Jyotisha/frontend/src/lib/sidebar-state.ts

export type SidebarViewport = "mobile" | "tablet" | "desktop";

type EditableTarget = {
  readonly tagName?: unknown;
  readonly isContentEditable?: unknown;
};

export type SidebarShortcutEvent = Pick<
  KeyboardEvent,
  "key" | "metaKey" | "ctrlKey" | "altKey" | "shiftKey"
> & {
  readonly target: EventTarget | EditableTarget | null;
};

function isEditableTarget(target: SidebarShortcutEvent["target"]): target is EditableTarget {
  return target !== null && typeof target === "object";
}

export function sidebarViewportForWidth(width: number): SidebarViewport {
  if (width < 768) return "mobile";
  if (width < 1024) return "tablet";
  return "desktop";
}

export function defaultSidebarOpen(viewport: SidebarViewport): boolean {
  return viewport === "desktop";
}

export function shouldHandleSidebarShortcut(event: SidebarShortcutEvent): boolean {
  const target = event.target;
  const editable = isEditableTarget(target)
    && (target.isContentEditable === true || /^(INPUT|TEXTAREA|SELECT)$/.test(String(target.tagName ?? "")));

  return !editable
    && event.key.toLowerCase() === "b"
    && (event.metaKey || event.ctrlKey)
    && !event.altKey
    && !event.shiftKey;
}

/**
 * Where the desktop/tablet collapse state is remembered across pages.
 *
 * localStorage, not the shadcn `sidebar_state` cookie: `/` is a `○ Static`
 * route and `/chart` and `/ephemeris` are static too, so reading a cookie on
 * the server would opt all three out of static rendering. A cookie that only
 * the client may read buys nothing a localStorage key does not, so this is the
 * cheaper half of the D5 choice. The mobile drawer is deliberately excluded:
 * reopening a phone drawer on every navigation is not a preference anyone set.
 */
export const SIDEBAR_STATE_STORAGE_KEY = "sidebar_state";

type SidebarStateStorage = Pick<Storage, "getItem" | "setItem">;

function sidebarStateStorage(): SidebarStateStorage | null {
  try {
    return globalThis.localStorage ?? null;
  } catch {
    /* Private mode and blocked site data both throw on access. */
    return null;
  }
}

/** `null` when nothing was stored, or when storage is unavailable. */
export function readStoredSidebarOpen(
  viewport: SidebarViewport,
  storage: SidebarStateStorage | null = sidebarStateStorage(),
): boolean | null {
  if (viewport === "mobile" || storage === null) return null;
  try {
    const raw = storage.getItem(SIDEBAR_STATE_STORAGE_KEY);
    if (raw === "true") return true;
    if (raw === "false") return false;
    return null;
  } catch {
    return null;
  }
}

export function writeStoredSidebarOpen(
  viewport: SidebarViewport,
  open: boolean,
  storage: SidebarStateStorage | null = sidebarStateStorage(),
): void {
  if (viewport === "mobile" || storage === null) return;
  try {
    storage.setItem(SIDEBAR_STATE_STORAGE_KEY, open ? "true" : "false");
  } catch {
    /* Quota and private mode: the sidebar still works, it just forgets. */
  }
}