/*

See LICENSE folder for this sample’s licensing information.

Abstract:

An example demonstrating adding accessibility to an NSView subclass that behaves like a button by implementing the NSAccessibilityButton protocol.

*/

import Cocoa

/*

 IMPORTANT: This is not a template for developing a custom control.

 This sample is intended to demonstrate how to add accessibility to

 existing custom controls that are not implemented using the preferred methods.

 For information on how to create custom controls please visit http://developer.apple.com

*/

// Note that CustomButtonView is an NSView subclass and needs to adopt "NSAccessibilityButton" or in this case implement the required functions.

/// - Tag: customButtonDeclare

class CustomButtonView: NSView {

    // MARK: - Internals

    private var pressed = false

    private var highlighted = false

    private var depressed = false

    var actionHandler: (() -> Void)?

    // Set to allow keyDown to be called.

    override var acceptsFirstResponder: Bool { return true }

    // MARK: - View Lifecycle

    required override init(frame frameRect: NSRect) {

        super.init(frame: frameRect)

        commonInit()

    }

    required init?(coder aDecoder: NSCoder) {

        super.init(coder: aDecoder)

        commonInit()

    }

    fileprivate func commonInit() {

        // Track the mouse for enter and exit for proper highlighting.

        let trackingArea = NSTrackingArea(rect: bounds,

                                          options: [NSTrackingArea.Options.activeAlways, NSTrackingArea.Options.mouseEnteredAndExited],

                                          owner: self,

                                          userInfo: nil)

        addTrackingArea(trackingArea)

    }

    // MARK: - Actions

    fileprivate func pressDown() {

        pressed = true

        depressed = true

        needsDisplay = true

    }

    fileprivate func pressUpInside(inside: Bool, highlight: Bool) {

        pressed = false

        depressed = false

        highlighted = highlight ? inside : false

        needsDisplay = true

        if inside {

            // Call our action handler (ultimately winding up in the view controller).

            if let actionHandler = actionHandler {

                actionHandler()

            }

        }

    }

    fileprivate func performAfterDelay(delay: Double, onCompletion: @escaping() -> Void) {

        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + delay, execute: {

            onCompletion()

        })

    }

    fileprivate func performPress () {

        // Set down and release after momentary delay so the button flickers.

        pressDown()

        let delayInSeconds = 0.1

        performAfterDelay(delay: delayInSeconds) {

            self.pressUpInside(inside: true, highlight: false)

        }

    }

    // MARK: - Drawing

    override func drawFocusRingMask() {

        bounds.fill()

    }

    override var focusRingMaskBounds: NSRect {

        return bounds

    }

    override func draw(_ dirtyRect: NSRect) {

        let upImage = NSImage(named: NSImage.Name(rawValue: ButtonImages.buttonUp))

        let downImage = NSImage(named: NSImage.Name(rawValue: ButtonImages.buttonDown))

        let highlightImage = NSImage(named: NSImage.Name(rawValue: ButtonImages.buttonHighlight))

        var imageToDraw = upImage

        if depressed {

            imageToDraw = downImage

        } else if highlighted {

            imageToDraw = highlightImage

        }

        imageToDraw?.draw(in: bounds, from: NSRect.zero, operation: NSCompositingOperation.sourceOver, fraction: 1.0)

    }

    // MARK: - Mouse events

    override func mouseDown(with event: NSEvent) {

        super.mouseDown(with: event)

        pressDown()

    }

    override func mouseUp(with event: NSEvent) {

        super.mouseUp(with: event)

        let localPoint = convert(event.locationInWindow, from:nil)

        let isInside = bounds.contains(localPoint)

        pressUpInside(inside: isInside, highlight: true)

    }

    override func mouseEntered(with event: NSEvent) {

        super.mouseEntered(with: event)

        highlighted = true

        depressed = pressed // Restore pressed state, possibly set before mouseExited.

        needsDisplay = true

    }

    override func mouseExited(with event: NSEvent) {

        super.mouseExited(with: event)

        highlighted = pressed

        depressed = false

        needsDisplay = true

    }

    // MARK: - Keyboard Events

    override func keyDown(with event: NSEvent) {

        guard let charactersIgnoringModifiers = event.charactersIgnoringModifiers, charactersIgnoringModifiers.characters.count == 1,

              let char = charactersIgnoringModifiers.characters.first

            else {

                super.keyDown(with: event)

                return

            }

        if char == " " {

            performPress()

        }

    }

}

// MARK: - Accessibility

extension CustomButtonView {

    override func accessibilityLabel() -> String? {

        return NSLocalizedString("Play", comment: "accessibility label of the Play button")

    }

    override func accessibilityHelp() -> String {

        return NSLocalizedString("Increase press count.", comment: "accessibility help of the Play button")

    }

    override func accessibilityPerformPress() -> Bool {

        // User did control-option-space keyboard shortcut.

        performPress()

        return true

    }

    /// - Tag: customButtonAdoption

    override func accessibilityRole() -> NSAccessibilityRole? {

        return NSAccessibilityRole.button

    }

    override func isAccessibilityElement() -> Bool {

        return true

    }

}