import Foundation
import UIKit
import Display

final class PenTool: DrawingElement {
    class RenderLayer: SimpleLayer, DrawingRenderLayer {
        func setup(size: CGSize) {
            self.shouldRasterize = true
            self.contentsScale = 1.0
            
            let bounds = CGRect(origin: .zero, size: size)
            self.frame = bounds
        }
        
        private var line: StrokeLine?
        fileprivate func draw(line: StrokeLine, rect: CGRect) {
            self.line = line
            self.setNeedsDisplay(rect.insetBy(dx: -50.0, dy: -50.0))
        }
        
        override func draw(in ctx: CGContext) {
            self.line?.drawInContext(ctx)
        }
    }
    
    let uuid = UUID()
    
    let drawingSize: CGSize
    let color: DrawingColor
    let lineWidth: CGFloat
    let arrow: Bool
    
    var path: Polyline?
    var boundingBox: CGRect?
    
    private var renderLine: StrokeLine
    var didSetupArrow = false
    private var renderLineArrow1: StrokeLine?
    private var renderLineArrow2: StrokeLine?
    let renderLineWidth: CGFloat
    
    var translation = CGPoint()
    
    private var currentRenderLayer: DrawingRenderLayer?
    
    var bounds: CGRect {
        return self.path?.bounds.offsetBy(dx: self.translation.x, dy: self.translation.y) ?? .zero
    }
    
    var points: [Polyline.Point] {
        guard let linePath = self.path else {
            return []
        }
        var points: [Polyline.Point] = []
        for point in linePath.points {
            points.append(point.offsetBy(self.translation))
        }
        return points
    }
    
    func containsPoint(_ point: CGPoint) -> Bool {
        return false
        //        return self.renderPath?.contains(point.offsetBy(CGPoint(x: -self.translation.x, y: -self.translation.y))) ?? false
    }
    
    func hasPointsInsidePath(_ path: UIBezierPath) -> Bool {
        if let linePath = self.path {
            let pathBoundingBox = path.bounds
            if self.bounds.intersects(pathBoundingBox) {
                for point in linePath.points {
                    if path.contains(point.location.offsetBy(self.translation)) {
                        return true
                    }
                }
            }
        }
        return false
    }
    
    required init(drawingSize: CGSize, color: DrawingColor, lineWidth: CGFloat, arrow: Bool) {
        self.drawingSize = drawingSize
        self.color = color
        self.lineWidth = lineWidth
        self.arrow = arrow
        
        let minLineWidth = max(1.0, min(drawingSize.width, drawingSize.height) * 0.003)
        let maxLineWidth = max(10.0, min(drawingSize.width, drawingSize.height) * 0.09)
        let lineWidth = minLineWidth + (maxLineWidth - minLineWidth) * lineWidth
        
        self.renderLineWidth = lineWidth
        
        self.renderLine = StrokeLine(color: color.toUIColor(), minLineWidth: minLineWidth, lineWidth: lineWidth)
        if arrow {
            self.renderLineArrow1 = StrokeLine(color: color.toUIColor(), minLineWidth: minLineWidth, lineWidth: lineWidth * 0.8)
            self.renderLineArrow2 = StrokeLine(color: color.toUIColor(), minLineWidth: minLineWidth, lineWidth: lineWidth * 0.8)
        }
    }
    
    func setupRenderLayer() -> DrawingRenderLayer? {
        let layer = RenderLayer()
        layer.setup(size: self.drawingSize)
        self.currentRenderLayer = layer
        return layer
    }
    
    func updatePath(_ path: DrawingGesturePipeline.DrawingResult, state: DrawingGesturePipeline.DrawingGestureState) {
        guard case let .polyline(line) = path, let point = line.points.last else {
            return
        }
        self.path = line
        
        let rect = self.renderLine.draw(at: point)
        if let currentRenderLayer = self.currentRenderLayer as? RenderLayer {
            currentRenderLayer.draw(line: self.renderLine, rect: rect)
        }
        //        self.path = bezierPath
        
        //        if self.arrow && polyline.isComplete, polyline.points.count > 2 {
        //            let lastPoint = lastPosition
        //            var secondPoint = polyline.points[polyline.points.count - 2]
        //            if secondPoint.location.distance(to: lastPoint) < self.renderArrowLineWidth {
        //                secondPoint = polyline.points[polyline.points.count - 3]
        //            }
        //            let angle = lastPoint.angle(to: secondPoint.location)
        //            let point1 = lastPoint.pointAt(distance: self.renderArrowLength, angle: angle - CGFloat.pi * 0.15)
        //            let point2 = lastPoint.pointAt(distance: self.renderArrowLength, angle: angle + CGFloat.pi * 0.15)
        //
        //            let arrowPath = UIBezierPath()
        //            arrowPath.move(to: point2)
        //            arrowPath.addLine(to: lastPoint)
        //            arrowPath.addLine(to: point1)
        //            let arrowThickPath = arrowPath.cgPath.copy(strokingWithWidth: self.renderArrowLineWidth, lineCap: .round, lineJoin: .round, miterLimit: 0.0)
        //
        //            combinedPath.usesEvenOddFillRule = false
        //            combinedPath.append(UIBezierPath(cgPath: arrowThickPath))
        //        }
        
