using LASRead.LASFormat;
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Reflection;

namespace LASRead.LASFormat
{
    public class PDRCollection<T> : IEnumerable where T : IPointDataRecord
    {
        readonly PDREnumerator<T> enumerator;
        public PDRCollection(FileHeader fileHeader, Stream baseStream, IPointDataRecord initialRecord)
        {
            enumerator = new PDREnumerator<T>(fileHeader, baseStream, initialRecord);
        }
        public PDREnumerator<T> GetEnumerator()
        {
            return enumerator;
        }

        public string TEst()
        {
            return "sted";
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return enumerator;
        }
    }
    /// <summary>
    /// Enumerates through the points in a .las file
    /// </summary>
    public class PDREnumerator<T>: IEnumerator<T> where T : IPointDataRecord
    {
        readonly FileHeader baseHeader;
        readonly Stream baseStream;
        // readonly int headerSize;
        //ulong endOfData;
        ushort dataLength;

        public PDREnumerator(FileHeader fileHeader, Stream baseStream, IPointDataRecord initialRecord)
        {
            Position = 0;
            baseHeader = fileHeader;
            this.baseStream = baseStream;
            //endOfData = (fileHeader.StartOfFirstExtendedVLR == 0 ? (ulong)baseStream.Length : fileHeader.StartOfFirstExtendedVLR);
            Current = (T)initialRecord;
            dataLength = fileHeader.PointDataRecordLength;

        }
        // Stream which the data is sourced from
        

        // Current payload

        /// <summary>
        /// Gets the type of the payload
        /// </summary>
        /// <returns></returns>
        public Type GetPDRFormat()
        {
            return Current.GetType();
        }

        public int EstimateRemainder()
        {
            return (int)((baseStream.Length - Position) / baseHeader.PointDataRecordLength);
        }

        object IEnumerator.Current => Current;

        public T Current { get; private set; }

        public long Position { get; private set; }


        public bool MoveNext()
        {
            if (Position + dataLength >= baseStream.Length)
            {
                return false;
            }
            else
            {
                long lastPos = baseStream.Position;
                if (baseStream.Position != Position)
                {
                    baseStream.Position = Position;
                }
                Position += dataLength;
                IPointDataRecord newRecord = (IPointDataRecord)Activator.CreateInstance(Current.GetType());
                byte[] nextData = new byte[dataLength];
                baseStream.Position = Position;
                baseStream.Read(nextData, 0, dataLength);
                bool result = newRecord.ReadPoint(nextData);
                Current = (T)newRecord;
                baseStream.Position = lastPos;
                return result;
            }
        }

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

        public void Dispose()
        {
            //throw new NotImplementedException();
        }
    }
}