https://pressthink.org/j/rosen-archive/frontend/utils/modalNav.js?v=3.8.36

1/**
2 * Prev/next navigation flags for the record modal (#421).
3 *
4 * The modal's prev/next buttons derive from the record's position in the
5 * filtered list. A deep link (?record=ID) opens the modal by looking the id up
6 * in the full records set, so a filtered-out record can still be open -- and
7 * then its index in `filteredRecords` is -1. The old inline derivation computed
8 * `hasNext = index < filteredRecords.length - 1`, which is true for index === -1
9 * whenever the list is non-empty: the Next button rendered enabled but
10 * handleModalNav no-ops on index === -1, so it looked clickable and did nothing.
11 *
12 * A record outside the filtered list has no neighbours in that list, so both
13 * flags are false. Guarding hasNext with `index >= 0` makes the button state
14 * honest (disabled) instead of inert.
15 */
16
17/**
18 * Derive the modal's position and prev/next availability.
19 * @param {Array} filteredRecords - the currently filtered record list
20 * @param {string|null} selectedRecordId - the open record's id
21 * @returns {{index: number, total: number, hasPrev: boolean, hasNext: boolean}}
22 */
23export function deriveNavFlags(filteredRecords, selectedRecordId) {
24  const list = Array.isArray(filteredRecords) ? filteredRecords : [];
25  const index = list.findIndex(r => r.id === selectedRecordId);
26  return {
27    index,
28    total: list.length,
29    hasPrev: index > 0,
30    hasNext: index >= 0 && index < list.length - 1,
31  };
32}
33
34export default { deriveNavFlags };