import Foundation

@MainActor
final class VoxtralWebSocketClient {
    private var webSocketTask: URLSessionWebSocketTask?
    private var session: URLSession?
    private let encoder = JSONEncoder()
    private var intentionalDisconnect = false

    var onEvent: ((VoxtralEvent) -> Void)?

    func connect(apiKey: String, model: String = "voxtral-mini-transcribe-realtime-2602", delayMs: Int) {
        var components = URLComponents(string: "wss://api.mistral.ai/v1/audio/transcriptions/realtime")!
        components.queryItems = [URLQueryItem(name: "model", value: model)]
        guard let url = components.url else { return }

        var request = URLRequest(url: url)
        request.setValue("Bearer \(apiKey)", forHTTPHeaderField: "Authorization")

        let config = URLSessionConfiguration.default
        config.httpAdditionalHeaders = ["Authorization": "Bearer \(apiKey)"]
        session = URLSession(configuration: config)
        webSocketTask = session?.webSocketTask(with: request)
        webSocketTask?.resume()

        intentionalDisconnect = false
        // Start receiving first, then send session config
        receiveLoop()

        // Send session config after connection
        let sessionConfig = SessionUpdateMessage(
            session: SessionConfig(
                audioFormat: AudioFormatConfig(),
                targetStreamingDelayMs: delayMs
            )
        )
        sendJSON(sessionConfig)
    }

    func sendAudio(_ pcmData: Data) {
        let base64 = pcmData.base64EncodedString()
        let msg = AudioAppendMessage(audio: base64)
        sendJSON(msg)
    }

    func flush() {
        sendJSON(AudioFlushMessage())
    }

    func ping() {
        webSocketTask?.sendPing { error in
            if let error {
                print("[MyVoxtral] Ping failed: \(error.localizedDescription)")
            }
        }
    }

    func disconnect() {
        intentionalDisconnect = true
        sendJSON(AudioEndMessage())
        webSocketTask?.cancel(with: .normalClosure, reason: nil)
        webSocketTask = nil
        session?.invalidateAndCancel()
        session = nil
    }

    private func sendJSON<T: Encodable>(_ value: T) {
        guard let data = try? encoder.encode(value),
              let string = String(data: data, encoding: .utf8) else { return }
        webSocketTask?.send(.string(string)) { error in
            if let error {
                print("WebSocket send error: \(error)")
            }
        }
    }

    private func receiveLoop() {
        webSocketTask?.receive { [weak self] result in
            switch result {
            case .success(let message):
                switch message {
                case .string(let text):
                    if let data = text.data(using: .utf8) {
                        let event = parseVoxtralEvent(from: data)
                        Task { @MainActor in
                            self?.onEvent?(event)
                        }
                    }
                case .data(let data):
                    let event = parseVoxtralEvent(from: data)
                    Task { @MainActor in
                        self?.onEvent?(event)
                    }
                @unknown default:
                    break
                }
                Task { @MainActor in self?.receiveLoop() }
            case .failure(let error):
                Task { @MainActor in
                    guard let self, !self.intentionalDisconnect else { return }
                    self.onEvent?(.error("Connection lost: \(error.localizedDescription)"))
                }
            }
        }
    }
}