// ── Timer Store ────────────────────────────────────────────────
// Observable store managing all timers — equivalent of Zustand store
// Persists to UserDefaults (SwiftData migration in future)

import Foundation
import Combine
import ActivityKit

@MainActor
final class TimerStore: ObservableObject {
    // MARK: - Published State

    @Published var timers: [CMTimer] = []
    @Published var now: Date = Date()

    // MARK: - Private

    private var tickTimer: Timer?
    private let persistenceKey = "chronomind-timers"
    private let notifications = CMNotificationManager.shared
    private let sharedData = SharedTimerDataManager.shared
    private let liveActivity = LiveActivityManager.shared
    private let syncManager = PlatformSyncManager.shared

    // MARK: - Init

    init() {
        loadTimers()
        startTicking()
        syncToSharedData()
    }

    deinit {
        tickTimer?.invalidate()
    }

    // MARK: - CRUD

    func addAlarm(_ params: CreateAlarmParams) -> CMTimer {
        let timer = createAlarm(params)
        timers.append(timer)
        notifications.scheduleNotifications(for: timer)
        saveTimers()
        liveActivity.startActivity(for: timer)
        syncManager.enqueueChange(timer, action: .create)
        return timer
    }

    func addCountdown(_ params: CreateCountdownParams) -> CMTimer {
        let timer = createCountdown(params)
        timers.append(timer)
        notifications.scheduleNotifications(for: timer)
        saveTimers()
        liveActivity.startActivity(for: timer)
        syncManager.enqueueChange(timer, action: .create)
        return timer
    }

    func addPomodoro(_ params: CreatePomodoroParams = CreatePomodoroParams()) -> CMTimer {
        let timer = createPomodoro(params)
        timers.append(timer)
        notifications.scheduleNotifications(for: timer)
        saveTimers()
        liveActivity.startActivity(for: timer)
        syncManager.enqueueChange(timer, action: .create)
        return timer
    }

    func removeTimer(_ id: String) {
        liveActivity.endActivity(for: id)
        timers.removeAll { $0.id == id }
        notifications.removeNotifications(for: id)
        saveTimers()
        syncManager.enqueueDelete(timerId: id)
    }

    // MARK: - State Transitions

    func pause(_ id: String) {
        updateTimer(id) { pauseTimer($0) }
        if let updated = getTimer(id) { syncManager.enqueueChange(updated, action: .update) }
    }

    func resume(_ id: String) {
        updateTimer(id) { t in
            let resumed = resumeTimer(t)
            self.notifications.scheduleNotifications(for: resumed)
            return resumed
        }
        if let updated = getTimer(id) { syncManager.enqueueChange(updated, action: .update) }
    }

    func fire(_ id: String) {
        updateTimer(id) { fireTimer($0) }
    }

    func snooze(_ id: String, minutes: Int) {
        updateTimer(id) { t in
            let snoozed = snoozeTimer(t, snoozeMinutes: minutes)
            self.notifications.scheduleNotifications(for: snoozed)
            return snoozed
        }
        if let updated = getTimer(id) { syncManager.enqueueChange(updated, action: .update) }
    }

    func dismiss(_ id: String) {
        liveActivity.endActivity(for: id)
        // Check for late dismissal before updating state
        if let timer = getTimer(id) {
            checkForRescheduleSuggestion(dismissedTimer: timer)
        }
        updateTimer(id) { dismissTimer($0) }
        if let updated = getTimer(id) { syncManager.enqueueChange(updated, action: .update) }
    }

    func complete(_ id: String) {
        liveActivity.endActivity(for: id)
        updateTimer(id) { completeTimer($0) }
        if let updated = getTimer(id) { syncManager.enqueueChange(updated, action: .update) }
        // Record completion for streak tracking
        GamificationStore.shared.recordCompletion()
    }

    func advancePom(_ id: String) {
        guard let index = timers.firstIndex(where: { $0.id == id }) else { return }
        if let next = advancePomodoro(timers[index]) {
            timers[index] = next
            notifications.scheduleNotifications(for: next)
            saveTimers()
            syncManager.enqueueChange(next, action: .update)
        }
    }

    // MARK: - Tick

    func tick() {
        let currentTime = Date()
        now = currentTime

        var changed = false

        for i in timers.indices {
            // Check if timer should fire
            if shouldTimerFire(timers[i], now: currentTime) {
                timers[i] = fireTimer(timers[i])
                changed = true
                // Haptic feedback
                HapticEngine.fire(urgency: timers[i].urgency)
                continue
            }

