import SwiftUI

enum JSColorParser {
  /// Parses Hex, RGB, RGBA, HSL, HSLA, and named color strings into SwiftUI Color.
  static func parse(_ value: Any?) -> Color? {
    guard let string = value as? String else { return nil }

    // Optimize: standard trim and lowercase
    let trimmed = string.trimmingCharacters(in: .whitespacesAndNewlines).lowercased()

    if trimmed.isEmpty { return nil }

    // 1. Hex (with or without #)
    if trimmed.hasPrefix("#") {
      return parseHex(trimmed)
    }

    // Check for hex without # prefix (6 or 8 hex digits)
    if isHexColor(trimmed) {
      return parseHex("#" + trimmed)
    }

    // 2. RGB / RGBA
    if trimmed.hasPrefix("rgb") {
      return parseRGB(trimmed)
    }

    // 3. HSL / HSLA
    if trimmed.hasPrefix("hsl") {
      return parseHSL(trimmed)
    }

    // 4. Named colors
    if let namedColor = parseNamedColor(trimmed) {
      return namedColor
    }

    return nil
  }

  /// Check if a string is a valid hex color (6 or 8 hex digits)
  private static func isHexColor(_ string: String) -> Bool {
    guard string.count == 6 || string.count == 8 else { return false }
    // Check if all characters are valid hex digits (0-9, a-f)
    let hexChars = CharacterSet(charactersIn: "0123456789abcdef")
    return string.unicodeScalars.allSatisfy { hexChars.contains($0) }
  }

  /// Parse named color strings
  private static func parseNamedColor(_ name: String) -> Color? {
    switch name {
    case "red":
      return .red
    case "orange":
      return .orange
    case "yellow":
      return .yellow
    case "green":
      return .green
    case "mint":
      if #available(iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0, *) {
        return .mint
      }
      return .primary
    case "teal":
      if #available(iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0, *) {
        return .teal
      }
      return .primary
    case "cyan":
      if #available(iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0, *) {
        return .cyan
      }
      return .primary
    case "blue":
      return .blue
    case "indigo":
      if #available(iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0, *) {
        return .indigo
      }
      return .primary
    case "purple":
      return .purple
    case "pink":
      return .pink
    case "brown":
      if #available(iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0, *) {
        return .brown
      }
      return .primary
    case "white":
      return .white
    case "gray":
      return .gray
    case "black":
      return .black
    case "clear", "transparent":
      return .clear
    case "primary":
      return .primary
    case "secondary":
      return .secondary
    default:
      return nil
    }
  }

  // MARK: - Hex Parser

  // Supports #RGB, #RGBA, #RRGGBB, #RRGGBBAA
  private static func parseHex(_ hex: String) -> Color? {
    let hexSanitized = hex.replacingOccurrences(of: "#", with: "")

    var rgb: UInt64 = 0
    Scanner(string: hexSanitized).scanHexInt64(&rgb)

    let r, g, b, a: Double
    let length = hexSanitized.count

    switch length {
    case 3: // #RGB
      r = Double((rgb >> 8) & 0xF) / 15.0
      g = Double((rgb >> 4) & 0xF) / 15.0
      b = Double(rgb & 0xF) / 15.0
      a = 1.0
    case 4: // #RGBA
      r = Double((rgb >> 12) & 0xF) / 15.0
      g = Double((rgb >> 8) & 0xF) / 15.0
      b = Double((rgb >> 4) & 0xF) / 15.0
      a = Double(rgb & 0xF) / 15.0
    case 6: // #RRGGBB
      r = Double((rgb >> 16) & 0xFF) / 255.0
      g = Double((rgb >> 8) & 0xFF) / 255.0
      b = Double(rgb & 0xFF) / 255.0
      a = 1.0
    case 8: // #RRGGBBAA
      r = Double((rgb >> 24) & 0xFF) / 255.0
      g = Double((rgb >> 16) & 0xFF) / 255.0
      b = Double((rgb >> 8) & 0xFF) / 255.0
      a = Double(rgb & 0xFF) / 255.0
    default:
      return nil
    }

    return Color(.sRGB, red: r, green: g, blue: b, opacity: a)
  }

  // MARK: - RGB Parser

  // rgb(255, 0, 0) / rgba(255, 0, 0, 0.5)
  private static func parseRGB(_ string: String) -> Color? {
    let cleaned = string
      .replacingOccurrences(of: "rgba", with: "")
      .replacingOccurrences(of: "rgb", with: "")
      .replacingOccurrences(of: "(", with: "")
      .replacingOccurrences(of: ")", with: "")
      .replacingOccurrences(of: " ", with: "")

    let components = cleaned.split(separator: ",")
    guard components.count >= 3 else { return nil }

    let r = Double(components[0]) ?? 0
    let g = Double(components[1]) ?? 0
    let b = Double(components[2]) ?? 0
    let a = components.count >= 4 ? (Double(components[3]) ?? 1.0) : 1.0

    return Color(.sRGB, red: r / 255.0, green: g / 255.0, blue: b / 255.0, opacity: a)
  }

  // MARK: - HSL Parser

  // hsl(120, 100%, 50%) / hsla(...)
  private static func parseHSL(_ string: String) -> Color? {
    let cleaned = string
      .replacingOccurrences(of: "hsla", with: "")
      .replacingOccurrences(of: "hsl", with: "")
      .replacingOccurrences(of: "(", with: "")
      .replacingOccurrences(of: ")", with: "")
      .replacingOccurrences(of: " ", with: "")
      .replacingOccurrences(of: "%", with: "")

    let components = cleaned.split(separator: ",")
    guard components.count >= 3 else { return nil }

    let h = (Double(components[0]) ?? 0) / 360.0
    let s = (Double(components[1]) ?? 0) / 100.0
    let l = (Double(components[2]) ?? 0) / 100.0
    let a = components.count >= 4 ? (Double(components[3]) ?? 1.0) : 1.0

    // Convert HSL to RGB (HSL != HSB/HSV)
    let (r, g, b) = hslToRgb(h: h, s: s, l: l)
    return Color(.sRGB, red: r, green: g, blue: b, opacity: a)
  }

  /// Convert HSL to RGB
  /// - Parameters:
  ///   - h: Hue (0.0 to 1.0)
  ///   - s: Saturation (0.0 to 1.0)
  ///   - l: Lightness (0.0 to 1.0)
  /// - Returns: RGB tuple with values from 0.0 to 1.0
  private static func hslToRgb(h: Double, s: Double, l: Double) -> (r: Double, g: Double, b: Double) {
    // Achromatic case (no saturation)
    if s == 0 {
      return (l, l, l)
    }

    let q = l < 0.5 ? l * (1 + s) : l + s - l * s
    let p = 2 * l - q

    let r = hueToRgb(p: p, q: q, t: h + 1.0 / 3.0)
    let g = hueToRgb(p: p, q: q, t: h)
    let b = hueToRgb(p: p, q: q, t: h - 1.0 / 3.0)

    return (r, g, b)
  }

  /// Helper function for HSL to RGB conversion
  private static func hueToRgb(p: Double, q: Double, t: Double) -> Double {
    var t = t
    if t < 0 { t += 1 }
    if t > 1 { t -= 1 }

    if t < 1.0 / 6.0 { return p + (q - p) * 6 * t }
    if t < 1.0 / 2.0 { return q }
    if t < 2.0 / 3.0 { return p + (q - p) * (2.0 / 3.0 - t) * 6 }
    return p
  }
}