import Foundation
import Combine
import AppKit

@MainActor
final class TimerStore: ObservableObject {
    @Published var timers: [TimerItem] = [] {
        didSet {
            save()
        }
    }

    private var ticker: AnyCancellable?
    private let storageKey = "multiTimerApp.timers.v2"

    init() {
        load()

        if timers.isEmpty {
            timers = (1...10).map {
                TimerItem(name: "Timer \($0)", durationSeconds: 10 * 60)
            }
        }

        // Beim Start prüfen: Falls Timer vor App-Ende lief, endDate verwenden.
        reconcileRunningTimers()

        ticker = Timer
            .publish(every: 0.5, on: .main, in: .common)
            .autoconnect()
            .sink { [weak self] _ in
                Task { @MainActor in
                    self?.tick()
                }
            }

        NotificationCenter.default.addObserver(
            forName: NSWorkspace.didWakeNotification,
            object: nil,
            queue: .main
        ) { [weak self] _ in
            Task { @MainActor in
                self?.tick()
            }
        }
    }

    func addTimer() {
        guard timers.count < 15 else { return }

        timers.append(
            TimerItem(
                name: "Timer \(timers.count + 1)",
                durationSeconds: 10 * 60
            )
        )
    }

    func removeTimer(_ timer: TimerItem) {
        AlarmWindowManager.shared.closeWindow(timerID: timer.id)
        timers.removeAll { $0.id == timer.id }
    }

    func start(_ timer: TimerItem) {
        guard let index = timers.firstIndex(where: { $0.id == timer.id }) else { return }

        if timers[index].remainingSeconds <= 0 {
            timers[index].remainingSeconds = timers[index].durationSeconds
        }

        timers[index].endDate = Date().addingTimeInterval(TimeInterval(timers[index].remainingSeconds))
        timers[index].isRunning = true
    }

    func pause(_ timer: TimerItem) {
        guard let index = timers.firstIndex(where: { $0.id == timer.id }) else { return }

        if let endDate = timers[index].endDate {
            timers[index].remainingSeconds = max(0, Int(ceil(endDate.timeIntervalSinceNow)))
        }

        timers[index].isRunning = false
        timers[index].endDate = nil
    }

    func reset(_ timer: TimerItem) {
        guard let index = timers.firstIndex(where: { $0.id == timer.id }) else { return }

        timers[index].isRunning = false
        timers[index].endDate = nil
        timers[index].remainingSeconds = timers[index].durationSeconds

        AlarmWindowManager.shared.closeWindow(timerID: timer.id)
    }

    func repeatTimer(timerID: UUID) {
        guard let index = timers.firstIndex(where: { $0.id == timerID }) else { return }

        timers[index].remainingSeconds = timers[index].durationSeconds
        timers[index].endDate = Date().addingTimeInterval(TimeInterval(timers[index].durationSeconds))
        timers[index].isRunning = true
    }

    func finishTimer(timerID: UUID) {
        guard let index = timers.firstIndex(where: { $0.id == timerID }) else { return }

        timers[index].isRunning = false
        timers[index].endDate = nil
        timers[index].remainingSeconds = timers[index].durationSeconds
    }

    func durationChanged(for timerID: UUID, newDurationSeconds: Int) {
        guard let index = timers.firstIndex(where: { $0.id == timerID }) else { return }

        let safeSeconds = max(60, min(24 * 3600, newDurationSeconds))
        timers[index].durationSeconds = safeSeconds

        if !timers[index].isRunning {
            timers[index].remainingSeconds = safeSeconds
            timers[index].endDate = nil
        }
    }

    private func tick() {
        var changed = false

        for index in timers.indices where timers[index].isRunning {
            guard let endDate = timers[index].endDate else {
                timers[index].endDate = Date().addingTimeInterval(TimeInterval(timers[index].remainingSeconds))
                changed = true
                continue
            }

            let secondsLeft = max(0, Int(ceil(endDate.timeIntervalSinceNow)))

            if timers[index].remainingSeconds != secondsLeft {
                timers[index].remainingSeconds = secondsLeft
                changed = true
            }

            if secondsLeft <= 0 {
                handleExpiredTimer(at: index)
                changed = true
            }
        }

        if changed {
            objectWillChange.send()
            save()
        }
    }

    private func handleExpiredTimer(at index: Int) {
        timers[index].remainingSeconds = 0
        timers[index].isRunning = false
        timers[index].endDate = nil
        timers[index].completedCount += 1

        AlarmManager.shared.playAlarm()

        let timerID = timers[index].id
        let timerName = timers[index].name

        if timers[index].autoRepeat {
            timers[index].remainingSeconds = timers[index].durationSeconds
            timers[index].endDate = Date().addingTimeInterval(TimeInterval(timers[index].durationSeconds))
            timers[index].isRunning = true
        } else {
            AlarmWindowManager.shared.showAlarm(
                timerID: timerID,
                timerName: timerName,
                onRepeat: { [weak self] in
                    self?.repeatTimer(timerID: timerID)
                },
                onFinish: { [weak self] in
                    self?.finishTimer(timerID: timerID)
                }
            )
        }
    }

    private func reconcileRunningTimers() {
        for index in timers.indices where timers[index].isRunning {
            if let endDate = timers[index].endDate {
                timers[index].remainingSeconds = max(0, Int(ceil(endDate.timeIntervalSinceNow)))
            } else {
                timers[index].endDate = Date().addingTimeInterval(TimeInterval(timers[index].remainingSeconds))
            }

            if timers[index].remainingSeconds <= 0 {
                timers[index].isRunning = false
                timers[index].remainingSeconds = 0
            }
        }
    }

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

    private func load() {
        guard
            let data = UserDefaults.standard.data(forKey: storageKey),
            let decoded = try? JSONDecoder().decode([TimerItem].self, from: data)
        else {
            return
        }

        timers = decoded
    }
}