namespace Jellyfin.Plugin.SmartPlaylist.Util {
    public interface IStream<T> {
        int Available();
        T Get();
        int Commit();
        int Rewind();
        int Rewind(int n);
        int Consumed();
        IStream<T> Copy();
    }

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

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

        private Stream(IList<T> items, int cursor, int ephemeralCursor) {
            _items = items;
            _cursor = cursor;
            _ephemeralCursor = ephemeralCursor;
        }

        public int Available() {
            return _items.Count - _ephemeralCursor;
        }
        public T Get() {
            return _items[_ephemeralCursor++];
        }
        public int Commit() {
            int diff = Consumed();
            _cursor = _ephemeralCursor;
            return diff;
        }
        public int Rewind() {
            int diff = Consumed();
            _ephemeralCursor = _cursor;
            return diff;
        }
        public int Rewind(int n) {
            int diff = Consumed();
            if (diff < n) {
                n = diff;
            }
            _ephemeralCursor -= n;
            return n;
        }
        public int Consumed() {
            return _ephemeralCursor - _cursor;
        }
        public IStream<T> Copy() {
            return new Stream<T>(_items, _cursor, _ephemeralCursor);
        }
    }
}