#if os(macOS)
import AppKit
import SwiftUI

struct DocsCloseGuard: NSViewRepresentable {
    let hasUnsaved: @MainActor () -> Bool
    let save: @MainActor () async -> Bool
    let discard: @MainActor () async -> Void
    func makeNSView(context: Context) -> DocsCloseGuardView {
        let view = DocsCloseGuardView()
        view.hasUnsaved = hasUnsaved; view.save = save; view.discard = discard
        return view
    }
    func updateNSView(_ view: DocsCloseGuardView, context: Context) {
        view.hasUnsaved = hasUnsaved; view.save = save; view.discard = discard
    }
}

@MainActor final class DocsCloseGuardView: NSView, NSWindowDelegate {
    var hasUnsaved: @MainActor () -> Bool = { false }
    var save: @MainActor () async -> Bool = { true }
    var discard: @MainActor () async -> Void = {}
    var presenting = false
    nonisolated(unsafe) weak var previousDelegate: (any NSWindowDelegate)?
    override func viewDidMoveToWindow() {
        super.viewDidMoveToWindow()
        guard let window, window.delegate !== self else { return }
        DocsCloseRegistry.views.removeAll { $0.value == nil }
        if !DocsCloseRegistry.views.contains(where: { $0.value === self }) {
            DocsCloseRegistry.views.append(WeakDocsCloseGuard(value: self))
        }
        previousDelegate = window.delegate
        window.delegate = self
    }
    override func responds(to selector: Selector!) -> Bool {
        super.responds(to: selector) || previousDelegate?.responds(to: selector) == true
    }
    override func forwardingTarget(for selector: Selector!) -> Any? { previousDelegate }
    func windowShouldClose(_ sender: NSWindow) -> Bool {
        guard hasUnsaved() else { return previousDelegate?.windowShouldClose?(sender) ?? true }
        guard !presenting else { return false }
        presenting = true
        let alert = Self.alert()
        alert.beginSheetModal(for: sender) { [weak self] response in
            guard let self else { return }
            Task { @MainActor in
                defer { self.presenting = false }
                if response == .alertFirstButtonReturn, await self.save() { sender.performClose(nil) }
                if response == .alertThirdButtonReturn { await self.discard(); sender.performClose(nil) }
            }
        }
        return false
    }
    static func alert() -> NSAlert {
        let alert = NSAlert()
        alert.messageText = String(localized: "native.close.pending.title", bundle: DocsResources.bundle)
        alert.informativeText = String(localized: "native.close.pending.detail", bundle: DocsResources.bundle)
        alert.addButton(withTitle: String(localized: "native.close.pending.save", bundle: DocsResources.bundle))
        alert.addButton(withTitle: String(localized: "native.close.pending.cancel", bundle: DocsResources.bundle))
        alert.addButton(withTitle: String(localized: "native.discard.action", bundle: DocsResources.bundle))
        return alert
    }
}
@MainActor private struct WeakDocsCloseGuard { weak var value: DocsCloseGuardView? }
@MainActor private enum DocsCloseRegistry { static var views: [WeakDocsCloseGuard] = [] }

@MainActor public final class DocsApplicationDelegate: NSObject, NSApplicationDelegate {
    public func applicationShouldTerminate(_ sender: NSApplication) -> NSApplication.TerminateReply {
        let views = DocsCloseRegistry.views.compactMap(\.value).filter { $0.window != nil }
        if views.contains(where: \.presenting) { return .terminateCancel }
        let pending = views.filter { $0.hasUnsaved() }
        guard !pending.isEmpty else { return .terminateNow }
        let response = DocsCloseGuardView.alert().runModal()
        guard response == .alertFirstButtonReturn || response == .alertThirdButtonReturn else { return .terminateCancel }
        Task { @MainActor in
            var saved = true
            for view in pending {
                if response == .alertThirdButtonReturn { await view.discard() }
                else if !(await view.save()) { saved = false }
            }
            sender.reply(toApplicationShouldTerminate: saved && !views.contains { $0.hasUnsaved() })
        }
        return .terminateLater
    }
}
#endif