import '../../models/document_model.dart';

/// Result of merging the server's document list with local corrections that
/// haven't made it back to the server yet.
class MergedDocuments {
  final List<DocumentModel> docs;
  final Set<String> unsyncedIds;

  const MergedDocuments(this.docs, this.unsyncedIds);
}

/// Merges the server's authoritative document list with local corrections for
/// documents whose `PUT` sync failed (`syncFailed` in the pending queue).
///
/// Without this, refreshing the documents list would silently overwrite a
/// driver's corrected-but-unsynced edit with the server's stale pre-edit copy
/// on every successful fetch - the correction is still recoverable via the
/// pending queue's retry action, but the history list would show the wrong
/// data (or the document would vanish from it entirely) until the retry
/// succeeds. `unsyncedOverrides` wins over `serverDocs` for matching ids, and
/// is kept even if the server list doesn't (yet) include that id at all.
MergedDocuments mergeDocumentsWithUnsyncedOverrides({
  required List<DocumentModel> serverDocs,
  required Map<String, DocumentModel> unsyncedOverrides,
}) {
  final merged = <String, DocumentModel>{
    for (final doc in serverDocs) doc.id: doc,
  };
  for (final entry in unsyncedOverrides.entries) {
    merged[entry.key] = entry.value;
  }
  return MergedDocuments(merged.values.toList(), unsyncedOverrides.keys.toSet());
}