cards-native/Sources/Core/Sync/WidgetSnapshot.swift

import Foundation

/// Datei-Format für die WidgetKit-Extension. Wird vom Haupt-Target nach
/// jedem erfolgreichen `DeckListStore.refresh()` in den shared App-Group-
/// Container geschrieben; das Widget liest es im TimelineProvider.
///
/// Wire ist bewusst stabil + schmal — nur was das Widget rendert.
/// Neue Felder dürfen additiv dazukommen, alte Felder bleiben.
struct WidgetSnapshot: Codable, Sendable {
    let updatedAt: Date
    let totalDueCount: Int
    let topDecks: [Entry]

    struct Entry: Codable, Sendable, Identifiable {
        let id: String       // deck-id
        let name: String
        let dueCount: Int
        let colorHex: String?
    }
}

/// Liest und schreibt WidgetSnapshot in den shared App-Group-Container.
enum WidgetSnapshotStore {
    /// App-Group-ID — muss exakt mit dem Entitlement-Eintrag matchen.
    static let appGroupID = "group.ev.mana.cardecky"
    static let snapshotFilename = "widget-snapshot.json"

    static var snapshotURL: URL? {
        FileManager.default
            .containerURL(forSecurityApplicationGroupIdentifier: appGroupID)?
            .appendingPathComponent(snapshotFilename)
    }

    static func write(_ snapshot: WidgetSnapshot) {
        guard let url = snapshotURL else { return }
        let encoder = JSONEncoder()
        encoder.dateEncodingStrategy = .iso8601
        guard let data = try? encoder.encode(snapshot) else { return }
        try? data.write(to: url, options: .atomic)
    }

    static func read() -> WidgetSnapshot? {
        guard let url = snapshotURL, let data = try? Data(contentsOf: url) else { return nil }
        let decoder = JSONDecoder()
        decoder.dateDecodingStrategy = .iso8601
        return try? decoder.decode(WidgetSnapshot.self, from: data)
    }
}