/*

See LICENSE folder for this sample’s licensing information.

Abstract:

An example demonstrating adding accessibility to custom MTKView subclass that behaves

 like a stepper by implementing the NSAccessibilityStepper protocol.

*/

import Cocoa

import MetalKit

/*

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

 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

 */

class CustomStepperView: MTKView, NSAccessibilityStepper {

    // MARK: - Internals

    fileprivate struct LayoutInfo {

        static let stepperMinValue = CGFloat(0.0)

        static let stepperMaxValue = CGFloat(100.0)

        static let stepperStepSize = CGFloat(5.0)

    }

    var upButtonMouseDown = false

    var upButtonShowDepressed = false

    var downButtonMouseDown = false

    var downButtonShowDepressed = false

    var value = CGFloat(0.0) {

        didSet {

            if value < minValue {

                value = minValue

            }

            if value > maxValue {

                value = maxValue

            }

            needsDisplay = true

        }

    }

    var minValue = CGFloat(0.0)

    var maxValue = CGFloat(0.0)

    var stepSize = CGFloat(0.0)

    // MARK: - Metal Internals

    enum BufferIndices: Int {

        case vertices = 0

        case viewportSize

        case color

    }

    var trianglePipelineState: MTLRenderPipelineState?

    var backgroundPipelineState: MTLRenderPipelineState?

    var texture: MTLTexture?

    var commandQueue: MTLCommandQueue?

    var viewportSize: vector_uint2 = vector_uint2(0, 0)

    // MARK: - View Lifecycle

    required override init(frame frameRect: CGRect, device: MTLDevice?) {

        super.init(frame: frameRect, device: device)

        commonInit()

    }

    required init(coder: NSCoder) {

        super.init(coder: coder)

        commonInit()

    }

    fileprivate func commonInit() {

        loadMetal()

        minValue = LayoutInfo.stepperMinValue

        maxValue = LayoutInfo.stepperMaxValue

        stepSize = LayoutInfo.stepperStepSize

        // Register for mouse events that affect drawing.

        let trackingArea = NSTrackingArea(rect: bounds,

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

                                          owner: self,

                                          userInfo: nil)

        addTrackingArea(trackingArea)

    }

    // MARK: - Events

    // Set to allow keyDown to be called.

    override var acceptsFirstResponder: Bool { return true }

    var actionHandler: (() -> Void)?

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

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

            onCompletion()

        })

    }

    fileprivate func performIncrementButtonPress() {

        upButtonShowDepressed = true

        downButtonShowDepressed = false

        needsDisplay = true

        let delayInSeconds = 0.1

        performAfterDelay(delay: delayInSeconds) {

            self.upButtonShowDepressed = false

            self.downButtonShowDepressed = false

            self.needsDisplay = true

            self.increment()

        }

    }

    fileprivate func performDecrementButtonPress() {

        upButtonShowDepressed = false

        downButtonShowDepressed = true

        needsDisplay = true

        let delayInSeconds = 0.1

        performAfterDelay(delay: delayInSeconds) {

            self.upButtonShowDepressed = false

            self.downButtonShowDepressed = false

            self.needsDisplay = true

            self.decrement()

        }

    }

    fileprivate func increment() {

        value += stepSize

        actionHandler!()

    }

    fileprivate func decrement() {

        value -= stepSize

        actionHandler!()

    }

    // MARK: - Layout

    fileprivate func upButtonRect() -> NSRect {

        return NSRect(x: bounds.origin.x, y: bounds.midY, width: bounds.size.width, height: bounds.size.height / 2.0)

    }

    fileprivate func downButtonRect() -> NSRect {

        return NSRect(x: bounds.origin.x, y: bounds.origin.y, width: bounds.size.width, height: bounds.size.height / 2.0)

    }

    // MARK: - Mouse Events

    override func mouseDown(with event: NSEvent) {

        super.mouseDown(with: event)

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

        if upButtonRect().contains(mouseDownPoint) {

            upButtonMouseDown = true

            upButtonShowDepressed = true

            downButtonMouseDown = false

            downButtonShowDepressed = false

        } else if downButtonRect().contains(mouseDownPoint) {

            upButtonMouseDown = false

            upButtonShowDepressed = false

            downButtonMouseDown = true

            downButtonShowDepressed = true

        }

        needsDisplay = true

    }

    override func mouseUp(with event: NSEvent) {

        super.mouseUp(with: event)

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

        if upButtonMouseDown &&

            upButtonShowDepressed &&

            upButtonRect().contains(mouseUpPoint) {

            increment()

        } else if downButtonMouseDown &&

            downButtonShowDepressed &&

            downButtonRect().contains(mouseUpPoint) {

            decrement()

        }

        upButtonMouseDown = false

        upButtonShowDepressed = false

        downButtonMouseDown = false

        downButtonShowDepressed = false

        needsDisplay = true

    }

    override func mouseEntered(with event: NSEvent) {

        super.mouseEntered(with: event)

