import { isDeepStrictEqual } from 'node:util';

// Use row IDs so insertion/reordering does not masquerade as changed records.
export function jsonChanges(before, after, location = '$') {
  if (isDeepStrictEqual(before, after)) return [];
  if (Array.isArray(before) && Array.isArray(after)) {
    const keyed = rows => rows.every(row => row && typeof row === 'object' && (row.id ?? row.data?.id) != null)
      && new Set(rows.map(row => row.id ?? row.data.id)).size === rows.length;
    if (keyed(before) && keyed(after)) {
      const index = rows => Object.fromEntries(rows.map(row => [row.id ?? row.data.id, row]));
      return jsonChanges(index(before), index(after), location);
    }
  }
  if (before && after && typeof before === 'object' && typeof after === 'object'
      && !Array.isArray(before) && !Array.isArray(after)) {
    return [...new Set([...Object.keys(before), ...Object.keys(after)])].flatMap(key =>
      jsonChanges(before[key], after[key], `${location}[${JSON.stringify(key)}]`));
  }
  return [{ path: location, type: before === undefined ? 'added' : after === undefined ? 'deleted' : 'modified',
    ...(before === undefined ? {} : { before }), ...(after === undefined ? {} : { after }) }];
}