//
//  SDLSuperClient.swift
//  Tun
//
//  Created by 安礼成 on 2026/2/13.
//

import Foundation
import Network

final class SDLSuperClient: @unchecked Sendable {
    private let queue = DispatchQueue(label: "com.sdl.SuperClient.queue") // 专用队列保证线程安全
    // 数据流
    public let messageStream: AsyncThrowingStream<SDLSuperMessage, Error>
    private let messageCont: AsyncThrowingStream<SDLSuperMessage, Error>.Continuation
    
    private let stateLock = NSLock()
    private var isStarted = false
    private var isStopped = false
    private var isMessageContinuationFinished = false

    private let connection: NWConnection
    private let maxBufferSize: Int
    
    init(serverEndpoint: SDLConfiguration.ResolvedServerEndpoint, port: UInt16, maxBufferSize: Int = 2 * 1024 * 1024) {
        self.maxBufferSize = maxBufferSize
        
        let pairs = AsyncThrowingStream.makeStream(of: SDLSuperMessage.self)
        self.messageStream = pairs.stream
        self.messageCont = pairs.continuation
        
        let options = NWProtocolTLS.Options()
        serverEndpoint.host.withCString {
            sec_protocol_options_set_tls_server_name(options.securityProtocolOptions, $0)
        }
        sec_protocol_options_add_tls_application_protocol(
            options.securityProtocolOptions,
            "punchnet/1.0"
        )
        
        // 这里设置证书的校验逻辑
        sec_protocol_options_set_verify_block(
            options.securityProtocolOptions,
            { _, trust, complete in
                // 执行公钥校验
                complete(SDLSuperTLSVerifier.verify(trust: trust, host: serverEndpoint.host))
            },
            queue
        )
        
        let params = NWParameters(tls: options)
        // 关键：让 Network.framework 忽略系统代理
        params.preferNoProxies = true
        
        self.connection = NWConnection(host: Self.makeEndpointHost(address: serverEndpoint.ip), port: .init(rawValue: port)!, using: params)
        
        SDLLogger.log("[SDLSuperClient] start with tls protocol", category: .super)
    }
    
    func run() async throws {
        guard self.markStarted() else {
            return
        }

        let stateStream = self.makeStateStream()
        defer {
            self.stop()
        }

        try await withTaskCancellationHandler {
            self.connection.start(queue: self.queue)
            try await self.waitUntilReady(stateStream)
            try await self.readLoop()
        } onCancel: {
            self.connection.cancel()
        }
    }

    private static func makeEndpointHost(address ip: String) -> NWEndpoint.Host {
        if let ipv4Address = IPv4Address(ip) {
            return .ipv4(ipv4Address)
        }

        if let ipv6Address = IPv6Address(ip) {
            return .ipv6(ipv6Address)
        }

        preconditionFailure("invalid super server IP: \(ip)")
    }

    private func makeStateStream() -> AsyncThrowingStream<NWConnection.State, Error> {
        let connection = self.connection
        return AsyncThrowingStream(bufferingPolicy: .bufferingNewest(16)) { continuation in
            connection.stateUpdateHandler = { [weak self] state in
                SDLLogger.log("[SDLSuperClient] new state: \(state)", category: .super)
                switch state {
                case .failed(let error):
                    let wrappedError = SDLSuperError.connectionFailed(error)
                    self?.finishMessageStream(throwing: wrappedError)
                    continuation.finish(throwing: wrappedError)
                case .cancelled:
                    self?.finishMessageStream(throwing: SDLSuperError.connectionCancelled)
                    continuation.finish(throwing: SDLSuperError.connectionCancelled)
                default:
                    continuation.yield(state)
                }
            }
        }
    }

    private func waitUntilReady(_ stateStream: AsyncThrowingStream<NWConnection.State, Error>) async throws {
        for try await state in stateStream {
            try Task.checkCancellation()

            if case .ready = state {
                return
            }
        }

        throw SDLSuperError.connectionCancelled
    }

    private func readLoop() async throws {
        let frameParser = SDLSuperFrameParser(maxBufferSize: self.maxBufferSize)
        while true {
            try Task.checkCancellation()
            let data = try await Self.readOnce(connection: self.connection)
            let frames = try frameParser.parseFrames(data: data)
            for frame in frames {
                try Task.checkCancellation()
                if let message = SDLSuperCodec.decode(frame: frame) {
                    self.messageCont.yield(message)
                } else {
                    throw SDLSuperError.decodeError("invalid message")
                }
            }
        }
    }
    
    func send(type: SDLPacketType, data: Data) {
        guard connection.state == .ready else {
            return
        }
        
        var len = UInt16(data.count + 1).bigEndian
        var packet = Data(Data(bytes: &len, count: 2))
        packet.append(type.rawValue)
        packet.append(data)
        
        connection.send(content: packet, completion: .contentProcessed { [weak self] error in
            if let error {
                SDLLogger.log("[SDLSuperClient] send data get error: \(error)", category: .super)
                self?.finishMessageStream(throwing: SDLSuperError.writeFailed(error))
            }
        })
    }
    
    private static func readOnce(connection: NWConnection) async throws -> Data {
        guard connection.state == .ready else {
            throw SDLSuperError.connectionCancelled
        }
        
        let readContinuation = OnceContinuation<Data, Error>()
        
        return try await withTaskCancellationHandler {
            try await withCheckedThrowingContinuation { cont in
                readContinuation.set(cont)
                connection.receive(minimumIncompleteLength: 1, maximumLength: 64 * 1024) { data, _, isComplete, error in
                    if let error {
                        readContinuation.resume(throwing: error)
                        return
                    }
                    
                    if isComplete {
                        readContinuation.resume(throwing: SDLSuperError.dataStreamClosed)
                    } else {
                        readContinuation.resume(returning: data ?? Data())
                    }
                }
            }
        } onCancel: {
            readContinuation.resume(throwing: CancellationError())
        }
    }
    
    func stop() {
        guard self.markStopped() else {
            return
        }

        let connection = self.connection
        connection.stateUpdateHandler = nil
        connection.cancel()
        self.finishMessageStream()
        
        SDLLogger.log("[SDLSuperClient] stopped", category: .super)
    }

    private func markStarted() -> Bool {
        self.stateLock.lock()
        defer {
            self.stateLock.unlock()
        }

        guard !self.isStarted, !self.isStopped else {
            return false
        }

        self.isStarted = true
        return true
    }

    private func markStopped() -> Bool {
        self.stateLock.lock()
        defer {
            self.stateLock.unlock()
        }

        guard !self.isStopped else {
            return false
        }

        self.isStopped = true
        return true
    }

    private func finishMessageStream(throwing error: Error? = nil) {
        self.stateLock.lock()
        let shouldFinish = !self.isMessageContinuationFinished
        if shouldFinish {
            self.isMessageContinuationFinished = true
        }
        self.stateLock.unlock()

        guard shouldFinish else {
            return
        }

        if let error {
            self.messageCont.finish(throwing: error)
        } else {
            self.messageCont.finish()
        }
    }
    
    deinit {
        SDLLogger.log("[SDLSuperClient] deinit", category: .super)
    }
    
}