import { defineInjectable } from '@sigx/lynx';
import type { PrimitiveSignal } from '@sigx/reactivity';
import type { ColorScheme } from './types.js';

/** DI shape exposed by `<AppearanceProvider>`. */
export interface AppearanceContextValue {
  /** BG-side reactive color scheme. Re-renders consumers on system flip. */
  readonly colorScheme: PrimitiveSignal<ColorScheme>;
}

/**
 * The DI handle for the appearance context.
 *
 * Factory returns `null` so consumers outside a provider get a clear signal
 * (vs. a phantom `'light'` signal that silently never updates). Hooks in
 * `./hooks.ts` wrap this with the null-check + fallback signal.
 */
export const useAppearanceContext = defineInjectable<AppearanceContextValue | null>(
  () => null,
);