public IEnumerable <TEntity> GetEntitiesByParent(string parentType, string parentId, EntityLookupRoot lookupRoot)
 {
     throw new NotImplementedException();
 }
        public IEnumerable <TEntity> GetEntitiesByParent(string parentType, string parentId, EntityLookupRoot lookupRoot)
        {
            List <TEntity> cachedEntities   = new List <TEntity>();
            List <string>  missingEntityIds = new List <string>();
            var            references       = _snapshotStore.GetChildSnapshotReferences <TSnapshot>(parentType, parentId).ToList();

            if (references.Count == 0)
            {
                return(Enumerable.Empty <TEntity>());
            }

            foreach (var reference in references)
            {
                if (lookupRoot.TryGetValue(reference, out TEntity entity))
                {
                    cachedEntities.Add(entity);
                }
                else
                {
                    missingEntityIds.Add(reference.EntityID);
                }
            }

            List <TEntity> missingEntiies     = new List <TEntity>();
            var            snapshots          = _snapshotStore.GetSnapshots <TSnapshot>(missingEntityIds).ToList();
            var            subEntitySnapshots = GetSubEntitySnapshotLookup(snapshots);

            foreach (var snapshot in snapshots)
            {
                if (subEntitySnapshots == null)
                {
                    TEntity entity = LoadEntityFromSnapshot(snapshot, null);
                    entity.LookupRoot = lookupRoot;
                    lookupRoot.Add(entity);
                    missingEntiies.Add(entity);
                }
                else
                {
                    EntityReference       snapshotReference = new EntityReference(typeof(TEntity).Name, snapshot.EntityID);
                    List <EntitySnapshot> subEntities       = null;
                    if (!subEntitySnapshots.TryGetValue(snapshotReference, out subEntities))
                    {
                        subEntities = new List <EntitySnapshot>();
                    }

                    TEntity entity = LoadEntityFromSnapshot(snapshot, subEntities);
                    entity.LookupRoot = lookupRoot;
                    lookupRoot.Add(entity);
                    missingEntiies.Add(entity);
                }
            }

            return(cachedEntities.Concat(missingEntiies));
        }