * 1024;

    private volatile boolean running;

    private final BlockingQueue<Map<String, Object>> replies =
            new LinkedBlockingQueue<Map<String, Object>>();
    private final Object sendLock = new Object();

    private Listener listener;
    private String serverName = "";
    private String deviceId = "";
    private String deviceName = "手表";

    // ------------------------------------------------------------------

    public boolean isConnected() {
        return running && transport != null && !transport.isClosed();
    }

    /** 当前传输方式的描述，界面上用来显示"直连"还是"经中转"。 */
    public String transportName() {
        if (transport == null) {
            return "";
        }
        return transport instanceof RelayTransport ? "中转" : "直连";
    }

    public RelayTransport relayTransport() {
        return transport instanceof RelayTransport
                ? (RelayTransport) transport : null;
    }

    public String getServerName() {
        return serverName;
    }

    public void setDevice(String deviceId, String deviceName) {
        this.deviceId = deviceId == null ? "" : deviceId;
        this.deviceName = deviceName == null ? "手表" : deviceName;
    }

    // ------------------------------------------------------------------
    // 连接与握手
    // ------------------------------------------------------------------

    /**
     * 连接并完成握手。
     *
     * @param token 为空则用配对码配对；非空则直接令牌登录（下次打开免配对码）
     * @return 服务端握手回包，含 ok / token / serverName
     */
    public Map<String, Object> connect(String host, int port, String code, String token,
                                       Listener listener, int timeoutMs) throws IOException {
        close();
        this.listener = listener;
        this.running = true;
        this.replies.clear();

        Socket sock = new Socket();
        sock.connect(new InetSocketAddress(host, port), timeoutMs);
        sock.setSoTimeout(0);
        sock.setTcpNoDelay(true);
        return startTransport(new Transport.SocketTransport(sock), code, token,
                listener, timeoutMs);
    }

    /**
     * 经中转服务器连接（跨网络）。
     *
     * 手表没法直连电脑（两边都在 NAT 后面），所以两边都主动连出去，
     * 由中转按配对码把两条连接对上。中转只转发字节、不认识协议内容，
     * 所以电脑那边的配对和令牌校验照样生效。
     */
    /** 上次经中转接入时，被控端报的局域网 IP 和端口。 */
    private java.util.List<String> relayLanIps = new java.util.ArrayList<String>();
    private int relayLanPort;

    public java.util.List<String> relayLanIps() {
        return relayLanIps;
    }

    public int relayLanPort() {
        return relayLanPort;
    }

    public Map<String, Object> connectViaRelay(String baseUrl, String code,
                                               String token, Listener listener,
                                               int timeoutMs) throws IOException {
        close();
        relayLanIps = new java.util.ArrayList<String>();
        relayLanPort = 0;
        RelayTransport relay = new RelayTransport(baseUrl, code, deviceName);
        if (!relay.attach()) {
            String reason = relay.getLastError();
            if (reason == null || reason.isEmpty()) {
                reason = "连不上中转服务器";
            }
            relay.close();
            // 和局域网那条路保持一致：握手被拒要回 ok=false，不要抛异常。
            // 抛异常的话界面只能显示"连不上"，分不清是配对码错了、
            // 设备不在线、还是中转服务器连不上 —— 这三者的处理方式完全不同。
            this.serverName = "";
            return Json.obj("ok", false, "error", reason);
        }
        Map<String, Object> reply =
                startTransport(relay, code, token, listener, timeoutMs);
        if (Json.bool(reply, "ok", false)) {
            // 留给界面判断：要不要切成局域网直连
            relayLanIps = relay.getLanIps();
            relayLanPort = relay.getLanPort();
        }
        return reply;
    }

    /** 握手 + 起读取线程。局域网和中转共用这一段。 */
    private Map<String, Object> startTransport(Transport channel, String code,
                                               String token, Listener listener,
                                               int timeoutMs) throws IOException {
        this.listener = listener;
        this.running = true;
        this.replies.clear();
        this.transport = channel;
        this.reader = new BufferedReader(
                new InputStreamReader(channel.input(), UTF8), 8192);
        this.writer = channel.output();

        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                readLoop();
            }
        }, "lanremote-reader");
        thread.setDaemon(true);
        thread.start();
        this.readerThread = thread;

        Map<String, Object> handshake;
        if (token != null && token.length() > 0) {
            handshake = Json.obj("cmd", "auth", "deviceId", deviceId,
                    "deviceName", deviceName, "token", token);
        } else {
            handshake = Json.obj("cmd", "pair", "deviceId", deviceId,
                    "deviceName", deviceName, "code", code == null ? "" : code.trim());
        }

