import Foundation
import UIKit

class CurveText: UIView, UIGestureRecognizerDelegate, UITextViewDelegate {
    var tf = UITextView()
    private let shadowLayer = CALayer()
    private let textLayer = CALayer()
    private let defaultTextViewLeftInset = CGFloat(5)
    private let defaultTextViewRightInset = CGFloat(5)

    var curvePattern = (CGPoint(x: 0, y: 0), CGPoint(x: 90, y: 50), CGPoint(x: 180, y: 0)) {
        didSet {
            curve = curvePattern
            setNeedsLayout()
        }
    }
    var curve = (CGPoint(x: 0, y: 0), CGPoint(x: 90, y: 50), CGPoint(x: 180, y: 0))

    var min = CGFloat(20) { didSet { setNeedsLayout() } }
    var max = CGFloat(40) { didSet { setNeedsLayout() } }
    var maxPosition: CGFloat = 0 { didSet { setNeedsLayout() } } // 0...1

    let minCharsForStartCalculating = 3

    var textColor = UIColor.white { didSet { setNeedsDisplay() } }
    var shadowOffset = CGPoint(x: 1, y: 0) { didSet { setNeedsDisplay() } }
    var shadowBlur = CGFloat(0) { didSet { setNeedsDisplay() } }
    var shadowWeight = CGFloat(1) { didSet { setNeedsDisplay() } }
    var shadowColor = UIColor.black { didSet { setNeedsDisplay() } }

    var text: String = "Psssh" { didSet { setNeedsLayout() } }

    var font: UIFont = UIFont.systemFont(ofSize: 1) { didSet { setNeedsLayout() } }

    func update() {
        let newString = self.text
        let attrStr = NSMutableAttributedString(string: newString)

        attrStr.addAttributes([
            NSForegroundColorAttributeName: UIColor.red.withAlphaComponent(0),
            NSKernAttributeName: 0
        ], range: NSRange(location: 0, length: attrStr.length))

        for (index, _) in newString.characters.enumerated() {
            let base = CGFloat([newString.characters.count, minCharsForStartCalculating].max()!) - 1

            var radius: CGFloat
            radius = [1 - maxPosition, maxPosition][base * maxPosition - CGFloat(index) < 0 ? 0 : 1]
            //radius = [1 - maxPosition, maxPosition].max()!
            radius = [1, radius * base].max()!
            let koef = abs(base * maxPosition - CGFloat(index)) / radius
            let fontSize = CGFloat(Int(CGFloat(max - min) * (1 - koef) + CGFloat(min) * 5) / 5)

            //let fontSize = CGFloat((1 - CGFloat(index) / CGFloat(newValue.characters.count)) * (CGFloat(max) - CGFloat(min)) + CGFloat(min))
            let font = self.font.withSize(fontSize)

            attrStr.addAttribute(NSFontAttributeName, value: font, range: NSRange(location: index, length: 1))
        }

        let l = length(CGPoint(x: curve.0.x, y: 0), CGPoint(x: curve.2.x, y: 0))
        if newString.count >= minCharsForStartCalculating || l <= 10 {
            curve.2 = interpolate(curve.0, curve.2, attrStr.size().width / l)
            curve.1 = interpolate(curve.0, curve.1, attrStr.size().width / l)
        }

        var baselineGlobalOffset: CGFloat = 0
        var currentXPosition = CGFloat(0)
        for (index, char) in newString.characters.enumerated() {
            let charAttrs = attrStr.attributes(at: index, effectiveRange: nil)
            let font = charAttrs[NSFontAttributeName] as! UIFont

            let charSize = NSString(string: String(char)).size(attributes: charAttrs)
            let baselineOffset = -(quadraticBezier(curve, rootsQuadraticBezier(curve, currentXPosition + charSize.width / 2).0).y)

            baselineGlobalOffset = [font.ascender + [baselineOffset, 0].max()!, baselineGlobalOffset].max()!

