import SwiftUI

extension Color {
    init(hex: UInt32, alpha: Double = 1) {
        self.init(.sRGB, red: Double((hex >> 16) & 0xFF) / 255, green: Double((hex >> 8) & 0xFF) / 255,
                  blue: Double(hex & 0xFF) / 255, opacity: alpha)
    }
}

/// The three themes' colours. Black is true black for OLED; no gradients anywhere.
struct Palette {
    var dark: Bool
    var bg: Color
    var groupedBg: Color
    var cell: Color
    var fill: Color
    var fillStrong: Color
    var label: Color
    var label2: Color
    var label3: Color
    var separator: Color
    var placeholder: Color
    var accent: Color
    var red: Color

    static func of(_ mode: ThemeMode, _ accent: Accent) -> Palette {
        switch mode {
        case .Black:
            Palette(dark: true, bg: Color(hex: 0x000000), groupedBg: Color(hex: 0x000000), cell: Color(hex: 0x1C1C1E),
                    fill: Color(hex: 0x1C1C1E), fillStrong: Color(hex: 0x3A3A3C), label: .white, label2: Color(hex: 0x8D8D93),
                    label3: Color(hex: 0x48484A), separator: Color(hex: 0x2C2C2E), placeholder: Color(hex: 0x1C1C1E),
                    accent: Color(hex: accent.dark), red: Color(hex: 0xFF453A))
        case .Dark:
            Palette(dark: true, bg: Color(hex: 0x1C1C1E), groupedBg: Color(hex: 0x1C1C1E), cell: Color(hex: 0x2C2C2E),
                    fill: Color(hex: 0x2C2C2E), fillStrong: Color(hex: 0x48484A), label: .white, label2: Color(hex: 0x98989D),
                    label3: Color(hex: 0x5A5A5E), separator: Color(hex: 0x3D3D40), placeholder: Color(hex: 0x3A3A3C),
                    accent: Color(hex: accent.dark), red: Color(hex: 0xFF453A))
        case .White:
            Palette(dark: false, bg: Color(hex: 0xFFFFFF), groupedBg: Color(hex: 0xF2F2F7), cell: Color(hex: 0xFFFFFF),
                    fill: Color(hex: 0xEFEFF0), fillStrong: Color(hex: 0xE3E3E8), label: .black, label2: Color(hex: 0x8A8A8E),
                    label3: Color(hex: 0xC4C4C7), separator: Color(hex: 0xD8D8DC), placeholder: Color(hex: 0xE5E5EA),
                    accent: Color(hex: accent.light), red: Color(hex: 0xFF3B30))
        }
    }
}

private struct PaletteKey: EnvironmentKey {
    static let defaultValue = Palette.of(.Black, .Music)
}

extension EnvironmentValues {
    var palette: Palette {
        get { self[PaletteKey.self] }
        set { self[PaletteKey.self] = newValue }
    }
}

extension View {
    /// A list on the theme's background instead of the system one.
    func themedList(grouped: Bool = true) -> some View { modifier(ThemedList(grouped: grouped)) }

    /// Rows on the theme's cell colour.
    func themedRow(grouped: Bool = true) -> some View { modifier(ThemedRow(grouped: grouped)) }
}

private struct ThemedList: ViewModifier {
    @Environment(\.palette) private var p
    let grouped: Bool
    func body(content: Content) -> some View {
        content.scrollContentBackground(.hidden).background(grouped ? p.groupedBg : p.bg)
    }
}

private struct ThemedRow: ViewModifier {
    @Environment(\.palette) private var p
    let grouped: Bool
    func body(content: Content) -> some View {
        content.listRowBackground(grouped ? p.cell : p.bg).listRowSeparatorTint(p.separator)
    }
}