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

        if upButtonRect().contains(mousePoint) {

            upButtonShowDepressed = upButtonMouseDown

        } else if downButtonRect().contains(mousePoint) {

            downButtonShowDepressed = downButtonMouseDown

        }

        needsDisplay = true

    }

    override func mouseExited(with event: NSEvent) {

        super.mouseExited(with: event)

        upButtonShowDepressed = false

        downButtonShowDepressed = false

        needsDisplay = true

    }

    // MARK: - Keyboard Events

    override func keyDown(with event: NSEvent) {

        // Increment value on spacebar.

        if event.characters == " " {

            performIncrementButtonPress()

        } else {

            // Arrow keys are associated with the numeric keypad

            if event.modifierFlags.contains(.numericPad) {

                interpretKeyEvents([event])

            } else {

                super.keyDown(with: event)

            }

        }

    }

    override func moveUp(_ sender: Any?) {

        performIncrementButtonPress()

    }

    override func moveDown(_ sender: Any?) {

        performDecrementButtonPress()

    }

    // MARK: - MetalKit

    func loadMetal() {

        device = MTLCreateSystemDefaultDevice()

        do {

            // Indicate we would like to use the RGBAPixel format.

            colorPixelFormat = MTLPixelFormat.bgra8Unorm_srgb

            // Load all the shader files with a metal file extension in the project.

            let defaultLibrary = device!.makeDefaultLibrary()

            // Load the vertex function from the library.

            let vertexFunction = defaultLibrary!.makeFunction(name: "vertexShader")!

            // Set up a descriptor for creating a pipeline state object.

            let pipelineStateDescriptor = MTLRenderPipelineDescriptor()

            pipelineStateDescriptor.label = "colored triangle pipeline"

            pipelineStateDescriptor.vertexFunction = vertexFunction

            pipelineStateDescriptor.fragmentFunction = defaultLibrary!.makeFunction(name: "triangleFragmentShader")

            pipelineStateDescriptor.colorAttachments[0].pixelFormat = super.colorPixelFormat

            try trianglePipelineState = device!.makeRenderPipelineState(descriptor: pipelineStateDescriptor)

            pipelineStateDescriptor.label = "background quad pipeline"

            pipelineStateDescriptor.fragmentFunction = defaultLibrary!.makeFunction(name: "backgroundFragmentShader")

            try backgroundPipelineState = device!.makeRenderPipelineState(descriptor: pipelineStateDescriptor)

            let textureLoader = MTKTextureLoader(device: device!)

            try texture = textureLoader.newTexture(name: "Background", scaleFactor: 1.0, bundle: nil, options: nil)

            // Create the command queue.

            commandQueue = device?.makeCommandQueue()

        } catch {

            fatalError("Failed to setup Metal.")

        }

    }

    // MARK: - Drawing

    override func drawFocusRingMask() {

        bounds.fill()

    }

    override var focusRingMaskBounds: NSRect {

        return bounds

    }

    override func draw(_ dirtyRect: NSRect) {

        var whiteColor = vector_float4(1.0, 1.0, 1.0, 1.0)

        var pinkDiffusedColor = vector_float4(1.0, 0.0, 1.0, 1.0)

        var yellowDiffusedColor = vector_float4(1.0, 1.0, 0.0, 1.0)

        var halfViewportSize = vector_float2(Float(drawableSize.width) / 2.0,

                                             Float(drawableSize.height) / 2.0)

        var quadVertices: [Vertex] = [

            // Pixel Positions

            Vertex(position: vector_float4(x: -halfViewportSize.x, y: halfViewportSize.y, z: 0, w: 1),

                       // TexCoords

                texcoord: vector_float4(x: 0, y: 1, z: 0, w: 1)),

            Vertex(position: vector_float4(x: halfViewportSize.x, y: halfViewportSize.y, z: 0, w: 1),

                       texcoord: vector_float4(x: 1, y: 1, z: 0, w: 1)),

            Vertex(position: vector_float4(x: halfViewportSize.x, y: -halfViewportSize.y, z: 0, w: 1),

                       texcoord: vector_float4(x: 1, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: halfViewportSize.x, y: -halfViewportSize.y, z: 0, w: 1),

                       texcoord: vector_float4(x: 1, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: -halfViewportSize.x, y: -halfViewportSize.y, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: -halfViewportSize.x, y: halfViewportSize.y, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 1, z: 0, w: 1))

            ]

        var outlineVertices: [Vertex] = [

            // Note, value of texcoords doesn't matter as the pipeline these triangles are paired with don't

            // sample from a texture. (But we need to fill them in since the vertex shader expects them).

            // Top Triangle (Volume Up)

            Vertex(position: vector_float4(x: -halfViewportSize.x + 6, y: 4, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: 0, y: halfViewportSize.y - 3, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: halfViewportSize.x - 6, y: 4, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            // Bottom Triangle (Volume Down).