        //        let cgPath = bezierPath.path.cgPath.copy(strokingWithWidth: self.renderLineWidth, lineCap: .round, lineJoin: .round, miterLimit: 0.0)
        //        self.renderPath = cgPath
        
        //        if let currentRenderLayer = self.currentRenderLayer as? RenderLayer {
        //            currentRenderLayer.updatePath(cgPath)
        //        }
    }
    
    func draw(in context: CGContext, size: CGSize) {
        context.saveGState()
        
        context.translateBy(x: self.translation.x, y: self.translation.y)
        
        context.setShouldAntialias(true)
        
        if self.arrow, let path = self.path, let lastPoint = path.points.last {
            var lastPointWithVelocity: Polyline.Point?
            for point in path.points.reversed() {
                if point.velocity > 0.0 {
                    lastPointWithVelocity = point
                    break
                }
            }
            if !self.didSetupArrow, let lastPointWithVelocity = lastPointWithVelocity {
                let w = self.renderLineWidth
                var dist: CGFloat = 18.0 * sqrt(w)
                let spread: CGFloat = .pi * max(0.05, 0.03 * sqrt(w))
                
                let suffix = path.points.suffix(100).reversed()
                
                var p0 = suffix.first!
                
                var p2 = suffix.last!
                var d: CGFloat = 0
                for p in suffix {
                    d += hypot(p0.location.x - p.location.x, p0.location.y - p.location.y)
                    if d >= dist {
                        p2 = p
                        break
                    }
                    p0 = p
                }
                
                p0 = suffix.first!
                dist = min(dist, hypot(p0.location.x - p2.location.x, p0.location.y - p2.location.y))
                
                var i = 0
                for spread in [-spread, spread] {
                    var points: [CGPoint] = []
                    points.append(lastPoint.location)
                    
                    p0 = suffix.first!
                    var prev = p0.location
                    d = 0
                    for p in suffix {
                        let d1 = hypot(p0.location.x - p.location.x, p0.location.y - p.location.y)
                        d += d1
                        if d >= dist {
                            break
                        }
                        let d2 = d1 / cos(spread)
                        let angle = atan2(p.location.y - p0.location.y, p.location.x - p0.location.x)
                        let cur = CGPoint(x: prev.x + d2 * cos(angle + spread), y: prev.y + d2 * sin(angle + spread))
                        
                        points.append(
                            cur
                        )
                        
                        p0 = p
                        prev = cur
                    }
                    
                    for point in points {
                        if i == 0 {
                            let _ = self.renderLineArrow1?.draw(at: Polyline.Point(location: point, force: 0.0, altitudeAngle: 0.0, azimuth: 0.0, velocity: lastPointWithVelocity.velocity, touchPoint: lastPointWithVelocity.touchPoint))
                        } else if i == 1 {
                            let _ = self.renderLineArrow2?.draw(at: Polyline.Point(location: point, force: 0.0, altitudeAngle: 0.0, azimuth: 0.0, velocity: lastPointWithVelocity.velocity, touchPoint: lastPointWithVelocity.touchPoint))
                        }
                    }
                    i += 1
                }
                self.didSetupArrow = true
            }
            self.renderLineArrow1?.drawInContext(context)
            self.renderLineArrow2?.drawInContext(context)
        }
        
        self.renderLine.drawInContext(context)
        
        context.restoreGState()
    }
}

private class StrokeLine {
    struct Segment {
        let a: CGPoint
        let b: CGPoint
        let c: CGPoint
        let d: CGPoint
        let abWidth: CGFloat
        let cdWidth: CGFloat
    }
    
    struct Point {
        let position: CGPoint
        let width: CGFloat
        
        init(position: CGPoint, width: CGFloat) {
            self.position = position
            self.width = width
        }
    }
    
    private(set) var points: [Point] = []
    private var smoothPoints: [Point] = []
    private var segments: [Segment] = []
    private var lastWidth: CGFloat?
    
    private let minLineWidth: CGFloat
    let lineWidth: CGFloat
    
    let color: UIColor
    
    init(color: UIColor, minLineWidth: CGFloat, lineWidth: CGFloat) {
        self.color = color
        self.minLineWidth = minLineWidth
        self.lineWidth = lineWidth
    }
    
    func draw(at point: Polyline.Point) -> CGRect {
        let width = extractLineWidth(from: point.velocity)
        self.lastWidth = width
        
        let point = Point(position: point.location, width: width)
        return appendPoint(point)
    }
    
    func drawInContext(_ context: CGContext) {
        self.drawSegments(self.segments, inContext: context)
    }
    
    func extractLineWidth(from velocity: CGFloat) -> CGFloat {
        let minValue = self.minLineWidth
        let maxValue = self.lineWidth
        
        var size = max(minValue, min(maxValue + 1 - (velocity / 150), maxValue))
        if let lastWidth = self.lastWidth {
            size = size * 0.2 + lastWidth * 0.8
        }
        return size
    }
    
    func appendPoint(_ point: Point) -> CGRect {
        self.points.append(point)
        