            attrStr.addAttribute(NSBaselineOffsetAttributeName, value: baselineOffset, range: NSRange(location: index, length: 1))
            currentXPosition += charSize.width

            var unichars = [UniChar](String(char).utf16)
            var glyphs = [CGGlyph](repeating: 0, count: unichars.count)
            var boundingRects = [CGRect](repeating: .zero, count: unichars.count)
            var advances = [CGSize](repeating: .zero, count: unichars.count)

            let gotGlyphs = CTFontGetGlyphsForCharacters(font, &unichars, &glyphs, unichars.count)
            let _ = CTFontGetBoundingRectsForGlyphs(font as CTFont, .horizontal, glyphs, &boundingRects, unichars.count)
            let _ = CTFontGetAdvancesForGlyphs(font as CTFont, .horizontal, glyphs, &advances, unichars.count)

            attrStr.addAttribute("advance", value: advances.first!, range: NSRange(location: index, length: 1))
            attrStr.addAttribute("boundingRect", value: boundingRects.first!, range: NSRange(location: index, length: 1))
            attrStr.addAttribute("glyph", value: glyphs.first!, range: NSRange(location: index, length: 1))

            if gotGlyphs {
                for glyph in glyphs {
                    var matrix = CGAffineTransform.identity
                    if let path = CTFontCreatePathForGlyph(font as CTFont, glyph, &matrix) {
                        attrStr.addAttribute("path", value: path, range: NSRange(location: index, length: 1))
                    }
                }
            }
        }

        let selection = tf.selectedTextRange
        tf.attributedText = attrStr
        tf.selectedTextRange = selection

        tf.bounds.size = attrStr.size()
        tf.frame.origin.y = -baselineGlobalOffset
        tf.frame.origin.x = 0
        tf.frame = tf.frame.insetBy(dx: -(defaultTextViewLeftInset + defaultTextViewRightInset) / 2, dy: 0)
    }

    private func updateVector(_ attrStr: NSMutableAttributedString) {
        let glyphsPath = CGMutablePath()

        var advancesSum = CGFloat(0)

        for (index, _) in self.text.enumerated() {
//            let font = attrStr.attribute(NSFontAttributeName, at: index, effectiveRange: nil) as! UIFont
            let baselineOffset = attrStr.attribute(NSBaselineOffsetAttributeName, at: index, effectiveRange: nil) as! CGFloat
            let kern = attrStr.attribute(NSKernAttributeName, at: index, effectiveRange: nil) as? CGFloat ?? 0

            let boundingRect = attrStr.attribute("boundingRect", at: index, effectiveRange: nil) as! CGRect
            let advance = attrStr.attribute("advance", at: index, effectiveRange: nil) as! CGSize
            //let glyph = attrStr.attribute("glyph", at: index, effectiveRange: nil) as! CGGlyph

            let path = attrStr.attribute("path", at: index, effectiveRange: nil) as! CGPath?

            var prevBaseline: CGFloat? = nil
            var prevAdvance: CGSize? = nil
            if 0..<self.text.count ~= (index - 1) {
                prevBaseline = attrStr.attribute(NSBaselineOffsetAttributeName, at: index - 1, effectiveRange: nil) as? CGFloat
                prevAdvance = attrStr.attribute("advance", at: index - 1, effectiveRange: nil) as? CGSize
            }
            var nextBaseline: CGFloat? = nil
            if 0..<self.text.count ~= (index + 1) {
                prevBaseline = attrStr.attribute(NSBaselineOffsetAttributeName, at: index + 1, effectiveRange: nil) as? CGFloat
            }

            var angle = CGFloat(0)
            let point1: CGPoint
            let point2: CGPoint
            if let prevBaseline = prevBaseline, let prevAdvance = prevAdvance {
                point1 = CGPoint(x: advancesSum - prevAdvance.width / 2, y: prevBaseline)
                point2 = CGPoint(x: advancesSum + advance.width / 2, y: -baselineOffset)
            } else {
                point1 = CGPoint(x: curve.0.x, y: curve.0.y)
                point2 = CGPoint(x: advancesSum + advance.width / 2, y: -baselineOffset)
            }
            angle = CGFloat(atan2(Double(point2.y - point1.y), Double(point2.x - point1.x))) + CGFloat.pi / 2

            if let path = path {
                let matrix = CGAffineTransform.identity.translatedBy(x: advancesSum, y: -baselineOffset).scaledBy(x: 1, y: -1).rotated(by: angle)
                glyphsPath.addPath(path, transform: matrix)
                let rect = CGMutablePath()
                var copyMatrix = matrix.rotated(by: angle * 2)
                let copyPath = path.copy(using: &copyMatrix)!
                rect.addRect(copyPath.boundingBoxOfPath)
                glyphsPath.addPath(rect)
            }
            advancesSum += advance.width + kern
        }

