import Foundation

public final class ImClient: NSObject, URLSessionWebSocketDelegate, @unchecked Sendable {

    public weak var delegate: ImEventDelegate?
    private var webSocketTask: URLSessionWebSocketTask?
    private var session: URLSession?
    private let wsURL: URL
    private let token: String
    private let appId: String
    private var shouldReconnect = false

    public init(wsURL: URL, token: String, appId: String) {
        self.wsURL = wsURL
        self.token = token
        self.appId = appId
        super.init()
    }

    public func connect() {
        shouldReconnect = true
        var request = URLRequest(url: wsURL)
        request.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
        session = URLSession(configuration: .default, delegate: self, delegateQueue: nil)
        webSocketTask = session?.webSocketTask(with: request)
        webSocketTask?.resume()
        receiveMessage()
    }

    private func receiveMessage() {
        webSocketTask?.receive { [weak self] result in
            switch result {
            case .success(let message):
                if case .string(let text) = message {
                    self?.handleMessage(text)
                }
                self?.receiveMessage()
            case .failure(let error):
                self?.delegate?.imClientDidError(error.localizedDescription)
            }
        }
    }

    private func handleMessage(_ text: String) {
        guard let data = text.data(using: .utf8),
              let msg = try? JSONDecoder().decode(ImMessage.self, from: data) else { return }
        if msg.chatType == .group {
            delegate?.imClientDidReceiveGroupMessage(msg)
        } else {
            delegate?.imClientDidReceiveMessage(msg)
        }
    }

    public func sendMessage(toId: String, chatType: ChatType, msgType: MsgType, content: String) {
        let payload: [String: Any] = [
            "type": "chat.send",
            "data": ["appId": appId, "toId": toId, "chatType": chatType.rawValue,
                     "msgType": msgType.rawValue, "content": content]
        ]
        guard let data = try? JSONSerialization.data(withJSONObject: payload),
              let text = String(data: data, encoding: .utf8) else { return }
        webSocketTask?.send(.string(text)) { _ in }
    }

    public func disconnect() {
        shouldReconnect = false
        webSocketTask?.cancel(with: .normalClosure, reason: nil)
    }

    public func urlSession(_ session: URLSession, webSocketTask: URLSessionWebSocketTask,
                           didOpenWithProtocol protocol: String?) {
        delegate?.imClientDidConnect()
    }

    public func urlSession(_ session: URLSession, webSocketTask: URLSessionWebSocketTask,
                           didCloseWith closeCode: URLSessionWebSocketTask.CloseCode, reason: Data?) {
        let reasonStr = reason.flatMap { String(data: $0, encoding: .utf8) }
        delegate?.imClientDidDisconnect(reason: reasonStr)
    }
}