using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;

namespace LASRead.LASFormat
{
    public class RecordCollection : IEnumerable<Record>
    {
        RecordEnumerator enumerator;
        public RecordCollection(ref Stream source, ulong startPosition, uint maxItems, IRecordPayloadHeader firstHeader)
        {
            enumerator = new RecordEnumerator(ref source, startPosition, maxItems, firstHeader);
        }
        public IEnumerator<Record> GetEnumerator()
        {
            return enumerator;
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return enumerator;
        }

    }
    public class RecordEnumerator : IEnumerator<Record>
    {
        Stream dataSource;
        ulong streamStart;
        ulong currentPosition;
        uint currentCount;
        uint maxCount;

        public RecordEnumerator(ref Stream source, ulong startPosition, uint maxItems, IRecordPayloadHeader firstHeader)
        {
            dataSource = source;
            streamStart = startPosition;
            currentPosition = startPosition;
            currentCount = 0;
            maxCount = maxItems;
            Current = new Record(firstHeader, (long)startPosition);
        }

        object IEnumerator.Current => Current;

        public Record Current { get; private set; }

        public void Dispose()
        {
            dataSource = null;
            streamStart = 0;
            currentPosition = 0;
            currentCount = 0;
            maxCount = 0;
        }

        public bool MoveNext()
        {
            if (currentCount >= maxCount)
            {
                return false;
            }
            else
            {
                long oldPos = dataSource.Position;
                currentPosition = (ulong)Current.header.HeaderLength + currentPosition;
                dataSource.Position = (long)currentPosition;
                Record nextRecord = new Record(Current.header.ParseRecord(dataSource), (long)currentPosition);
                Current = nextRecord;
                dataSource.Position = oldPos;
                currentCount++;
                return true;
            }
        }

        public void Reset()
        {
            throw new NotImplementedException();
        }
    }
}