import SwiftUI

public struct TextStyle: Equatable {
    public let family: FontFamily
    public let size: CGFloat
    public let weight: Int
    /// In em.
    public let tracking: CGFloat
    public let line: CGFloat
    public let caps: Bool
    public let tabular: Bool

    public init(family: FontFamily, size: CGFloat, weight: Int, tracking: CGFloat, line: CGFloat, caps: Bool, tabular: Bool) {
        self.family = family
        self.size = size
        self.weight = weight
        self.tracking = tracking
        self.line = line
        self.caps = caps
        self.tabular = tabular
    }

    var fontWeight: Font.Weight {
        switch weight {
        case ..<450: .regular
        case 450..<550: .medium
        case 550..<650: .semibold
        default: .bold
        }
    }

    public var font: Font {
        let base: Font
        switch family {
        case .mono: base = .system(size: size, weight: fontWeight, design: .monospaced)
        case .text: base = .system(size: size, weight: fontWeight)
        case .chrome: base = .custom(family.rawValue, size: size).weight(fontWeight)
        }
        return tabular ? base.monospacedDigit() : base
    }
}

public extension View {
    /// Font, tracking, line spacing and capitalisation from a token text style.
    func textStyle(_ style: TextStyle) -> some View {
        self.font(style.font)
            .tracking(style.tracking * style.size)
            .lineSpacing(max(0, style.line - style.size * 1.2))
            .textCase(style.caps ? .uppercase : nil)
    }
}

/// One layer of a layered shadow token. Inset layers are drawn inside the shape.
public struct ShadowLayer: Equatable {
    public let inset: Bool
    public let x: CGFloat
    public let y: CGFloat
    public let blur: CGFloat
    public let spread: CGFloat
    public let hex: UInt32
    public let alphaLight: Double
    public let alphaDark: Double

    public init(inset: Bool, x: CGFloat, y: CGFloat, blur: CGFloat, spread: CGFloat, hex: UInt32, alphaLight: Double, alphaDark: Double) {
        self.inset = inset
        self.x = x
        self.y = y
        self.blur = blur
        self.spread = spread
        self.hex = hex
        self.alphaLight = alphaLight
        self.alphaDark = alphaDark
    }

    public func color(_ scheme: ColorScheme) -> Color {
        Color.fixed(hex: hex).opacity(scheme == .dark ? alphaDark : alphaLight)
    }
}