import SwiftUI
import AppKit

extension Notification.Name {
    static let promptPanelDidShow = Notification.Name("PromptPanelDidShowNotification")
}

private final class KeyablePanel: NSPanel {
    override var canBecomeKey: Bool { true }
    override var canBecomeMain: Bool { false }
}

@MainActor
final class PanelController: NSObject {
    static let shared = PanelController()

    private var panel: KeyablePanel?
    private var pasteMonitor: Any?

    var isVisible: Bool { panel?.isVisible ?? false }

    func toggle() {
        isVisible ? hide() : show()
    }

    func show() {
        let panel = panel ?? makePanel()
        if UserDefaults.standard.string(forKey: "NSWindow Frame PromptPanel") == nil {
            positionAtRightEdge(panel)
        }
        NSApp.activate(ignoringOtherApps: true)
        panel.makeKeyAndOrderFront(nil)
        NSLog("Prompt: panel shown")
        NotificationCenter.default.post(name: .promptPanelDidShow, object: nil)
    }

    func hide() {
        panel?.orderOut(nil)
        NSApp.deactivate()
        NSLog("Prompt: panel hidden (app keeps running for the Shift-Shift hotkeys)")
    }

    private func makePanel() -> KeyablePanel {
        let panel = KeyablePanel(
            contentRect: NSRect(x: 0, y: 0, width: 360, height: 640),
            styleMask: [.titled, .closable, .resizable, .nonactivatingPanel, .fullSizeContentView],
            backing: .buffered,
            defer: false
        )
        panel.titleVisibility = .hidden
        panel.titlebarAppearsTransparent = true
        panel.standardWindowButton(.miniaturizeButton)?.isHidden = true
        panel.standardWindowButton(.zoomButton)?.isHidden = true
        panel.level = .floating
        panel.isMovableByWindowBackground = true
        panel.hidesOnDeactivate = false
        panel.isReleasedWhenClosed = false
        panel.isOpaque = true
        // Match the SwiftUI content so the titlebar strip and any resize flash
        // do not show the system grey through.
        panel.backgroundColor = Theme.background
        panel.collectionBehavior = [.canJoinAllSpaces, .fullScreenAuxiliary]
        panel.contentView = NSHostingView(rootView: PanelView(store: Store.shared))
        panel.setFrameAutosaveName("PromptPanel")
        self.panel = panel
        installPasteMonitor()
        return panel
    }

    private func positionAtRightEdge(_ panel: NSPanel) {
        guard let screen = NSScreen.main?.visibleFrame else { return }
        let size = NSSize(width: 360, height: screen.height - 24)
        panel.setContentSize(size)
        panel.setFrameOrigin(NSPoint(x: screen.maxX - size.width - 12, y: screen.minY + 12))
    }

    // Cmd+V is handled here rather than left to a menu key equivalent. The
    // panel is a nonactivating panel, so it can be key while the app is not
    // active, and menu key equivalents are not reliably delivered in that
    // state — which is what silently broke pasting. Dispatching paste: to the
    // responder chain ourselves removes that dependency.
    private func installPasteMonitor() {
        guard pasteMonitor == nil else { return }
        pasteMonitor = NSEvent.addLocalMonitorForEvents(matching: .keyDown) { [weak self] event in
            guard let self, let panel = self.panel, event.window == panel else { return event }
            let modifiers = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
            guard modifiers == [.command], event.charactersIgnoringModifiers == "v" else { return event }

            let pasteboard = NSPasteboard.general
            if pasteboard.string(forType: .string) != nil {
                NSApp.sendAction(#selector(NSText.paste(_:)), to: nil, from: nil)
                return nil
            }
            if let images = pasteboard.readObjects(forClasses: [NSImage.self], options: nil) as? [NSImage],
               let image = images.first {
                Task { @MainActor in Store.shared.addImage(image) }
                return nil
            }
            return event
        }
    }
}