/**
 * Canonical "no value" placeholder for the IMS frontend (#691).
 *
 * Missing/null/empty values must render identically everywhere. Route every
 * display fallback through {@link EMPTY} (or the {@link displayValue} helper)
 * instead of writing ad-hoc `?? "-"` / `?? "—"` literals, so the placeholder
 * stays consistent and there is a single place to change it.
 *
 * This is a *display* concept only. It does NOT apply to non-display empties
 * such as date-field form values, CSV cells, or URL query params, which
 * legitimately use an empty string.
 */
export const EMPTY = "—";

/**
 * Coerce a possibly-missing value to a display string, falling back to the
 * canonical {@link EMPTY} placeholder for:
 * - `null` / `undefined`,
 * - blank/whitespace-only strings, and
 * - non-finite numbers (`NaN`, `Infinity`) — so a missing amount renders
 *   "—" instead of a raw "NaN".
 *
 * Finite numbers and non-blank strings are returned as their string form, and
 * booleans/bigints are stringified. Objects, symbols, and functions have no
 * meaningful display string (`String({})` is "[object Object]"), so they also
 * fall back to {@link EMPTY}.
 */
export function displayValue(value: unknown): string {
  if (value == null) return EMPTY;
  if (typeof value === "number") {
    return Number.isFinite(value) ? String(value) : EMPTY;
  }
  if (typeof value === "string") {
    return value.trim() === "" ? EMPTY : value;
  }
  if (typeof value === "boolean" || typeof value === "bigint") {
    return String(value);
  }
  // Objects, symbols, and functions have no meaningful display string
  // (`String({})` is "[object Object]"), so treat them as "no value".
  return EMPTY;
}