import SwiftUI
import os

/// The launch-time restoration pass, wearing a window because that is the only place SwiftUI lets
/// work like this run.
///
/// ### Why a window at all
///
/// Restoration has to open windows, and opening a window needs `openWindow`, which is only readable
/// from a view. An `App.init()` cannot do it and `AppDelegate` has no environment. So the app
/// presents one throwaway window at launch — 1×1, plain, ordered straight back out, absent from the
/// Window menu — whose only job is to run the pass and then dismiss itself. It exists for a few
/// hundred milliseconds and never draws.
///
/// It is presented **only** when there is something to open (`KanbanApp` decides, via
/// `LaunchPlan.presentsBootstrap`), so the ordinary launch-to-welcome path never creates it.
///
/// ### What the pass does
///
/// Reads the registry's flagged records in `lastOpened` order (`BoardRegistry.restorables()`), opens
/// the available ones, and records the unavailable ones as failures — 02 § Launch and window
/// lifecycle: "Other restorations proceed unaffected — never a launch-time modal chain, never a
/// silent drop." Welcome comes up only if nothing was even attempted; a board that *was* attempted
/// and then failed to load opens welcome from its own host, which is the same rule applied one layer
/// down and keeps this pass from having to wait on loads it did not perform.
///
/// ### And one other pass, for the same reason
///
/// The accessibility audit suite's fixture board (`UITestLaunch`) is built and opened here too. It is
/// the same job with a different source — filesystem work that must happen before the first real
/// window, needing `openWindow` to finish — and giving it a second throwaway window would be a second
/// copy of everything this file explains. Which pass runs is `plan`'s to say and nothing else's.
struct RestoreBootstrapView: View {

    /// Decided in `KanbanApp.init()`; this view only dispatches on it.
    let plan: LaunchPlan

    @Environment(AppModel.self) private var appModel
    @Environment(\.openWindow) private var openWindow
    @Environment(\.dismissWindow) private var dismissWindow

    @State private var windowController = HostedWindowController()

    private static let logger = Logger(subsystem: "dev.rzen.indie.Kanban", category: "launch")

    var body: some View {
        Color.clear
            .frame(width: 1, height: 1)
            .background(WindowAccessor(controller: windowController))
            .onAppear {
                // Out of sight before it can be seen. `orderOut` rather than a hidden style because
                // the scene must still exist — a window SwiftUI never presents never runs its task.
                windowController.onAttach = { window in
                    window.alphaValue = 0
                    window.orderOut(nil)
                }
                if let window = windowController.window {
                    windowController.onAttach?(window)
                }
            }
            .task { await restore() }
    }

    private func restore() async {
        // Captured directly rather than waiting for `CaptureOpenWindow`'s `onAppear`: this task is
        // the app's first act, and `openBoard` needs the action now.
        appModel.captureWindowActions(open: openWindow, dismiss: dismissWindow)

        switch plan {
        case .uiTestFixture:
            openFixtureBoard()
        case .restoreBoards, .welcome:
            // `.welcome` never presents this window, so it cannot arrive here — and if a future
            // launch path let it, the restoration pass is the harmless answer: it finds nothing
            // flagged and shows welcome, which is what `.welcome` asked for anyway.
            restoreFlaggedBoards()
        }

        dismissWindow(id: WindowID.restoreBootstrap)
    }

    private func restoreFlaggedBoards() {
        var attempted = 0
        for board in appModel.boardRegistry.restorables() {
            switch board {
            case let .available(_, url):
                appModel.openBoard(at: url)
                attempted += 1
            case let .unavailable(record):
                Self.logger.error("a flagged board could not be restored — its bookmark no longer resolves")
                appModel.recordLaunchFailure(
                    path: record.lastKnownPath,
                    message: "This board is unavailable. Its volume may be offline, or it may have been moved or deleted."
                )
            }
        }

        if attempted == 0 {
            appModel.showWelcome()
        }
    }

    /// The audit suite's board: built here, opened through the same `openBoard` every other path
    /// uses, so it registers, bookmarks and titles itself exactly like a board the user opened.
    ///
    /// **A failure lands on welcome as an ordinary launch failure**, with the fixture's own path on
    /// it. That is deliberate: a suite whose fixture failed to build would otherwise audit an empty
    /// screen and pass, which is the one outcome an accessibility gate must never produce.
    private func openFixtureBoard() {
        do {
            let url = try UITestLaunch.materializeFixtureBoard()
            appModel.openBoard(at: url)
        } catch {
            Self.logger.error("the UI-test fixture board could not be built: \(error.localizedDescription, privacy: .public)")
            appModel.recordLaunchFailure(
                path: UITestLaunch.fixtureBoardURL.path,
                message: "The UI-test fixture board could not be built: \(error.localizedDescription)"
            )
            appModel.showWelcome()
        }
    }
}