import UserNotifications
import Foundation

/// Centralised local-notification sender.
///
/// Uses notification identifiers as categories — posting the same id replaces
/// any previous notification in that category, preventing stale banners from
/// stacking up.
enum NotificationService {
    static func notifyBackupStarted(count: Int) {
        guard count > 0 else { return }
        post(
            id: "kisani.backup.started",
            title: "Backup started",
            body: "Kisani is backing up \(count) new \(count == 1 ? "item" : "items")."
        )
    }

    static func notifyBackupCompleted(uploaded: Int, total: Int) {
        post(
            id: "kisani.backup.completed",
            title: "Backup complete",
            body: total > 0
                ? "All \(total) photos are safe."
                : "\(uploaded) \(uploaded == 1 ? "item" : "items") backed up."
        )
    }

    static func notifyBackupPaused(pendingCount: Int) {
        post(
            id: "kisani.backup.paused",
            title: "Backup paused",
            body: pendingCount > 0
                ? "Kisani will continue \(pendingCount) \(pendingCount == 1 ? "item" : "items") when your NAS is reachable."
                : "Kisani will continue when your NAS is reachable."
        )
    }

    static func notifyBackupFailed(count: Int) {
        post(
            id: "kisani.backup.failed",
            title: "Backup failed",
            body: "\(count) \(count == 1 ? "item" : "items") could not be backed up. Tap to review."
        )
    }

    static func notifyNASOffline() {
        post(
            id: "kisani.nas.offline",
            title: "NAS unreachable",
            body: "Kisani will resume backup when your NAS is back online."
        )
    }

    // MARK: — Private

    private static func post(id: String, title: String, body: String) {
        let content = UNMutableNotificationContent()
        content.title = title
        content.body  = body
        content.sound = .default
        let request = UNNotificationRequest(identifier: id, content: content, trigger: nil)
        UNUserNotificationCenter.current().add(request) { _ in }
    }
}