            // Check cascade warnings
            let newlyFired = checkWarnings(&timers[i].warnings, now: currentTime)
            if !newlyFired.isEmpty {
                changed = true
                // Update state to warning if still active
                if timers[i].state == .active {
                    timers[i].state = .warning
                }
                // Haptic feedback for warning
                HapticEngine.warning(urgency: timers[i].urgency)
            }
        }

        if changed {
            saveTimers()
        }

        // Update Live Activity for the next firing timer
        if let next = nextFiringTimer {
            liveActivity.updateActivity(for: next)
        }
    }

    // MARK: - Reschedule

    @Published var lastReschedule: RescheduleResult?
    @Published var rescheduleSuggestions: [RescheduleSuggestion] = []

    /// Apply a reschedule action
    func applyReschedule(_ action: RescheduleAction) {
        let result = RescheduleEngine.apply(action: action, to: timers)
        lastReschedule = result
        timers = result.updatedTimers

        // Reschedule notifications for affected timers
        for id in result.affectedTimerIds {
            if let timer = getTimer(id) {
                notifications.scheduleNotifications(for: timer)
            }
        }

        saveTimers()

        // Auto-clear undo after 1 hour
        DispatchQueue.main.asyncAfter(deadline: .now() + 3600) { [weak self] in
            if self?.lastReschedule?.timestamp == result.timestamp {
                self?.lastReschedule = nil
            }
        }
    }

    /// Undo the last reschedule
    func undoReschedule() {
        guard let result = lastReschedule else { return }
        timers = RescheduleEngine.undo(result: result, in: timers)

        // Reschedule notifications for restored timers
        for id in result.affectedTimerIds {
            if let timer = getTimer(id) {
                notifications.scheduleNotifications(for: timer)
            }
        }

        lastReschedule = nil
        saveTimers()
    }

    /// Check for late dismissal and generate suggestions
    func checkForRescheduleSuggestion(dismissedTimer: CMTimer) {
        let now = Date()
        if let delay = RescheduleEngine.detectLateDismissal(timer: dismissedTimer, dismissedAt: now) {
            rescheduleSuggestions = RescheduleSuggestion.suggestionsForLateDismissal(
                timer: dismissedTimer,
                dismissDelay: delay
            )
        }
    }

    /// Clear current suggestions
    func clearRescheduleSuggestions() {
        rescheduleSuggestions = []
    }

    // MARK: - Queries

    func getTimer(_ id: String) -> CMTimer? {
        timers.first { $0.id == id }
    }

    var activeTimers: [CMTimer] {
        timers.filter { [.active, .warning, .snoozed, .paused, .firing].contains($0.state) }
    }

    var nextFiringTimer: CMTimer? {
        timers
            .filter { [.active, .warning].contains($0.state) }
            .sorted { $0.targetTime < $1.targetTime }
            .first
    }

    // MARK: - Private Helpers

    private func updateTimer(_ id: String, updater: (CMTimer) -> CMTimer) {
        guard let index = timers.firstIndex(where: { $0.id == id }) else { return }
        timers[index] = updater(timers[index])
        saveTimers()
    }

    private func startTicking() {
        tickTimer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] _ in
            Task { @MainActor in
                self?.tick()
            }
        }
    }

    // MARK: - Persistence (UserDefaults for now, SwiftData later)

    private func saveTimers() {
        guard let data = try? JSONEncoder().encode(timers) else { return }
        UserDefaults.standard.set(data, forKey: persistenceKey)
        syncToSharedData()
    }

    private func loadTimers() {
        guard let data = UserDefaults.standard.data(forKey: persistenceKey),
              let saved = try? JSONDecoder().decode([CMTimer].self, from: data) else { return }
        timers = saved
    }

    // MARK: - App Group Sync

    /// Sync timer data to App Group for widgets and watchOS
    private func syncToSharedData() {
        sharedData.writeTimers(timers)
        sharedData.writeActiveTimer(nextFiringTimer)
        reloadWidgets()
    }

    /// Reload all WidgetKit timelines when data changes
    private func reloadWidgets() {
        // Post notification that widget-aware code can observe
        NotificationCenter.default.post(name: .chronoMindTimersDidChange, object: nil)
    }
}

// MARK: - Notification Names

extension Notification.Name {
    static let chronoMindTimersDidChange = Notification.Name("chronoMindTimersDidChange")
}