/*

 Copyright (C) 2017 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 A NSView subclass showing how to draw text using the Cocoa text system, and how render the view in Inteface Builder.

 */

import Cocoa

// CircleView draws text around a circle, using Cocoa's text system for

// glyph generation and layout, then calculating the positions of glyphs

// based on that layout, and using NSLayoutManager for drawing.

@IBDesignable

public class CircleView: NSView {

    var timer: Timer?

    var lastAnimationTime: TimeInterval = 0

    var center: NSPoint {

        didSet {

            self.needsDisplay = true

        }

    }

    var radius: CGFloat = 115.0 {

        didSet {

            self.needsDisplay = true

        }

    }

    var startingAngle: CGFloat = .pi / 2 {

        didSet {

            self.needsDisplay = true

        }

    }

    var angularVelocity: CGFloat = .pi / 2 {

        didSet {

            self.needsDisplay = true

        }

    }

    var string: String {

        get {

            return self.textStorage.string

        }

        set {

            self.textStorage.replaceCharacters(in: NSRange(location: 0, length:self.textStorage.length), with: newValue)

            self.needsDisplay = true

        }

    }

    let textStorage: NSTextStorage = NSTextStorage(string: "Here's to the crazy ones, the misfits, the rebels, the troublemakers, the round pegs in the square holes, the ones who see things differently.")

    let layoutManager: NSLayoutManager = NSLayoutManager()

    let textContainer: NSTextContainer = NSTextContainer()

    var textColor: NSColor = NSColor.black {

        didSet {

            // Text drawing uses the attributes set on the text storage rather

            // than drawing context attributes like the current color.

            let range = NSRange(location: 0, length: self.textStorage.length)

            self.textStorage.addAttribute(NSAttributedStringKey.foregroundColor, value: textColor, range: range)

            self.needsDisplay = true

        }

    }

    required public init?(coder: NSCoder) {

        // This initalizer is used when running the app, as well as when rendering the view as an IBDesignable

        // First, we set default values for the various parameters.

        self.center = NSPoint(x: 180, y: 135)

        super.init(coder: coder)

        // Setup the text system using NSTextStorage, NSLayoutManager, and NSTextContainer

        self.layoutManager.addTextContainer(self.textContainer)

        self.textStorage.addLayoutManager(self.layoutManager)

    }

    deinit {

        timer?.invalidate()

    }

    override public func draw(_ dirtyRect: NSRect) {

        super.draw(dirtyRect)

        NSColor.white.set()

        self.bounds.fill()

        // Note that usedRect(for:) does not force layout, so it must

        // be called after glyphRange(for:), which does force layout.

        let glyphRange = self.layoutManager.glyphRange(for: self.textContainer)

        let usedRect = self.layoutManager.usedRect(for: self.textContainer)

        for glyphIndex in glyphRange.location ..< NSMaxRange(glyphRange) {

            let context = NSGraphicsContext.current

            let lineFragmentRect = self.layoutManager.lineFragmentRect(forGlyphAt: glyphIndex, effectiveRange: nil)

            var layoutLocation = self.layoutManager.location(forGlyphAt: glyphIndex)

            let transform = NSAffineTransform()

            // Here layoutLocation is the location (in container coordinates) where the glyph was laid out.

            layoutLocation.x += lineFragmentRect.origin.x

            layoutLocation.y += lineFragmentRect.origin.y

            // We then use the layoutLocation to calculate an appropriate position for the glyph

            // around the circle (by angle and distance, or viewLocation in rectangular coordinates).

            let distance = self.radius + usedRect.size.height - layoutLocation.y

            let angle = self.startingAngle + layoutLocation.x / distance

            let viewLocationX = center.x + distance * sin(angle)

            let viewLocationY = center.y + distance * cos(angle)

            let viewLocation = NSPoint(x: viewLocationX, y: viewLocationY)

            // We use a different affine transform for each glyph, to position and rotate it

            // based on its calculated position around the circle.

            transform.translateX(by: viewLocation.x, yBy: viewLocation.y)

            transform.rotate(byRadians: -angle)

            // We save and restore the graphics state so that the transform applies only to this glyph.

            context?.saveGraphicsState()

            transform.concat()

            // drawGlyphs(forGlyphRange:at:) draws the glyph at its laid-out location in container coordinates.

            // Since we are using the transform to place the glyph, we subtract the laid-out location here.

            layoutManager.drawGlyphs(forGlyphRange: NSRange(location: glyphIndex, length:1), at: NSPoint(x: -layoutLocation.x, y: -layoutLocation.y))

            context?.restoreGraphicsState()

        }

    }

    override public var isOpaque: Bool {

        return false

    }

}

extension CircleView {

    private func startAnimation() {

        self.stopAnimation()

        // We schedule a timer for a desired 30fps animation rate.

        // In CircleView.animate(with:) we determine exactly how much time has elapsed and animate accordingly.

        timer = Timer.scheduledTimer(withTimeInterval: 1.0 / 30.0, repeats: true, block: { (timer) in

            self.animate(with: timer)

        })

        // The next two lines make sure that animation will continue to occur

        // while modal panels are displayed and while event tracking is taking

        // place (for example, while a slider is being dragged).

        RunLoop.current.add(timer!, forMode: .modalPanelRunLoopMode)

        RunLoop.current.add(timer!, forMode: .eventTrackingRunLoopMode)

        lastAnimationTime = Date.timeIntervalSinceReferenceDate

    }

    private func stopAnimation() {

        timer?.invalidate()

        timer = nil

    }

    func animate(with timer: Timer) {

        // We determine how much time has elapsed since the last animation,

        // and we advance the angle accordingly.

        let now = Date.timeIntervalSinceReferenceDate

        startingAngle = self.startingAngle + self.angularVelocity * CGFloat(now - lastAnimationTime)

        lastAnimationTime = now

    }

    func toggleAnimation() {

        if timer == nil {

            startAnimation()

        } else {

            stopAnimation()

        }

    }

}