        guard self.points.count > 2 else { return .null }
        
        let index = self.points.count - 1
        let point0 = self.points[index - 2]
        let point1 = self.points[index - 1]
        let point2 = self.points[index]
        
        let newSmoothPoints = smoothPoints(
            fromPoint0: point0,
            point1: point1,
            point2: point2
        )
        
        let lastOldSmoothPoint = smoothPoints.last
        smoothPoints.append(contentsOf: newSmoothPoints)
        
        guard smoothPoints.count > 1 else { return .null }
        
        let newSegments: ([Segment], CGRect) = {
            guard let lastOldSmoothPoint = lastOldSmoothPoint else {
                return segments(fromSmoothPoints: newSmoothPoints)
            }
            return segments(fromSmoothPoints: [lastOldSmoothPoint] + newSmoothPoints)
        }()
        segments.append(contentsOf: newSegments.0)
        
        return newSegments.1
    }
    
    func smoothPoints(fromPoint0 point0: Point, point1: Point, point2: Point) -> [Point] {
        var smoothPoints = [Point]()
        
        let midPoint1 = (point0.position + point1.position) * 0.5
        let midPoint2 = (point1.position + point2.position) * 0.5
        
        let segmentDistance = 2.0
        let distance = midPoint1.distance(to: midPoint2)
        let numberOfSegments = min(128, max(floor(distance/segmentDistance), 32))
        
        let step = 1.0 / numberOfSegments
        for t in stride(from: 0, to: 1, by: step) {
            let position = midPoint1 * pow(1 - t, 2) + point1.position * 2 * (1 - t) * t + midPoint2 * t * t
            let size = pow(1 - t, 2) * ((point0.width + point1.width) * 0.5) + 2 * (1 - t) * t * point1.width + t * t * ((point1.width + point2.width) * 0.5)
            let point = Point(position: position, width: size)
            smoothPoints.append(point)
        }
        
        let finalPoint = Point(position: midPoint2, width: (point1.width + point2.width) * 0.5)
        smoothPoints.append(finalPoint)
        
        return smoothPoints
    }
    
    func segments(fromSmoothPoints smoothPoints: [Point]) -> ([Segment], CGRect) {
        var segments = [Segment]()
        var updateRect = CGRect.null
        for i in 1 ..< smoothPoints.count {
            let previousPoint = smoothPoints[i - 1].position
            let previousWidth = smoothPoints[i - 1].width
            let currentPoint = smoothPoints[i].position
            let currentWidth = smoothPoints[i].width
            let direction = currentPoint - previousPoint
            
            guard !currentPoint.isEqual(to: previousPoint, epsilon: 0.0001) else {
                continue
            }
            
            var perpendicular = CGPoint(x: -direction.y, y: direction.x)
            let length = perpendicular.length
            if length > 0.0 {
                perpendicular = perpendicular / length
            }
            
            let a = previousPoint + perpendicular * previousWidth / 2
            let b = previousPoint - perpendicular * previousWidth / 2
            let c = currentPoint + perpendicular * currentWidth / 2
            let d = currentPoint - perpendicular * currentWidth / 2
            
            let ab: CGPoint = {
                let center = (b + a)/2
                let radius = center - b
                return .init(x: center.x - radius.y, y: center.y + radius.x)
            }()
            let cd: CGPoint = {
                let center = (c + d)/2
                let radius = center - c
                return .init(x: center.x + radius.y, y: center.y - radius.x)
            }()
            
            let minX = min(a.x, b.x, c.x, d.x, ab.x, cd.x)
            let minY = min(a.y, b.y, c.y, d.y, ab.y, cd.y)
            let maxX = max(a.x, b.x, c.x, d.x, ab.x, cd.x)
            let maxY = max(a.y, b.y, c.y, d.y, ab.y, cd.y)
            
            updateRect = updateRect.union(CGRect(x: minX, y: minY, width: maxX - minX, height: maxY - minY))
            
            segments.append(Segment(a: a, b: b, c: c, d: d, abWidth: previousWidth, cdWidth: currentWidth))
        }
        return (segments, updateRect)
    }
    
    func drawSegments(_ segments: [Segment], inContext context: CGContext) {
        for segment in segments {
            context.beginPath()

            context.setStrokeColor(color.cgColor)
            context.setFillColor(color.cgColor)
            
            context.move(to: segment.b)
            
            let abStartAngle = atan2(segment.b.y - segment.a.y, segment.b.x - segment.a.x)
            context.addArc(
                center: (segment.a + segment.b)/2,
                radius: segment.abWidth/2,
                startAngle: abStartAngle,
                endAngle: abStartAngle + .pi,
                clockwise: true
            )
            context.addLine(to: segment.c)
            
            let cdStartAngle = atan2(segment.c.y - segment.d.y, segment.c.x - segment.d.x)
            context.addArc(
                center: (segment.c + segment.d)/2,
                radius: segment.cdWidth/2,
                startAngle: cdStartAngle,
                endAngle: cdStartAngle + .pi,
                clockwise: true
            )
            context.closePath()
            
            context.fillPath()
            context.strokePath()
        }
    }
}