/**
 * Pure id + keyboard helpers for the admin panel-tabs pattern (WAI-ARIA Tabs).
 *
 * Kept React-free so the id contract and the key resolver can be tested and
 * reused without mounting anything. `PanelTabs.tsx` is the only renderer.
 */

import { resolveRovingIndex } from "../../frontend/shared/rovingFocus";

export interface PanelTabDescriptor {
  id: string;
  label: string;
}

/** id of the `role="tab"` button for `tabId` within the `baseId` tablist. */
export function tabControlId(baseId: string, tabId: string): string {
  return `${baseId}-tab-${tabId}`;
}

/** id of the `role="tabpanel"` element for `tabId` within the `baseId` tablist. */
export function tabPanelId(baseId: string, tabId: string): string {
  return `${baseId}-panel-${tabId}`;
}

/**
 * Props to spread onto a panel's existing wrapper element. Panels are mounted
 * only while active, so the tab's `aria-controls` is likewise only set while
 * the panel exists — see `PanelTabs`.
 */
export function tabPanelProps(
  baseId: string,
  tabId: string,
): { role: "tabpanel"; id: string; "aria-labelledby": string } {
  return {
    role: "tabpanel",
    id: tabPanelId(baseId, tabId),
    "aria-labelledby": tabControlId(baseId, tabId),
  };
}

/**
 * Pure keyboard resolver for a horizontal tablist. Returns the tab id that
 * should become active+focused, or null for keys we do not own.
 *
 * Deliberately narrower than the radio-group resolver: a horizontal tablist
 * must NOT swallow ArrowUp/ArrowDown (the user is scrolling the panel), and
 * Enter/Space already activate the focused tab through its native click.
 * Movement wraps at both ends; horizontal arrows are RTL-aware.
 */
export function resolvePanelTabKey(
  key: string,
  currentId: string,
  tabIds: readonly string[],
  rtl = false,
): string | null {
  const count = tabIds.length;
  if (count === 0) return null;

  const targetIndex = resolveRovingIndex(
    key,
    tabIds.indexOf(currentId),
    count,
    "horizontal",
    rtl,
  );

  return targetIndex === null ? null : tabIds[targetIndex];
}