import Foundation
import Photos

@MainActor
final class BackupViewModel: ObservableObject {
    @Published var totalPhotoCount: Int = 0
    @Published var alreadySafeCount: Int = 0
    @Published var notBackedUpCount: Int = 0
    @Published var photosAuthStatus: PHAuthorizationStatus = PHPhotoLibrary.authorizationStatus(for: .readWrite)

    private let photoService = PhotoLibraryService()
    private var fetchedAssets: [PhotoAsset] = []

    func loadPhotoCount(filter: BackupFilter) {
        let assets = photoService.fetchAssets(filter: filter)
        fetchedAssets = assets
        totalPhotoCount = assets.count
        // Conservative initial state until NAS scan completes
        alreadySafeCount = 0
        notBackedUpCount = assets.count
    }

    // Called after NAS directory listing loads.
    // Matches by lowercased filename — same heuristic BackupEngine uses for skip checks.
    // This gives an accurate pre-scan "Already Safe / Not Backed Up" split before
    // the user ever taps Start Backup.
    func compareWithNAS(nasItems: [NASItem]) {
        let nasFilenames = Set(
            nasItems
                .filter { !$0.isDirectory }
                .map { $0.name.lowercased() }
        )
        var safe = 0
        for asset in fetchedAssets {
            if nasFilenames.contains(asset.filename.lowercased()) {
                safe += 1
            }
        }
        alreadySafeCount = safe
        notBackedUpCount = totalPhotoCount - safe
    }

    func requestPhotosAccess() async {
        photosAuthStatus = await photoService.requestAuthorization()
    }
}