import Cocoa

final class AppDelegate: NSObject, NSApplicationDelegate, NSMenuDelegate {

    private var statusItem: NSStatusItem!
    private let menu = NSMenu()

    private struct Physical {
        let name: String
        let pixelWidth: Int
        let pixelHeight: Int
        let refreshRate: Int
    }

    private var lastPhysical: Physical?

    // lifecycle

    func applicationDidFinishLaunching(_ notification: Notification) {
        statusItem = NSStatusBar.system.statusItem(withLength: NSStatusItem.variableLength)
        if let button = statusItem.button {
            if let img = NSImage(systemSymbolName: "rectangle.on.rectangle",
                                 accessibilityDescription: "VirtualDisplay") {
                img.isTemplate = true
                button.image = img
            } else {
                button.title = "VD"
            }
        }
        menu.delegate = self
        menu.autoenablesItems = false
        statusItem.menu = menu

        ProcessInfo.processInfo.disableAutomaticTermination("VirtualDisplay running")
    }

    func applicationWillTerminate(_ notification: Notification) {
        DisplayManager.shared.disable()
    }

    // NSMenuDelegate

    func menuNeedsUpdate(_ menu: NSMenu) {
        guard menu === self.menu else { return }
        rebuild()
    }

    private func rebuild() {
        menu.removeAllItems()

        guard let phys = physicalDisplay() else {
            addDisabled("No display detected")
            menu.addItem(.separator())
            addQuit()
            return
        }

        addDisabled("\(phys.name)  (\(phys.pixelWidth)×\(phys.pixelHeight) @ \(phys.refreshRate)Hz)")
        menu.addItem(.separator())

        let activeScale = DisplayManager.shared.currentScale
        for s in availableScales(physicalPixelWidth: phys.pixelWidth,
                                 physicalPixelHeight: phys.pixelHeight) {
            let item = NSMenuItem(title: "\(s)%",
                                  action: #selector(chooseScale(_:)),
                                  keyEquivalent: "")
            item.target = self
            item.tag    = s
            item.state  = (activeScale == s) ? .on : .off
            menu.addItem(item)
        }

        if activeScale != nil {
            menu.addItem(.separator())
            addAction("Open Display Settings…", #selector(openDisplaySettings(_:)))
            menu.addItem(.separator())
            addAction("Disable", #selector(disable(_:)))
        }

        menu.addItem(.separator())
        addQuit()
    }

    // Menu helpers

    private func addDisabled(_ title: String) {
        let item = NSMenuItem(title: title, action: nil, keyEquivalent: "")
        item.isEnabled = false
        menu.addItem(item)
    }

    private func addAction(_ title: String, _ action: Selector) {
        let item = NSMenuItem(title: title, action: action, keyEquivalent: "")
        item.target = self
        menu.addItem(item)
    }

    private func addQuit() {
        menu.addItem(NSMenuItem(title: "Quit",
                                action: #selector(NSApplication.terminate(_:)),
                                keyEquivalent: "q"))
    }

    // Physical display detection

    private func physicalDisplay() -> Physical? {
        if let live = liveLookup() { lastPhysical = live }
        return lastPhysical
    }

    private func liveLookup() -> Physical? {
        let ourID = DisplayManager.shared.virtualDisplayID

        var count: UInt32 = 0
        guard CGGetActiveDisplayList(0, nil, &count) == .success, count > 0 else {
            return nil
        }
        var ids = [CGDirectDisplayID](repeating: 0, count: Int(count))
        guard CGGetActiveDisplayList(count, &ids, &count) == .success,
              let id = ids.first(where: { $0 != ourID }),
              let mode = CGDisplayCopyDisplayMode(id) else {
            return nil
        }

        let key = NSDeviceDescriptionKey("NSScreenNumber")
        let name = NSScreen.screens.first {
            ($0.deviceDescription[key] as? NSNumber)?.uint32Value == id
        }?.localizedName ?? lastPhysical?.name ?? "Display"
        let hz = mode.refreshRate > 0 ? Int(mode.refreshRate.rounded()) : 60

        return Physical(
            name: name,
            pixelWidth: mode.pixelWidth,
            pixelHeight: mode.pixelHeight,
            refreshRate: hz
        )
    }

    // Actions

    @objc private func chooseScale(_ sender: NSMenuItem) {
        guard let phys = physicalDisplay() else { return }
        let cfg = vdConfig(physicalPixelWidth: phys.pixelWidth,
                           physicalPixelHeight: phys.pixelHeight,
                           refreshRate: phys.refreshRate,
                           scalePercent: sender.tag)
        DisplayManager.shared.setScale(sender.tag, config: cfg)
    }

    @objc private func openDisplaySettings(_ sender: NSMenuItem) {
        let urls = [
            "x-apple.systempreferences:com.apple.Displays-Settings.extension",
            "x-apple.systempreferences:com.apple.preference.displays",
        ]
        for str in urls {
            if let url = URL(string: str), NSWorkspace.shared.open(url) {
                return
            }
        }
    }

    @objc private func disable(_ sender: NSMenuItem) {
        DisplayManager.shared.disable()
    }
}