import SwiftUI

/// 三角形方向
public enum TriangleDirection: Equatable {
    case up
    case down
    case left
    case right
}

/// 一个可插入(inset)的三角形 Shape，支持四个方向。
struct TriangleShape: InsettableShape {
    var direction: TriangleDirection = .up
    var insetAmount: CGFloat = 0

    var animatableData: CGFloat {
        get { insetAmount }
        set { insetAmount = newValue }
    }

    func inset(by amount: CGFloat) -> TriangleShape {
        var copy = self
        copy.insetAmount += amount
        return copy
    }

    func path(in rect: CGRect) -> Path {
        let r = rect.insetBy(dx: insetAmount, dy: insetAmount)

        // 顶点布局：根据方向决定三点位置
        let p1: CGPoint
        let p2: CGPoint
        let p3: CGPoint

        switch direction {
        case .up:
            p1 = CGPoint(x: r.midX, y: r.minY)
            p2 = CGPoint(x: r.maxX, y: r.maxY)
            p3 = CGPoint(x: r.minX, y: r.maxY)

        case .down:
            p1 = CGPoint(x: r.midX, y: r.maxY)
            p2 = CGPoint(x: r.minX, y: r.minY)
            p3 = CGPoint(x: r.maxX, y: r.minY)

        case .left:
            p1 = CGPoint(x: r.minX, y: r.midY)
            p2 = CGPoint(x: r.maxX, y: r.minY)
            p3 = CGPoint(x: r.maxX, y: r.maxY)

        case .right:
            p1 = CGPoint(x: r.maxX, y: r.midY)
            p2 = CGPoint(x: r.minX, y: r.maxY)
            p3 = CGPoint(x: r.minX, y: r.minY)
        }

        var path = Path()
        path.move(to: p1)
        path.addLine(to: p2)
        path.addLine(to: p3)
        path.closeSubpath()
        return path
    }
}

/// 可配置的三角形视图封装，便于在项目中复用。
/// 示例：
/// TriangleView(width: 20, height: 18, direction: .up, color: .black, stroke: .white, lineWidth: 2)
public struct TriangleView: View {
    public var width: CGFloat
    public var height: CGFloat
    public var direction: TriangleDirection
    public var color: Color
    public var stroke: Color? = nil
    public var lineWidth: CGFloat = 1
    public var rotation: Angle = .degrees(0)

    public init(
        width: CGFloat,
        height: CGFloat,
        direction: TriangleDirection = .up,
        color: Color = .black,
        stroke: Color? = nil,
        lineWidth: CGFloat = 1,
        rotation: Angle = .degrees(0)
    ) {
        self.width = width
        self.height = height
        self.direction = direction
        self.color = color
        self.stroke = stroke
        self.lineWidth = lineWidth
        self.rotation = rotation
    }

    public var body: some View {
        let shape = TriangleShape(direction: direction)
        Group {
            if let stroke = stroke, lineWidth > 0 {
                shape.fill(color)
                    .overlay(
                        shape.stroke(stroke, lineWidth: lineWidth)
                    )
            } else {
                shape.fill(color)
            }
        }
        .frame(width: width, height: height)
        .rotationEffect(rotation)
        .accessibilityHidden(true)
    }
}

/// 水平渲染多个等尺寸三角形的小组件。
public struct TriangleRow: View {
    public var count: Int
    public var itemSize: CGSize
    public var direction: TriangleDirection
    public var color: Color
    public var spacing: CGFloat
    public var rotation: Angle

    public init(
        count: Int,
        itemSize: CGSize,
        direction: TriangleDirection = .up,
        color: Color = .black,
        spacing: CGFloat = 8,
        rotation: Angle = .degrees(0)
    ) {
        self.count = count
        self.itemSize = itemSize
        self.direction = direction
        self.color = color
        self.spacing = spacing
        self.rotation = rotation
    }

    public var body: some View {
        HStack(spacing: spacing) {
            ForEach(0..<(max(0, count)), id: \.self) { _ in
                TriangleView(
                    width: itemSize.width,
                    height: itemSize.height,
                    direction: direction,
                    color: color,
                    rotation: rotation
                )
            }
        }
        .accessibilityElement(children: .ignore)
    }
}

#if DEBUG
struct Triangle_Previews: PreviewProvider {
    static var previews: some View {
        Group {
            // 单个三角形
            TriangleView(width: 24, height: 20, direction: .up, color: .black, stroke: .white, lineWidth: 2)
                .padding()
                .previewDisplayName("Single Up")

            TriangleView(width: 24, height: 20, direction: .right, color: .orange)
                .padding()
                .background(Color(.systemGroupedBackground))
                .previewDisplayName("Single Right")

            TriangleView(width: 24, height: 20, direction: .up, color: .blue, rotation: .degrees(132))
                .padding()
                .previewDisplayName("Rotated 132")

            // 行展示
            ZStack {
                Color(white: 0.97)
                HStack {
                    RoundedRectangle(cornerRadius: 18, style: .continuous)
                        .fill(.white)
                        .shadow(color: Color.black.opacity(0.06), radius: 6, x: 0, y: 2)
                        .overlay(
                            HStack {
                                TriangleRow(
                                    count: 6,
                                    itemSize: CGSize(width: 16, height: 14),
                                    direction: .up,
                                    color: .black,
                                    spacing: 6,
                                    rotation: .degrees(180)
                                )
                            }
                            .padding(.horizontal, 18)
                        )
                        .frame(height: 64)
                        .padding()
                }
            }
            .previewDisplayName("Row")
        }
        .previewLayout(.sizeThatFits)
    }
}
#endif