            Vertex(position: vector_float4(x: -halfViewportSize.x + 6, y: -4, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: halfViewportSize.x - 6, y: -4, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: 0, y: -halfViewportSize.y + 3, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1))

            ]

        var foregroundVertices: [Vertex] = [

            // Note, value of texcoords doesn't matter as the pipeline these triangles are paired with don't

            // sample from a texture. (But we need to fill them in since the vertex shader expects them).

            // Top Triangle (Volume Up).

            Vertex(position: vector_float4(x: -halfViewportSize.x + 9, y: 6, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: 0, y: halfViewportSize.y - 6, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: halfViewportSize.x - 9, y: 6, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            // Bottom Triangle (Volume Down).

            Vertex(position: vector_float4(x: -halfViewportSize.x + 9, y: -6, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: halfViewportSize.x - 9, y: -6, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1)),

            Vertex(position: vector_float4(x: 0, y: -halfViewportSize.y + 6, z: 0, w: 1),

                       texcoord: vector_float4(x: 0, y: 0, z: 0, w: 1))

            ]

        // Create a new command buffer for each renderpass to the current drawable.

        let commandBuffer = commandQueue?.makeCommandBuffer()

        commandBuffer?.label = "MyCommand"

        // Obtain a renderPassDescriptor generated from the view's drawable textures.

        let renderPassDescriptor = currentRenderPassDescriptor

        if let renderPassDescriptor = renderPassDescriptor {

            // Create a render command encoder so we can render into something.

            let renderEncoder = commandBuffer?.makeRenderCommandEncoder(descriptor: renderPassDescriptor)

            renderEncoder?.label = "MyRenderEncoder"

            renderEncoder?.setCullMode(.back)

            renderEncoder?.setRenderPipelineState(backgroundPipelineState!)

            renderEncoder?.setVertexBytes(quadVertices,

                                          length: MemoryLayout.size(ofValue: quadVertices[0]) * quadVertices.count,

                                          index: Int(BufferIndexVertices.rawValue))

            renderEncoder?.setVertexBytes(&halfViewportSize,

                                          length: MemoryLayout.size(ofValue: halfViewportSize),

                                          index: Int(BufferIndexViewportSize.rawValue))

            renderEncoder?.setFragmentTexture(texture, index: 0)

            renderEncoder?.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: 6)

            renderEncoder?.setRenderPipelineState(trianglePipelineState!)

            renderEncoder?.setVertexBytes(outlineVertices,

                                          length: MemoryLayout.size(ofValue: outlineVertices[0]) * outlineVertices.count,

                                          index: BufferIndices.vertices.rawValue)

            renderEncoder?.setFragmentBytes(&whiteColor,

                                            length: MemoryLayout<vector_float4>.size,

                                            index: BufferIndices.color.rawValue)

            // Draw or 2 triangles.

            renderEncoder?.drawPrimitives(type: .triangle, vertexStart:0, vertexCount:6)

            renderEncoder?.setVertexBytes(foregroundVertices,

                                          length: MemoryLayout.size(ofValue: foregroundVertices[0]) * foregroundVertices.count,

                                          index: BufferIndices.vertices.rawValue)

            // Draw upper triangle.

            if upButtonShowDepressed {

                renderEncoder?.setFragmentBytes(&pinkDiffusedColor,

                                                length: MemoryLayout.size(ofValue: pinkDiffusedColor),

                                                index: BufferIndices.color.rawValue)

            } else {

                renderEncoder?.setFragmentBytes(&yellowDiffusedColor,

                                                length: MemoryLayout.size(ofValue: yellowDiffusedColor),

                                                index: BufferIndices.color.rawValue)

            }

            renderEncoder?.drawPrimitives(type: .triangle, vertexStart:0, vertexCount:3)

            // Draw lower triangle.

            if downButtonShowDepressed {

                renderEncoder?.setFragmentBytes(&pinkDiffusedColor,

                                                length: MemoryLayout.size(ofValue: pinkDiffusedColor),

                                                index: BufferIndices.color.rawValue)

            } else {

                renderEncoder?.setFragmentBytes(&yellowDiffusedColor,

                                                length: MemoryLayout.size(ofValue: yellowDiffusedColor),

                                                index: BufferIndices.color.rawValue)

            }

            renderEncoder?.drawPrimitives(type: .triangle, vertexStart: 3, vertexCount: 3)

            renderEncoder?.endEncoding()

            if let drawable = currentDrawable {

                commandBuffer?.present(drawable)

            }

        }

        commandBuffer?.commit()

    }

}

// MARK: -

extension CustomStepperView {

    // MARK: NSAccessibilityStepper

    override func accessibilityLabel() -> String? {

        return NSLocalizedString("Volume", comment: "accessibility label for the volume stepper")

    }

    override func accessibilityHelp() -> String? {

        return NSLocalizedString("Adjusts the volume", comment: "accessibility help for the volume stepper")

    }

    override func accessibilityPerformIncrement() -> Bool {

        performIncrementButtonPress()

        return true

    }

    override func accessibilityPerformDecrement() -> Bool {

        performDecrementButtonPress()

        return true

    }

}