import Foundation
import UserNotifications

/// Schedules local repeating notifications for Gassi-Zeiten so reminders work
/// even when the app is offline. One UNCalendarNotificationTrigger per weekday.
@MainActor
enum GassiZeitenScheduler {
    static func reschedule(_ z: GassiZeit) async {
        cancel(forId: z.id)
        guard z.aktiv != 0 else { return }

        let parts = z.uhrzeit.split(separator: ":")
        guard parts.count == 2,
              let h = Int(parts[0]),
              let m = Int(parts[1])
        else { return }

        let content = UNMutableNotificationContent()
        content.title = "Gassi-Zeit"
        content.body = z.notiz?.isEmpty == false ? z.notiz! : "Zeit für deine Gassi-Runde."
        content.sound = .default

        let center = UNUserNotificationCenter.current()
        for wt in z.wochentage {
            let weekday = weekdayNumber(for: wt)
            guard weekday > 0 else { continue }
            var comps = DateComponents()
            comps.weekday = weekday
            comps.hour = h
            comps.minute = m
            let trigger = UNCalendarNotificationTrigger(dateMatching: comps, repeats: true)
            let request = UNNotificationRequest(
                identifier: "gz-\(z.id)-\(weekday)",
                content: content,
                trigger: trigger
            )
            try? await center.add(request)
        }
    }

    static func cancel(forId id: Int) {
        let ids = (1...7).map { "gz-\(id)-\($0)" }
        UNUserNotificationCenter.current().removePendingNotificationRequests(withIdentifiers: ids)
    }

    private static func weekdayNumber(for code: String) -> Int {
        switch code.lowercased() {
        case "so": return 1
        case "mo": return 2
        case "di": return 3
        case "mi": return 4
        case "do": return 5
        case "fr": return 6
        case "sa": return 7
        default:   return 0
        }
    }
}