//
//  ViewController.swift
//  External Display
//
//  Created by Thomas Carroll on 9/20/21.
//

import Cocoa

let observatory = NotificationCenter.default

class ViewController: NSViewController {

    var connectedDisplay: NSScreen?
    var connectedDisplayWindow: NSWindow?
    var connectedDisplayView: NSView?
    var connectedDisplayCount: Int = 0
    var connectedDisplayID: UInt32 = 0
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        setupObservatory()
        if NSScreen.screens.count > 1 {
            handleDisplayConnectionChange(notification: nil)
        }
    }

    override var representedObject: Any? {
        didSet {
        // Update the view, if already loaded.
        }
    }
    
    override func viewWillDisappear() {
        connectedDisplayWindow?.close()
    }
    
    func setupObservatory() {
        observatory.addObserver(self, selector: #selector(handleDisplayConnectionChange), name: NSApplication.didChangeScreenParametersNotification, object: nil)
        observatory.addObserver(forName: .setupConnectedDisplayWindow, object: nil, queue: nil, using: setupConnectedDisplayWindow)
    }
    
    @objc func handleDisplayConnectionChange(notification: Notification?) {
        if connectedDisplayCount != NSScreen.screens.count {
            if connectedDisplayCount < NSScreen.screens.count {
                print("There is a connected display.")
                connectedDisplayCount = NSScreen.screens.count
                if let _ = NSScreen.screens.last {
                    if connectedDisplay != NSScreen.screens.last {
                        connectedDisplayID = NSScreen.screens.last!.displayID!
                        connectedDisplay = NSScreen.screens.last!
                    }
                } else {
                    connectedDisplayID = 0
                }
                if connectedDisplayID != 0 && !connectedDisplayIsActive {
                    observatory.post(name: .setupConnectedDisplayWindow, object: nil)
                }
            } else if connectedDisplayCount > NSScreen.screens.count {
                print("A connected display was removed.")
                connectedDisplayCount = NSScreen.screens.count
                connectedDisplayIsActive = false
                connectedDisplayWindow?.close()
                //connectedDisplayView = nil <- causes error @main in AppDelegate
                //connectedDisplayWindow = nil <- causes error @main in AppDelegate
                connectedDisplay = nil
                connectedDisplayID = 0
            }
        }
    }
    
    func setupConnectedDisplayWindow(notification: Notification) {
        if NSScreen.screens.count > 1 && !connectedDisplayIsActive {
            connectedDisplay = NSScreen.screens.last
            let mask: NSWindow.StyleMask = [.titled, .closable, .miniaturizable, .resizable]
            connectedDisplayWindow = NSWindow(contentRect: connectedDisplay!.frame, styleMask: mask, backing: .buffered, defer: true, screen: connectedDisplay) // <- causes error on subsequent connection
            connectedDisplayWindow?.level = .normal
            connectedDisplayWindow?.isOpaque = false
            connectedDisplayWindow?.backgroundColor = .clear
            connectedDisplayWindow?.hidesOnDeactivate = false
            let viewRect = NSRect(x: 0, y: 0, width: connectedDisplay!.frame.width, height: connectedDisplay!.frame.height)
            connectedDisplayView = ConnectedDisplayView(frame: viewRect)
            connectedDisplayWindow?.contentView = connectedDisplayView
            connectedDisplayWindow?.orderFront(nil)
            connectedDisplayView?.window?.toggleFullScreen(self)
            connectedDisplayIsActive = true
            observatory.post(name: .setupConnectedDisplayView, object: nil)
        }
    }
}

extension Notification.Name {
    static var setupConnectedDisplayWindow: Notification.Name {
        return .init(rawValue: "ViewController.setupConnectedDisplayView")
    }
    static var setupConnectedDisplayView: Notification.Name {
        return .init(rawValue: "ConnectedDisplayView.setupConnectedDisplayView")
    }
}

extension NSScreen {
    var displayID: CGDirectDisplayID? {
        return deviceDescription[NSDeviceDescriptionKey(rawValue: "NSScreenNumber")] as? CGDirectDisplayID
    }
}