export type VMStatus = "idle" | "loading" | "ready" | "empty" | "error";

export type VMState<T> =
  | { status: "idle"; data?: undefined; error?: undefined }
  | { status: "loading"; data?: T; error?: undefined }
  | { status: "ready"; data: T; error?: undefined }
  | { status: "empty"; data?: undefined; error?: undefined }
  | { status: "error"; data?: T; error: { messageKey: string; code?: string } };

export type ActionCallbacks<T> = {
  readonly onCreate?: (draft?: Partial<T>) => void | Promise<void>;
  readonly onUpdate?: (item: T) => void | Promise<void>;
  readonly onDelete?: (item: T) => void | Promise<void>;
  readonly onRefresh?: () => void | Promise<void>;
};

export type I18nLabel = {
  readonly labelKey: string;
  readonly descriptionKey?: string;
};

export type RegistryGate = {
  readonly permission?: string;
  readonly flag?: string;
};

export type SidebarRegistryItem = I18nLabel &
  RegistryGate & {
    readonly id: string;
    readonly href: string;
    readonly icon?: string;
    readonly children?: readonly SidebarRegistryItem[];
  };

export type BreadcrumbRegistryItem = I18nLabel &
  RegistryGate & {
    readonly id: string;
    readonly href?: string;
  };

export type MobileRegistryItem = I18nLabel &
  RegistryGate & {
    readonly id: string;
    readonly href: string;
    readonly priority?: number;
  };

export type PortalRegistryItem = I18nLabel &
  RegistryGate & {
    readonly id: string;
    readonly slot: string;
    readonly order?: number;
  };

export type ShellRegistries = {
  readonly sidebar?: readonly SidebarRegistryItem[];
  readonly breadcrumbs?: readonly BreadcrumbRegistryItem[];
  readonly mobile?: readonly MobileRegistryItem[];
  readonly portals?: readonly PortalRegistryItem[];
};

// --- Subframe-Adapter contract (M015) ---
/** Swappable UI implementation: renders a serializable component model to HTML. */
export type UiRenderer<Model> = (model: Model) => string;

export type DataTableColumn = I18nLabel & { readonly key: string; readonly align?: "left" | "right" | "center" };
export type DataTableRow = { readonly id: string; readonly cells: Readonly<Record<string, string>> };
/** Domain View-Model a loader builds for a tabular list. */
export type DataTableVM = {
  readonly caption?: I18nLabel;
  readonly columns: readonly DataTableColumn[];
  readonly rows: readonly DataTableRow[];
  readonly emptyLabelKey?: string;
};
/** Normalized component prop-model the UI implementation renders. */
export type DataTableModel = {
  readonly captionKey?: string;
  readonly columns: readonly { readonly key: string; readonly labelKey: string; readonly align: "left" | "right" | "center" }[];
  readonly rows: readonly DataTableRow[];
  readonly emptyLabelKey: string;
  readonly rowCount: number;
};

export function ready<T>(data: T): VMState<T> {
  return { status: "ready", data };
}

export function empty<T>(): VMState<T> {
  return { status: "empty" };
}

export function assertI18nLabel(label: I18nLabel): I18nLabel {
  if (!/^[a-z][a-z0-9]*(?:[.-][a-z0-9]+)*$/.test(label.labelKey)) {
    throw new Error(`Registry labels must use i18n keys: ${label.labelKey}`);
  }
  if (label.descriptionKey && !/^[a-z][a-z0-9]*(?:[.-][a-z0-9]+)*$/.test(label.descriptionKey)) {
    throw new Error(`Registry descriptions must use i18n keys: ${label.descriptionKey}`);
  }
  return label;
}

// Domain View-Models (M013-Konvention: src/<domain>/*.vm.ts)
export * from "./walking-skeleton/walking-skeleton.vm.js";
export * from "./auth/session-list.vm.js";
export * from "./auth/select-tenant.vm.js";
export * from "./files/file-browser.vm.js";
export * from "./files/file-detail.vm.js";
export * from "./files/file-upload.vm.js";
export * from "./tasks/task-list.vm.js";
export * from "./tasks/task-detail.vm.js";