// NotificationManager.swift
// Jarvis — local notifications: morning/evening briefings (weather + top signal
// stories) and breaking-story alerts. Refreshes briefing content on foreground and
// via a background-refresh task.
//
// iOS limit: local notifications carry the content set at *schedule* time. We keep
// them reasonably fresh by rebuilding on foreground + background refresh. Truly live
// pushes while the app is closed would need a push server (APNs / ntfy) — see
// docs/BACKLOG.md.

import Foundation
import Combine
import UserNotifications
import BackgroundTasks

enum BriefingPeriod { case morning, evening
    var greeting: String { self == .morning ? "Good morning" : "Good evening" }
    var emoji: String { self == .morning ? "☀️" : "🌙" }
    var requestID: String { self == .morning ? "briefing.morning" : "briefing.evening" }
}

/// Background-refresh task identifier (also declared in Info.plist
/// BGTaskSchedulerPermittedIdentifiers and registered in AppDelegate).
let jarvisBriefingRefreshID = "com.kisani.jarvis.briefing.refresh"

@MainActor
final class NotificationManager: NSObject, ObservableObject {
    static let shared = NotificationManager()

    @Published var authStatus: UNAuthorizationStatus = .notDetermined

    private let center = UNUserNotificationCenter.current()
    private let settings = NotificationSettings.shared
    private let api = APIClient.shared
    private var cancellables = Set<AnyCancellable>()

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

    // MARK: - Lifecycle

    func bootstrap() async {
        center.delegate = self
        await refreshAuthStatus()
        subscribeToBreakingEvents()
        await applySettings()
    }

    // MARK: - Authorization

    func refreshAuthStatus() async {
        authStatus = await center.notificationSettings().authorizationStatus
    }

    @discardableResult
    func requestAuthorization() async -> Bool {
        let granted = (try? await center.requestAuthorization(options: [.alert, .sound, .badge])) ?? false
        settings.enabled = granted
        await refreshAuthStatus()
        if granted { await applySettings() }
        return granted
    }

    private var isAuthorized: Bool { authStatus == .authorized || authStatus == .provisional }

    // MARK: - Apply settings (reschedule everything)

    func applySettings() async {
        guard settings.enabled, isAuthorized else {
            center.removePendingNotificationRequests(withIdentifiers: [
                BriefingPeriod.morning.requestID, BriefingPeriod.evening.requestID])
            return
        }
        await resolveLocationIfNeeded()
        await scheduleBriefings()
        scheduleBackgroundRefresh()
    }

    private func resolveLocationIfNeeded() async {
        guard settings.weatherEnabled, !settings.locationName.isEmpty,
              !settings.hasResolvedLocation else { return }
        if let geo = await WeatherService.geocode(settings.locationName) {
            settings.latitude = geo.latitude
            settings.longitude = geo.longitude
            settings.resolvedPlace = [geo.name, geo.country].compactMap { $0 }.joined(separator: ", ")
        }
    }

    // MARK: - Briefings

    func scheduleBriefings() async {
        center.removePendingNotificationRequests(withIdentifiers: [
            BriefingPeriod.morning.requestID, BriefingPeriod.evening.requestID])

        if settings.morningEnabled {
            await schedule(.morning, hour: settings.morningHour, minute: settings.morningMinute)
        }
        if settings.eveningEnabled {
            await schedule(.evening, hour: settings.eveningHour, minute: settings.eveningMinute)
        }
    }

    private func schedule(_ period: BriefingPeriod, hour: Int, minute: Int) async {
        let content = await buildBriefing(period)
        var comps = DateComponents(); comps.hour = hour; comps.minute = minute
        let trigger = UNCalendarNotificationTrigger(dateMatching: comps, repeats: true)
        let req = UNNotificationRequest(identifier: period.requestID, content: content, trigger: trigger)
        try? await center.add(req)
    }

    /// Build the "Jarvis" briefing: greeting + weather/rain + top stories to watch.
    private func buildBriefing(_ period: BriefingPeriod) async -> UNMutableNotificationContent {
        let content = UNMutableNotificationContent()
        content.title = "\(period.greeting) \(period.emoji)"
        content.sound = .default

        var lines: [String] = []

        if settings.weatherEnabled, let lat = settings.latitude, let lon = settings.longitude,
           let w = await WeatherService.forecast(latitude: lat, longitude: lon,
                                                 place: settings.resolvedPlace ?? settings.locationName) {
            lines.append(w.summary)
        }

        let top = await topStories(limit: 3)
        if !top.isEmpty {
            lines.append("📣 Needs your attention:")
            for s in top { lines.append("• \(s.headline) (\(s.signalScore))") }
        } else if lines.isEmpty {
            lines.append("No new high-signal stories right now.")
        }

        content.body = lines.joined(separator: "\n")
        if let first = top.first {
            content.subtitle = "Top signal · \(Topic.label(first.topic))"
        }
        return content
    }

    private func topStories(limit: Int) async -> [StorySummary] {
        guard let page = try? await api.fetchStories(limit: 10) else { return [] }
        return Array(page.data.sorted { $0.signalScore > $1.signalScore }.prefix(limit))
    }

    /// Fire a one-off briefing shortly (used by the "Send a test briefing" button).
    func sendTestBriefing() async {
        guard isAuthorized else { return }
        let content = await buildBriefing(.morning)
        let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 3, repeats: false)
        try? await center.add(UNNotificationRequest(identifier: "briefing.test.\(UUID().uuidString)",
                                                    content: content, trigger: trigger))
    }

    // MARK: - Breaking alerts

    private func subscribeToBreakingEvents() {
        WebSocketManager.shared.events
            .receive(on: DispatchQueue.main)
            .sink { [weak self] event in self?.handle(event) }
            .store(in: &cancellables)
    }

    private func handle(_ event: WSEvent) {
        guard settings.enabled, settings.breakingEnabled, isAuthorized,
              event.type == .storyCreated,
              let score = event.signalScore, score >= settings.breakingMinSignal,
              let headline = event.headline else { return }
        notifyBreaking(headline: headline, topic: event.topic, score: score)
    }

    func notifyBreaking(headline: String, topic: String?, score: Int) {
        let content = UNMutableNotificationContent()
        content.title = "🔴 Breaking" + (topic.map { " · \(Topic.label($0))" } ?? "")
        content.body = "\(headline) (signal \(score))"
        content.sound = .default
        let req = UNNotificationRequest(identifier: "breaking.\(UUID().uuidString)",
                                        content: content, trigger: nil)
        center.add(req)
    }

    // MARK: - Background refresh

    func scheduleBackgroundRefresh() {
        let request = BGAppRefreshTaskRequest(identifier: jarvisBriefingRefreshID)
        request.earliestBeginDate = Date(timeIntervalSinceNow: 2 * 3600)
        try? BGTaskScheduler.shared.submit(request)
    }
}

// MARK: - Foreground presentation

extension NotificationManager: UNUserNotificationCenterDelegate {
    nonisolated func userNotificationCenter(_ center: UNUserNotificationCenter,
                                            willPresent notification: UNNotification) async
        -> UNNotificationPresentationOptions {
        [.banner, .sound, .list]
    }
}