import Foundation
import SwiftUI

public enum ThemeMode: String, CaseIterable, Identifiable, Codable, Sendable {
  case system
  case light
  case dark

  public var id: String { rawValue }

  public var label: String {
    switch self {
    case .system: return "跟随系统"
    case .light: return "浅色"
    case .dark: return "深色"
    }
  }

  public var systemImage: String {
    switch self {
    case .system: return "circle.lefthalf.filled"
    case .light: return "sun.max"
    case .dark: return "moon.stars"
    }
  }
}

@MainActor
final class ThemeStore: ObservableObject {
  static let shared = ThemeStore()

  @Published private(set) var mode: ThemeMode
  private let defaults: UserDefaults
  private static let storageKey = "aiThemeMode"

  init(defaults: UserDefaults = .standard) {
    self.defaults = defaults
    mode = ThemeMode(rawValue: defaults.string(forKey: Self.storageKey) ?? "") ?? .system
  }

  func set(_ newMode: ThemeMode) {
    guard newMode != mode else { return }
    mode = newMode
    defaults.set(newMode.rawValue, forKey: Self.storageKey)
  }
}

extension ThemeMode {
  var colorScheme: ColorScheme? {
    switch self {
    case .system: return nil
    case .light: return .light
    case .dark: return .dark
    }
  }
}