        shadowLayer.sublayers?.forEach{ $0.removeFromSuperlayer() }
        if shadowWeight > 0 {
            let shadowSprite = CALayer()
            let strokeLayer = CAShapeLayer()
            strokeLayer.strokeColor = UIColor.black.cgColor
            strokeLayer.lineWidth = shadowWeight * 2
            strokeLayer.lineCap = kCALineCapRound
            strokeLayer.lineJoin = kCALineJoinRound
            strokeLayer.path = glyphsPath
            strokeLayer.lineDashPattern = [NSNumber(floatLiteral: Double.infinity), 0]
            shadowSprite.addSublayer(strokeLayer)

            let fillLayer = CAShapeLayer()
            fillLayer.fillColor = UIColor.black.cgColor
            fillLayer.path = glyphsPath
            shadowSprite.addSublayer(fillLayer)

            shadowSprite.shadowColor = shadowColor.cgColor
            let dropCoord = CGFloat(1000)
            shadowSprite.shadowOffset = CGSize(width: self.shadowOffset.x + dropCoord, height: self.shadowOffset.y)
            shadowSprite.shadowRadius = self.shadowBlur
            shadowSprite.shadowOpacity = 1
            shadowSprite.frame.origin.x -= dropCoord

            shadowLayer.addSublayer(shadowSprite)
        }

        let textShape = CAShapeLayer()

        textShape.fillColor = textColor.cgColor
        textShape.path = glyphsPath
        textLayer.sublayers?.forEach{ $0.removeFromSuperlayer() }
        textLayer.addSublayer(textShape)

        let lineShape = CAShapeLayer()
        lineShape.strokeColor = UIColor.black.cgColor
        lineShape.lineWidth = 1
        lineShape.fillColor = nil
        let linePath = CGMutablePath()
        linePath.move(to: curve.0)
        linePath.addQuadCurve(to: curve.2, control: curve.1)
        lineShape.path = linePath
        textLayer.addSublayer(lineShape)

        self.textLayer.removeAllAnimations()
        self.shadowLayer.removeAllAnimations()
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
        return self.frame.contains(point) || self.tf.frame.contains(point)
    }

    convenience init() {
        self.init(frame: .zero)
        self.backgroundColor = .white

        tf.delegate = self
        tf.backgroundColor = nil
        tf.textContainerInset = .zero
        tf.isScrollEnabled = false
        tf.scrollIndicatorInsets = .zero
        tf.showsVerticalScrollIndicator = false
        tf.showsHorizontalScrollIndicator = false
        tf.clipsToBounds = false
        self.addSubview(tf)


        self.layer.insertSublayer(shadowLayer, at: 0)
        self.layer.insertSublayer(textLayer, at: 1)


//        let shape = CAShapeLayer()
//
//        shape.lineWidth = 1
//        shape.lineCap = kCALineCapRound
//        shape.fillColor = nil
//        shape.strokeColor = UIColor.black.cgColor
//        self.layer.insertSublayer(shape, at: 2)
//
//        var angle = CGFloat(1);
//        Timer.scheduledTimer(withTimeInterval: 1 / 60, repeats: true, block: {
//            _ in
//
//            angle -= 0.04
//            if angle < -0.5 {
//                //return
//            }
//            let path = CGMutablePath()
//            path.move(to: self.curve.0)
//            path.addQuadCurve(to: self.curve.2, control: self.curve.1)
//            self.curve.1.y += sin(angle) * 3
//            //self.curve.2.y -= sin(angle) / 4
//            self.curve.0.y -= sin(angle) / 4
//            self.text = (self.text + "")
//            self.setNeedsDisplay()
//
//            shape.path = path
//        })
    }

    override func draw(_ rect: CGRect) {
        updateVector(NSMutableAttributedString(attributedString: tf.attributedText))
    }

    override func layoutSubviews() {
        update()
        setNeedsDisplay()
    }

    func textViewDidChange(_ textView: UITextView) {
        self.text = textView.text
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

func pointAtBrokenLine(_ points: [CGPoint], position: CGFloat) -> (CGPoint, CGPoint)? {
    var sumLength: CGFloat = 0

    guard points.count > 1 else {
        return nil
    }
    guard position > 0 else {
        return (points[0], halfVec(points[1], points[0], points[1]))
    }

    var prevPoint: CGPoint = points.first!

