/*
 * simcu::websocket.client —— 事件回调式 WebSocket 客户端（RFC 6455）。
 *
 * 用法：
 *   let client = WebSocketClient("127.0.0.1", 8080)
 *   client.onOpen = { println("已连接") }
 *   client.onMessage = { (m) => println(m.text) }
 *   client.onClose = { (code, reason) => println("关闭: ${code} ${reason}") }
 *   client.connect()
 *   client.sendText("hello")
 *   client.close()   // 或 client.terminate() 立即断开
 *
 * 说明：
 *   - connect() 抛出的异常表示握手失败；连接建立后的错误走 onError。
 *   - close(code, reason) 发起 RFC 6455 关闭握手（等待对端回 close 帧，5 秒兜底）；
 *     terminate() 直接断开底层连接。
 *   - 回调在后台读线程触发，禁止在回调中直接做耗时操作。
 */
package simcu::websocket.client

import std.net.TcpSocket
import std.time.*
import std.sync.Mutex

import simcu::websocket.common.FrameStream
import simcu::websocket.common.MessageType
import simcu::websocket.common.ReadyState
import simcu::websocket.common.WebSocketMessage
import simcu::websocket.common.WebSocketException

/// 事件回调式 WebSocket 客户端。
public class WebSocketClient {
    private let host: String
    private let port: UInt16
    private let path: String
    private let maxPayload: Int64
    private var frame: ?FrameStream = None
    private var state: ReadyState = ReadyState.Closed
    private let stateLock = Mutex()

    /// 连接建立（握手完成）后触发，无参数。
    public var onOpen: () -> Unit = { => () }
    /// 收到文本/二进制消息时触发，参数为消息。
    public var onMessage: (WebSocketMessage) -> Unit = { m => () }
    /// 连接建立后的运行时错误触发，参数为异常。
    public var onError: (Exception) -> Unit = { e => () }
    /// 连接关闭时触发，参数为 (关闭码, 关闭原因)。
    public var onClose: (Int64, String) -> Unit = { c, r => () }

    /// @param host 服务端主机（IP 或域名）。
    /// @param port 服务端端口。
    /// @param path 请求路径，默认 "/"。
    /// @param maxPayload 单条消息最大字节数，默认 64KB，超出触发 onError(code=1009)。
    public init(host: String, port: UInt16, path!: String = "/", maxPayload!: Int64 = 65536) {
        this.host = host
        this.port = port
        this.path = path
        this.maxPayload = maxPayload
    }

    /// 当前连接状态（Connecting/Open/Closing/Closed）。
    public prop readyState: ReadyState {
        get() { state }
    }

    /// 连接是否处于 Open。
    public func isOpen(): Bool {
        state == ReadyState.Open
    }

    /// 建立连接：TCP + WebSocket 握手。
    /// 成功 → 状态 Open 并触发 onOpen，随后后台线程持续读取消息。
    /// 失败（网络/握手被拒）→ 抛出 WebSocketException。
    public func connect(timeout!: ?Duration = None): Unit {
        if (state != ReadyState.Closed) {
            throw WebSocketException("重复 connect：当前 readyState=${state}")
        }
        state = ReadyState.Connecting
        let sock = TcpSocket(host, port)
        sock.connect(timeout: timeout)
        let fs = FrameStream(sock, maxPayload, true)

        // 发送握手请求
        let key = FrameStream.generateWebSocketKey()
        let req = StringBuilder()
        req.append("GET ${path} HTTP/1.1\r\n")
        req.append("Host: ${host}:${port}\r\n")
        req.append("Upgrade: websocket\r\n")
        req.append("Connection: Upgrade\r\n")
        req.append("Sec-WebSocket-Key: ${key}\r\n")
        req.append("Sec-WebSocket-Version: 13\r\n\r\n")
        sock.write(req.toString().toArray())
        sock.flush()

        // 读取并校验握手响应
        let response = fs.readHttpHeader()
        if (!validateHandshake(response, key)) {
            fs.close()
            sock.close()
            state = ReadyState.Closed
            throw WebSocketException("WebSocket 握手失败（服务端拒绝升级）")
        }

        frame = Some(fs)
        state = ReadyState.Open
        onOpen()
        spawn { => readLoop() }
    }

