import Foundation
import IndieBackup
import SwiftUI

/// IndieBackup's app-specific wiring (indie-backup skill): what gets backed up, and how the
/// app's in-memory board list is rebuilt after a restore.
///
/// **Why this type is constructed rather than defaulted.** `BackupConfiguration.backupRoot` is a
/// non-optional `URL`, but the ubiquity container resolves asynchronously and can fail outright
/// (`CloudHomeResolver`, CloudHome.swift) — there is no root to hand IndieBackup until
/// `BoardIndexStore.home` exists. Rather than answer with a placeholder path, this type is only
/// ever constructed once a real `CloudHome` is in hand (`MobileApp`'s `.task(id:)`); before that
/// there is no `BackupController` at all, and `SettingsTabView` renders a quiet disabled
/// explanation instead of a section built on a fabricated root.
final class MobileBackupConfiguration: BackupConfiguration {
    /// No dot. Shared by the Info.plist document-type/UTI registration
    /// (`dev.rzen.indie.kanban-backup`) and the archive filenames IndieBackup writes.
    static let fileExtension = "kanbanbackup"

    private let root: URL
    private let index: BoardIndexStore

    /// - Parameters:
    ///   - root: The resolved `CloudHome.documentsURL` — the same `Documents/` folder every
    ///     `.kanban` board lives directly inside. IndieBackup walks it file-by-file (it has no
    ///     notion of "package"), so a board's directory structure round-trips through a backup
    ///     as an ordinary tree of files — no directory registration or special-casing needed.
    ///   - index: Rescanned after a restore replaces the tree, in `rebuildCacheAfterRestore`.
    init(root: URL, index: BoardIndexStore) {
        self.root = root
        self.index = index
    }

    var backupFileExtension: String { Self.fileExtension }
    var backupDisplayName: String { "Lanework Backup" }
    var backupRoot: URL { root }

    /// `BoardIndexStore` caches nothing durable — no Core Data, no SwiftData, no file on disk —
    /// only an in-memory `[BoardSummary]` scanned straight from the files under `backupRoot`. A
    /// restore already replaced that tree by the time this runs, so the only rebuild step is
    /// asking the store to rescan it; a `BoardSession` for a board that's open elsewhere reloads
    /// its own content from disk independently the next time it's asked (BoardIndexStore's doc
    /// comment on the observer flow).
    ///
    /// `refresh()` only *starts* the rescan (it hands off to a detached `Task` and returns), so
    /// this reports done as soon as the request lands, not once the boards tab has repainted —
    /// same as any other call to `refresh()` in this app (e.g. pull-to-refresh).
    func rebuildCacheAfterRestore(progress: @escaping (Double, String) -> Void) async throws {
        progress(0, "Rescanning boards…")
        await index.refresh()
        progress(1, "Rescanning boards…")
    }
}

/// Threads the lazily-constructed `BackupController` from `MobileApp` down to `SettingsTabView`
/// (the backup section) and back up to `MobileApp`'s own `onOpenURL` handler (imported backup
/// files), without forcing `RootTabView` — or anything else between them — to know backup exists.
/// `nil` until the cloud home resolves; see `MobileBackupConfiguration`.
private struct BackupControllerKey: EnvironmentKey {
    static let defaultValue: BackupController? = nil
}

extension EnvironmentValues {
    var backupController: BackupController? {
        get { self[BackupControllerKey.self] }
        set { self[BackupControllerKey.self] = newValue }
    }
}