import Foundation
import UserNotifications
import UIKit

enum NotificationService {
    @MainActor
    static func requestPermission() async {
        _ = try? await UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .sound, .badge])
        UIApplication.shared.registerForRemoteNotifications()
    }

    @MainActor private static var deviceToken: String?
    @MainActor private static var registeredSession: String?

    @MainActor
    static func receivedDeviceToken(_ data: Data) async {
        deviceToken = data.map { String(format: "%02x", $0) }.joined()
        registeredSession = nil
        await syncPushRegistration()
    }

    @MainActor
    static func syncPushRegistration() async {
        let session = KeychainStore.load()
        guard !session.isEmpty, let deviceToken, registeredSession != session else { return }
        let environment = Bundle.main.object(forInfoDictionaryKey: "KASZTELANPushEnvironment") as? String ?? "production"
        do {
            try await APIClient().registerPush(deviceToken: deviceToken, environment: environment, token: session)
            // The account may have changed while the request was in flight.
            if KeychainStore.load() == session { registeredSession = session }
        } catch {
            // Retry when the app next refreshes; keep account access working offline.
        }
    }

    @MainActor
    static func unregisterPush(session: String) async {
        registeredSession = nil
        guard let deviceToken else { return }
        try? await APIClient().unregisterPush(deviceToken: deviceToken, token: session)
    }

    static func recordReceivedPush(_ content: UNNotificationContent) {
        guard let id = content.userInfo["message_id"] as? Int, id > 0 else { return }
        var received = UserDefaults.standard.array(forKey: "kasztelan.push.receivedIDs") as? [Int] ?? []
        received.removeAll { $0 == id }
        received.append(id)
        UserDefaults.standard.set(Array(received.suffix(100)), forKey: "kasztelan.push.receivedIDs")
    }

    static func show(_ message: KasztelanMessage) async {
        let received = UserDefaults.standard.array(forKey: "kasztelan.push.receivedIDs") as? [Int] ?? []
        guard !received.contains(message.id) else { return }
        let settings = await UNUserNotificationCenter.current().notificationSettings()
        guard settings.authorizationStatus == .authorized || settings.authorizationStatus == .provisional else { return }
        let delivered = await UNUserNotificationCenter.current().deliveredNotifications()
        guard !delivered.contains(where: {
            ($0.request.content.userInfo["message_id"] as? Int) == message.id
        }) else { return }
        let content = UNMutableNotificationContent()
        content.title = "KASZTELAN"
        content.subtitle = message.title
        content.body = message.text
        content.sound = .default
        content.threadIdentifier = "kasztelan-messages"
        content.categoryIdentifier = "KASZTELAN_MESSAGE"
        content.userInfo = ["message_id": message.id]
        let request = UNNotificationRequest(identifier: "kasztelan-\(message.id)", content: content, trigger: nil)
        try? await UNUserNotificationCenter.current().add(request)
    }
}