export type Theme = 'light' | 'dark';

export interface WidgetHost {
  readonly element: HTMLElement;
  readonly instanceId: string;
}

export interface ConfigApi<T> {
  get(): T;
  set(value: Partial<T>): Promise<void>;
  onChange(handler: (value: T) => void): () => void;
}

export interface SystemApi {
  getTheme(): Theme;
  onThemeChange(handler: (theme: Theme) => void): () => void;
}

export interface LifecycleApi {
  onMount(handler: () => void): void;
  onUnmount(handler: () => void): void;
  onVisibilityChange(handler: (visible: boolean) => void): () => void;
}

export interface ShellApi {
  call<T = unknown>(method: string, args?: unknown): Promise<T>;
}

export interface WidgetContext<T> {
  config: ConfigApi<T>;
  system: SystemApi;
  lifecycle: LifecycleApi;
  shell: ShellApi;
}

export interface WidgetDefinition<T> {
  id: string;
  defaultConfig: T;
  mount(host: WidgetHost, ctx: WidgetContext<T>): void;
  configUI?(host: WidgetHost, ctx: WidgetContext<T>): void;
}