        Map<String, Object> reply;
        try {
            reply = call(handshake, timeoutMs);
        } catch (IOException failed) {
            // 握手失败必须关掉，否则 socket 和读取线程泄漏，
            // 而且 isConnected() 会一直是 true，界面以为连上了。
            close();
            throw failed;
        }
        if (Json.bool(reply, "ok", false)) {
            this.serverName = Json.str(reply, "serverName", "");
        } else {
            close();
        }
        return reply;
    }

    public void close() {
        running = false;
        try {
            if (transport != null) {
                transport.close();
            }
        } catch (Exception ignored) {
            // 关闭时的异常无需处理
        }
        transport = null;
        reader = null;
        writer = null;
        replies.clear();
    }

    // ------------------------------------------------------------------
    // 收发
    // ------------------------------------------------------------------

    private void readLoop() {
        try {
            // close() 会把 reader 置 null，而 running 判断和 readLine 之间有竞态。
            // 先取到局部变量并判空，避免 NPE —— 读取线程里的未捕获 NPE 会杀掉整个进程。
            BufferedReader localReader = this.reader;
            if (localReader == null) {
                return;
            }
            String line;
            while (running && (line = localReader.readLine()) != null) {
                if (line.length() > MAX_LINE_CHARS) {
                    continue;             // 对端发超长单行，直接丢弃防止占满内存
                }
                if (line.trim().isEmpty()) {
                    continue;
                }
                Map<String, Object> message;
                try {
                    message = Json.parseObject(line);
                } catch (Exception malformed) {
                    continue;             // 单条报文损坏不影响整条连接
                }
                if (message.containsKey("event")) {
                    if (listener != null) {
                        listener.onEvent(String.valueOf(message.get("event")), message);
                    }
                } else {
                    replies.offer(message);
                }
            }
        } catch (IOException ignored) {
            // 连接被关闭或网络中断，走下面的统一处理
        } finally {
            boolean notify = running;
            running = false;
            if (notify && listener != null) {
                listener.onDisconnected("连接已断开");
            }
        }
    }

    private void send(Map<String, Object> message) throws IOException {
        OutputStream out = writer;
        if (out == null) {
            throw new IOException("尚未连接");
        }
        byte[] payload = (Json.write(message) + "\n").getBytes(UTF8);
        synchronized (sendLock) {
            out.write(payload);
            out.flush();
        }
    }

    /** 发一条命令并等待应答。 */
    public Map<String, Object> call(Map<String, Object> message, long timeoutMs)
            throws IOException {
        if (!isConnected()) {
            throw new IOException("尚未连接");
        }
        send(message);
        return awaitReply(timeoutMs);
    }

    private Map<String, Object> awaitReply(long timeoutMs) throws IOException {
        try {
            Map<String, Object> reply = replies.poll(timeoutMs, TimeUnit.MILLISECONDS);
            if (reply == null) {
                throw new SocketTimeoutException("等待服务端响应超时");
            }
            return reply;
        } catch (InterruptedException interrupted) {
            Thread.currentThread().interrupt();
            throw new IOException("等待响应被中断");
        }
    }

    public Map<String, Object> sendString(String cmd, String key, String value, long timeoutMs)
            throws IOException {
        Map<String, Object> message = Json.obj("cmd", cmd);
        message.put(key, value);
        return call(message, timeoutMs);
    }

    // ------------------------------------------------------------------
    // 分块传输（图片 / 音频 / 文件）
    // ------------------------------------------------------------------

    public Map<String, Object> sendChunks(String cmd, String name, byte[] blob, long timeoutMs)
            throws IOException {
        int total = blob.length == 0 ? 1 : (blob.length + CHUNK_SIZE - 1) / CHUNK_SIZE;
        for (int index = 0; index < total; index++) {
            int from = index * CHUNK_SIZE;
            int to = Math.min(blob.length, from + CHUNK_SIZE);
            byte[] piece = blob.length == 0 ? new byte[0] : Arrays.copyOfRange(blob, from, to);
            Map<String, Object> message = Json.obj(
                    "cmd", cmd,
                    "name", name,
                    "seq", index,
                    "last", index == total - 1,
                    "data", B64.encode(piece));
            send(message);
        }
        return awaitReply(timeoutMs);
    }

    // ------------------------------------------------------------------
    // 便捷封装
    // ------------------------------------------------------------------

    public boolean ping(long timeoutMs) {
        try {
            return Json.bool(call(Json.obj("cmd", "ping"), timeoutMs), "pong", false);
        } catch (IOException e) {
            return false;
        }
    }
}