namespace Jellyfin.Plugin.SmartPlaylist.Util {
    public interface IStream<T> {
        int available();
        T get();
        int commit();
        int rewind();
        int rewind(int n);
    }

    public class Stream<T> : IStream<T> {
        private readonly IList<T> _items;
        private int _cursor;
        private int _ephemeral_cursor;

        protected Stream(IList<T> items) {
            _items = items;
            _cursor = 0;
            _ephemeral_cursor = 0;
        }

        public int available() {
            return _items.Count - _ephemeral_cursor;
        }
        public T get() {
            return _items[_ephemeral_cursor++];
        }
        public int commit() {
            int diff = _ephemeral_cursor - _cursor;
            _cursor = _ephemeral_cursor;
            return diff;
        }
        public int rewind() {
            int diff = _ephemeral_cursor - _cursor;
            _ephemeral_cursor = _cursor;
            return diff;
        }
        public int rewind(int n) {
            int diff = _ephemeral_cursor - _cursor;
            if (diff < n) {
                n = diff;
            }
            _ephemeral_cursor -= n;
            return n;
        }
    }
}