import SwiftUI

/// The scene graph (02-architecture.md § Windows, § Launch and window lifecycle).
///
/// ### Four scenes, and why each is the kind it is
///
/// - **Welcome** is a `Window`: there is one of it, ever, and `openWindow(id:)` focuses the existing
///   one rather than making a second.
/// - **The restore bootstrap** is a `Window` too, and a deliberate oddity — see
///   `RestoreBootstrapView` for why launch-time work has to wear a window at all.
/// - **Boards** and **cards** are `WindowGroup(for:)`s, because their identity is a *value*: opening
///   with a ref that already has a window focuses it, which is how "one board window per root" and
///   "at most one card window per card (reopen focuses)" are enforced by the scene rather than by
///   bookkeeping.
///
/// ### Restoration is the registry's, not the system's
///
/// Both groups declare `.restorationBehavior(.disabled)`. The app already knows which boards were
/// open — the registry's open-now flags, which survive a crash and reopen in `lastOpened` order —
/// and letting AppKit *also* restore windows would produce duplicates, and worse, card windows
/// restored behind boards that never opened. One mechanism, and it is the one that can explain
/// itself when a board has moved or gone.
///
/// ### Which window appears at launch
///
/// Exactly one of welcome and the bootstrap, decided once in `init` and never re-derived: the
/// preference is read before any scene exists, and `restorables()` costs a bookmark resolution per
/// known board — a computed property here would pay that on every scene-graph evaluation.
@main
struct KanbanApp: App {

    @NSApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate

    @State private var appModel: AppModel

    /// Whether this launch restores boards: the preference is on **and** there is something flagged
    /// to restore. Welcome "appears only when nothing restores".
    private let shouldRestoreAtLaunch: Bool

    init() {
        let model = AppModel()
        _appModel = State(initialValue: model)
        shouldRestoreAtLaunch = AppPreferences.restoreOpenBoardsAtLaunch
            && !model.boardRegistry.restorables().isEmpty
        // The delegate is constructed by the adaptor before this runs, so this is the one place the
        // app's model and its AppKit half meet.
        appDelegate.appModel = model
    }

    var body: some Scene {
        Window("Welcome to Lanework", id: WindowID.welcome) {
            WelcomeView()
                .environment(appModel)
                .captureWindowActions(into: appModel)
        }
        .defaultLaunchBehavior(shouldRestoreAtLaunch ? .suppressed : .automatic)
        .restorationBehavior(.disabled)
        .windowResizability(.contentSize)
        // Its automatic Window-menu item is replaced by the explicit command below, so the title is
        // the one 11-command-nexus.md names rather than whatever the scene happens to be called.
        .commandsRemoved()

        Window("", id: WindowID.restoreBootstrap) {
            RestoreBootstrapView()
                .environment(appModel)
                .captureWindowActions(into: appModel)
        }
        .defaultLaunchBehavior(shouldRestoreAtLaunch ? .presented : .suppressed)
        .restorationBehavior(.disabled)
        .windowStyle(.plain)
        .defaultSize(width: 1, height: 1)
        .commandsRemoved()

        WindowGroup(id: WindowID.board, for: BoardWindowRef.self) { $ref in
            if let ref {
                BoardWindowHost(ref: ref)
                    .environment(appModel)
                    .captureWindowActions(into: appModel)
            }
        }
        .restorationBehavior(.disabled)
        .defaultLaunchBehavior(.suppressed)
        .commands { menuCommands }

        WindowGroup(id: WindowID.card, for: CardWindowRef.self) { $ref in
            if let ref {
                CardWindowHost(ref: ref)
                    .environment(appModel)
                    .captureWindowActions(into: appModel)
            }
        }
        .restorationBehavior(.disabled)
        .defaultLaunchBehavior(.suppressed)

        Settings {
            SettingsView()
                .environment(appModel)
                .captureWindowActions(into: appModel)
        }
    }

    /// The two menu items this milestone owns.
    ///
    /// **The titles are API** (04-interactions.md ▸ Configurable bindings): macOS's App Shortcuts
    /// mechanism remaps menu items *by title*, so these strings are the keys a user's custom binding
    /// is stored under. They are spelled exactly as 11-command-nexus.md inventories them, and
    /// changing one silently breaks every remap of it.
    @CommandsBuilder
    private var menuCommands: some Commands {
        CommandGroup(after: .newItem) {
            Button("Open…") {
                appModel.presentOpenPanel()
            }
            .keyboardShortcut("o", modifiers: .command)
        }

        CommandGroup(after: .windowList) {
            // No default chord — "— (no default)" in the Nexus is deliberate, not a gap; it remaps
            // like any other item.
            Button("Welcome to Lanework") {
                appModel.showWelcome()
            }
        }
    }
}