    /// 发送消息（按消息类型自动选择 text/binary 帧）。
    public func send(message: WebSocketMessage): Unit {
        let f = frame.getOrThrow()
        if (message.`type` == MessageType.Text) {
            f.writeFrame(1, message.bytes)
        } else {
            f.writeFrame(2, message.bytes)
        }
    }

    /// 发送文本消息。
    public func sendText(text: String): Unit {
        frame.getOrThrow().writeText(text)
    }

    /// 发送二进制消息。
    public func sendBinary(data: Array<Byte>): Unit {
        frame.getOrThrow().writeBinary(data)
    }

    /// 发送 Ping（心跳保活），对端 Pong 由帧层自动忽略。
    public func ping(): Unit {
        frame.getOrThrow().writePing(Array<Byte>(0, repeat: 0))
    }

    /// 发送 Ping（携带 payload）。
    public func ping(payload: Array<Byte>): Unit {
        frame.getOrThrow().writePing(payload)
    }

    /// 发起关闭握手：发送 close 帧（code + reason），等待对端回执后触发 onClose。
    /// 对端 5 秒内不回执则强制断开。
    public func close(code!: Int64 = 1000, reason!: String = ""): Unit {
        synchronized(stateLock) {
            if (state != ReadyState.Open) {
                return
            }
            state = ReadyState.Closing
        }
        if (let Some(f) <- frame) {
            try {
                f.writeClose(code, reason)
            } catch (_) {
                terminate()
                return
            }
        }
        spawn { =>
            sleep(Duration.second * 5)
            if (state == ReadyState.Closing) {
                terminate()
            }
        }
    }

    /// 立即断开底层连接（不发送 close 帧），读线程会触发 onClose(1006, "")。
    public func terminate(): Unit {
        synchronized(stateLock) {
            if (state == ReadyState.Closed) {
                return
            }
            state = ReadyState.Closed
        }
        if (let Some(f) <- frame) {
            try {
                f.close()
            } catch (_) {
                ()
            }
        }
    }

    /// 后台读循环：数据帧 → onMessage；close 帧 → 回执并 onClose；EOF/异常 → onError(仅异常)+onClose。
    private func readLoop(): Unit {
        var code: Int64 = 1006
        var reason: String = ""
        try {
            while (true) {
                let m = frame.getOrThrow().readMessage()
                match (m) {
                    case None =>
                        break // EOF：对端直接断连
                    case Some(f) =>
                        if (f.opcode == 8) {
                            let (c, r) = FrameStream.parseClosePayload(f.payload)
                            code = c
                            reason = r
                            if (state == ReadyState.Open) {
                                try {
                                    frame.getOrThrow().writeClose(c, r)
                                } catch (_) {
                                    ()
                                }
                            }
                            break
                        } else {
                            let msg = if (f.opcode == 1) {
                                WebSocketMessage(MessageType.Text, f.payload)
                            } else {
                                WebSocketMessage(MessageType.Binary, f.payload)
                            }
                            onMessage(msg)
                        }
                }
            }
        } catch (e: Exception) {
            code = 1006
            if (state != ReadyState.Closing) {
                onError(e)
            }
        }
        synchronized(stateLock) {
            state = ReadyState.Closed
        }
        if (let Some(f) <- frame) {
            try {
                f.close()
            } catch (_) {
                ()
            }
        }
        onClose(code, reason)
    }

    /// 校验服务端握手响应：状态行 101 + Upgrade/Connection/Accept 头。
    private func validateHandshake(response: String, key: String): Bool {
        if (!response.startsWith("HTTP/1.1 101")) {
            return false
        }
        let expected = FrameStream.computeAccept(key)
        var foundUpgrade = false
        var foundAccept = false
        let lines = response.split("\r\n")
        for (line in lines) {
            let ci = line.indexOf(":")
            if (let Some(c) <- ci) {
                let name = line[0..c].toAsciiLower()
                let value = line[c + 1..].trimAscii()
                if (name == "upgrade" && value.toAsciiLower().contains("websocket")) {
                    foundUpgrade = true
                }
                if (name == "sec-websocket-accept" && value == expected) {
                    foundAccept = true
                }
            }
        }
        foundUpgrade && foundAccept
    }
}