private static int insertAtIndex(int index, CompoundTag tag, NbtPath path, List<Tag> sources) throws CommandSyntaxException {
    var targets = path.getOrCreate(tag, ListTag::new);
    var result = 0;

    for (var target : targets) {
        if (!(target instanceof CollectionTag)) {
            throw ERROR_EXPECTED_LIST.create(target);
        }

        var success = false;
        var collection = (CollectionTag<?>) target;
        var cursor = index < 0 ? collection.size() + index + 1 : index;

        for (var source : sources) {
            try {
                if (collection.addTag(cursor, source.copy() /* Copying should be done in batches outside of the sources iteration. */)) {
                    ++cursor;
                    success = true;
                }
            } catch (IndexOutOfBoundsException e) {
                throw ERROR_INVALID_INDEX.create(cursor);
            }
        }

        result += success ? 1 : 0;
    }

    return result;
}