    for i in 1..<points.count {
        let point = points[i]
        let len = length(prevPoint, point)

        if sumLength + len == position || i == points.count - 1 && (position - sumLength - len < CGFloat.ulpOfOne * CGFloat(points.count)) {
            let nextPoint = i < points.count - 1 ? points[i + 1] : prevPoint

            if (nextPoint != prevPoint) {
                return (point, CGPoint(x: (point.x - prevPoint.x) / len, y: (point.y - prevPoint.y) / len))
            }

            return (point, halfVec(prevPoint, point, nextPoint))
        }

        if sumLength + len > position {
            return (interpolate(prevPoint, point, (position - sumLength) / len), CGPoint(x: -(prevPoint.y - point.y) / len, y: (prevPoint.x - point.x) / len ))
        }

        sumLength += len
        prevPoint = point
    }

    return nil
}

func halfVec(_ p1: CGPoint, _ p2: CGPoint, _ p3: CGPoint) -> CGPoint {
    var halfPoint = CGPoint(
        x: (p1.x - p2.x) + (p1.x - p3.x),
        y: (p1.y - p2.y) + (p1.y - p3.y)
    )

    if skewProduct(sub(p1, p2), sub(p2, p3)) >= 0 {
        halfPoint.x *= -1
        halfPoint.y *= -1
    }
    let len = length(halfPoint, p2)
    halfPoint.x /= len
    halfPoint.y /= len
    return halfPoint
}

func quadraticBezierToBrokenLine(_ points: (CGPoint, CGPoint, CGPoint), quality: CGFloat = 1) -> [CGPoint] {
    guard CGFloat.ulpOfOne...1 ~= quality else {
        return [points.0, points.1, points.2]
    }
    let step = (1 / quality) / (length(points.0, points.1) + length(points.1, points.2))

    return stride(from: 0, to: 1, by: step).map{
        return quadraticBezier(points, $0)
        } + [points.2]
}

func rootsQuadraticBezier(_ points: (CGPoint, CGPoint, CGPoint), _ x: CGFloat) -> (CGFloat, CGFloat) {
    let a = [points.2.x - points.1.x * 2 + points.0.x, 1].max()!
    let b = 2 * (points.1.x - points.0.x)
    let c = points.0.x - x

    let d = b * b - 4 * a * c

    return (
        (-b + sqrt(d)) / (2 * a),
        (-b - sqrt(d)) / (2 * a)
    )
}

func rootLine(_ points: (CGPoint, CGPoint), _ x: CGFloat) -> CGFloat {
    return (x - points.0.x) / (points.1.x - points.0.x)
}

func quadraticBezier(_ points: (CGPoint, CGPoint, CGPoint), _ t: CGFloat) -> CGPoint {
    return CGPoint(x: quadraticBezier((points.0.x, points.1.x, points.2.x), t), y: quadraticBezier((points.0.y, points.1.y, points.2.y), t))
}

func quadraticBezier(_ points: (CGFloat, CGFloat, CGFloat), _ t: CGFloat) -> CGFloat {
    return points.0 + t * (t * (points.2 - points.1 * 2 + points.0) + 2 * (points.1 - points.0));
}

func skewProduct(_ p1: CGPoint, _ p2: CGPoint) -> CGFloat {
    return p1.x * p2.y - p2.x * p1.y
}

func sub(_ p1: CGPoint, _ p2: CGPoint) -> CGPoint {
    return CGPoint(x: p1.x - p2.x, y: p1.y - p2.y)
}

func add(_ p1: CGPoint, _ p2: CGPoint) -> CGPoint {
    return CGPoint(x: p1.x + p2.x, y: p1.y + p2.y)
}

func length(_ points: [CGPoint]) -> CGFloat? {
    guard points.count > 1 else { return nil }
    return points.reduce((points.first!, CGFloat(0)), {
        return ($1, $0.1 + length($0.0, $1))
    }).1
}

func length(_ p1: CGPoint, _ p2: CGPoint) -> CGFloat {
    return length(CGPoint(x: p2.x - p1.x, y: p2.y - p1.y))
}

func length(_ p: CGPoint) -> CGFloat {
    return (p.x * p.x + p.y * p.y).squareRoot()
}

func interpolate(_ p1: CGPoint, _ p2: CGPoint, _ t: CGFloat) -> CGPoint {
    return CGPoint(x: (p2.x - p1.x) * t + p1.x, y: (p2.y - p1.y) * t + p1.y)
}