import Foundation
import WidgetKit

/// Liest WidgetSnapshot aus dem shared App-Group-Container und schneidet
/// eine Timeline mit 30-Minuten-Refresh. Haupt-App ruft zusätzlich nach
/// jedem Refresh `WidgetCenter.shared.reloadAllTimelines()` auf, dann ist
/// das Update sofort sichtbar.
struct DueEntry: TimelineEntry, Sendable {
    let date: Date
    let totalDueCount: Int
    let topDecks: [WidgetSnapshot.Entry]
    let isPlaceholder: Bool

    static let placeholder = DueEntry(
        date: .now,
        totalDueCount: 0,
        topDecks: [],
        isPlaceholder: true
    )
}

struct DueProvider: TimelineProvider {
    func placeholder(in _: Context) -> DueEntry {
        .placeholder
    }

    func getSnapshot(in _: Context, completion: @escaping @Sendable (DueEntry) -> Void) {
        completion(loadEntry())
    }

    func getTimeline(in _: Context, completion: @escaping @Sendable (Timeline<DueEntry>) -> Void) {
        let entry = loadEntry()
        let next = Calendar.current.date(byAdding: .minute, value: 30, to: .now) ?? .now
        completion(Timeline(entries: [entry], policy: .after(next)))
    }

    private func loadEntry() -> DueEntry {
        guard let snapshot = WidgetSnapshotStore.read() else {
            return .placeholder
        }
        return DueEntry(
            date: snapshot.updatedAt,
            totalDueCount: snapshot.totalDueCount,
            topDecks: snapshot.topDecks,
            isPlaceholder: false
        )
    }
}