migrate static method

Future<void> migrate({ required String fromKey, required String toKey, String? home, int maxEntries = 1000, })

Copies the history recorded under fromKey into toKey, placing the migrated entries before any already present under toKey (consecutive duplicates are collapsed at the splice boundary). The fromKey file is left intact as a backup. A no-op when the source is missing or empty.

Used when a node's UID changes: the caller migrates the prior UID's history into the new UID's history after the user opts in.

Implementation

static Future<void> migrate({
  required String fromKey,
  required String toKey,
  String? home,
  int maxEntries = 1000,
}) async {
  final from = await load(key: fromKey, home: home, maxEntries: maxEntries);
  if (from.entries.isEmpty) return;
  final to = await load(key: toKey, home: home, maxEntries: maxEntries);
  to._entries.insertAll(0, from.entries);
  // Collapse a duplicate straddling the splice (old tail == new head).
  final boundary = from.entries.length;
  if (boundary > 0 &&
      boundary < to._entries.length &&
      to._entries[boundary - 1] == to._entries[boundary]) {
    to._entries.removeAt(boundary);
  }
  if (to._entries.length > maxEntries) {
    to._entries.removeRange(0, to._entries.length - maxEntries);
  }
  await to._persist();
}