import Foundation

@MainActor
public final class XuqmSDK: NSObject {

    public static let shared = XuqmSDK()
    private(set) var config: SDKConfig?
    private(set) var tokenStore: TokenStore?

    public private(set) var currentUserId: String?
    public var onUserSigExpired: (() -> Void)?

    private var userSig: String?
    private var userSigTimer: Timer?
    private var cachedDeviceToken: String?

    private override init() {
        super.init()
    }

    public func initialize(config: SDKConfig) {
        self.config = config
        self.tokenStore = TokenStore()
        ApiClient.shared.configure(with: config)
    }

    public func requireConfig() -> SDKConfig {
        guard let config else {
            fatalError("XuqmSDK not initialized. Call XuqmSDK.shared.initialize() first.")
        }
        return config
    }

    public func login(userId: String, userSig: String) async {
        self.currentUserId = userId
        self.userSig = userSig
        startUserSigExpirationTimer(userSig: userSig)

        do {
            try await ImSDK.shared.loginWithUserSig(userId, userSig)
        } catch {
            // IM login failed; silently ignored per facade pattern
        }

        if let cachedDeviceToken {
            do {
                try await PushSDK.shared.registerToken(cachedDeviceToken, userId: userId)
            } catch {
                // Push registration failed
            }
        }
    }

    public func logout() async {
        userSigTimer?.invalidate()
        userSigTimer = nil

        ImSDK.shared.disconnect()

        if let userId = currentUserId {
            do {
                try await PushSDK.shared.unregisterToken(userId: userId)
            } catch {
                // Push unregistration failed
            }
        }

        tokenStore?.clear()
        currentUserId = nil
        userSig = nil
        cachedDeviceToken = nil
    }

    public func registerDeviceToken(_ deviceToken: Data) {
        let token = deviceToken.map { String(format: "%02x", $0) }.joined()
        self.cachedDeviceToken = token
        Task { @MainActor in
            if let userId = self.currentUserId {
                try? await PushSDK.shared.registerToken(token, userId: userId)
            }
        }
    }

    private func startUserSigExpirationTimer(userSig: String) {
        userSigTimer?.invalidate()
        guard let expDate = extractExpirationDate(from: userSig) else { return }
        let interval = expDate.timeIntervalSinceNow - 300 // 5 minutes before expiry
        guard interval > 0 else {
            onUserSigExpired?()
            return
        }
        userSigTimer = Timer.scheduledTimer(
            timeInterval: interval,
            target: self,
            selector: #selector(userSigDidExpire),
            userInfo: nil,
            repeats: false
        )
    }

    @objc private func userSigDidExpire() {
        onUserSigExpired?()
    }

    private func extractExpirationDate(from userSig: String) -> Date? {
        let parts = userSig.split(separator: ".")
        guard parts.count >= 2 else { return nil }
        var base64 = String(parts[1])
            .replacingOccurrences(of: "-", with: "+")
            .replacingOccurrences(of: "_", with: "/")
        let padding = 4 - base64.count % 4
        if padding != 4 {
            base64 += String(repeating: "=", count: padding)
        }
        guard let data = Data(base64Encoded: base64),
              let json = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
              let exp = json["exp"] as? TimeInterval else {
            return nil
        }
        return Date(timeIntervalSince1970: exp)
    }
}