import Foundation
import XuqmCoreSDK

public final class LicenseSDK: @unchecked Sendable {

    public static let shared = LicenseSDK()

    private static let defaultBaseUrl = "https://auth.dev.xuqinmin.com/"
    private static let statusOk = "ok"
    private static let statusDenied = "denied"
    private static let cacheWindowMs: Double = 10 * 60 * 1000

    private var appKey: String?
    private var baseUrl: String = defaultBaseUrl
    private var deviceName: String?
    private let store = LicenseStore()
    private var initialized = false

    private init() {}

    /// Manual initialization. Most apps only need to place the license file at
    /// assets/xuqm/license.xuqm (bundle) and call checkLicense() — auto-init handles the rest.
    public func initialize(appKey: String, baseUrl: String? = nil, deviceName: String? = nil) {
        let url = normalize(baseUrl ?? Self.defaultBaseUrl)
        if store.appKey != nil && store.appKey != appKey { store.clear() }
        self.appKey = appKey
        self.baseUrl = url
        self.deviceName = deviceName ?? DeviceInfoProvider.getDeviceName()
        store.appKey = appKey
        initialized = true
    }

    /// Check license validity. Returns cached result within 10-minute window.
    /// On network error, falls back to last cached OK status.
    public func checkLicense(userInfo: LicenseUserInfo? = nil) async -> LicenseResult {
        if !initialized {
            await XuqmSDK.shared.awaitInitialization()
            tryAutoInitialize()
        }
        guard initialized, let appKey else {
            return .error("LicenseSDK not initialized")
        }

        let cachedStatus = store.status
        let cachedTime = store.statusTime
        if cachedStatus == Self.statusOk && (Date().timeIntervalSince1970 * 1000 - cachedTime) < Self.cacheWindowMs {
            return .success("Cached")
        }

        let deviceId = DeviceInfoProvider.getDeviceId(store: store)
        let payload = userInfo.map { UserInfoPayload(userId: $0.userId, name: $0.name, email: $0.email, phone: $0.phone) }

        do {
            if let token = store.token {
                let req = VerifyRequest(appKey: appKey, deviceId: deviceId, token: token, userInfo: payload)
                if let resp = try? await post(VerifyResponse.self, path: "api/license/verify", body: req), resp.valid {
                    persistStatus(Self.statusOk)
                    return .success("Verified")
                }
                store.token = nil
            }

            let req = RegisterRequest(
                appKey: appKey,
                deviceId: deviceId,
                deviceName: deviceName ?? DeviceInfoProvider.getDeviceName(),
                deviceModel: DeviceInfoProvider.getDeviceModel(),
                deviceVendor: DeviceInfoProvider.getDeviceVendor(),
                osVersion: DeviceInfoProvider.getOsVersion(),
                userInfo: payload
            )
            let resp = try await post(RegisterResponse.self, path: "api/license/register", body: req)
            if resp.success, let token = resp.token {
                store.token = token
                persistStatus(Self.statusOk)
                return .success("Registered")
            }
            persistStatus(Self.statusDenied)
            return .error(resp.message ?? "Registration denied")
        } catch {
            if cachedStatus == Self.statusOk { return .success("Offline - cached ok") }
            return .error(error.localizedDescription)
        }
    }

    public func getStatus() async -> LicenseStatus {
        if !initialized {
            await XuqmSDK.shared.awaitInitialization()
            tryAutoInitialize()
        }
        switch store.status {
        case Self.statusOk: return .ok
        case Self.statusDenied: return .denied
        default: return .unknown
        }
    }

    public func getDeviceId() async -> String? {
        if !initialized {
            await XuqmSDK.shared.awaitInitialization()
            tryAutoInitialize()
        }
        if !initialized { return nil }
        return store.deviceId
    }

    public func clear() { store.clear() }

    @discardableResult
    private func tryAutoInitialize() -> Bool {
        guard let file = LicenseFileReader.read(), !file.appKey.isEmpty else { return false }
        initialize(appKey: file.appKey, baseUrl: file.baseUrl)
        return true
    }

    private func persistStatus(_ status: String) {
        store.status = status
        store.statusTime = Date().timeIntervalSince1970 * 1000
    }

    private func normalize(_ url: String) -> String {
        let s = url.trimmingCharacters(in: .whitespaces)
        return s.hasSuffix("/") ? s : s + "/"
    }

    private func post<T: Decodable, B: Encodable>(_ type: T.Type, path: String, body: B) async throws -> T {
        guard let url = URL(string: baseUrl + path) else { throw URLError(.badURL) }
        var req = URLRequest(url: url)
        req.httpMethod = "POST"
        req.setValue("application/json", forHTTPHeaderField: "Content-Type")
        req.httpBody = try JSONEncoder().encode(body)
        let (data, response) = try await URLSession.shared.data(for: req)
        guard let http = response as? HTTPURLResponse, (200..<300).contains(http.statusCode) else {
            throw URLError(.badServerResponse)
        }
        guard let wrapper = try? JSONDecoder().decode(LicenseResponseWrapper<T>.self, from: data), let result = wrapper.data else {
            throw URLError(.cannotDecodeContentData)
        }
        return result
    }
}

private struct LicenseResponseWrapper<U: Decodable>: Decodable {
    let data: U?
}