Collect and Compare Log Statistics using LogJoin

/*
 * Copyright (c) 2013, Yuriy Nelipovich
 * 
 * If you find this code useful or in case of any questions, suggestions
 * bug reports, donation, please email me: dev.yuriy.n@gmail.com
 */

using System;
using System.IO;
using System.Linq;

namespace LogJoin
{
    /// <summary>
    /// Sequence of text portions, each portion is a line.
    /// </summary>
    public class Input : IDisposable
    {
        private readonly StreamReader[] _readers;
        private readonly FileStream[] _streams;
        private int _lastSourceIndex;

        /// <summary>
        /// Contstructs new input
        /// </summary>
        /// <param name="filePaths">Sequence of files to read</param>
        public Input(string[] filePaths)
        {
            if (filePaths.Length == 0)
                throw new ArgumentException("Empty file list");
            this._streams =
                filePaths.Select(p => new FileStream(p, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)).ToArray();
            this._readers = this._streams.Select(s => new StreamReader(s)).ToArray();
        }

        public void Dispose()
        {
            foreach (var r in this._readers)
            {
                r.Dispose();
            }
            foreach (var s in this._streams)
            {
                s.Dispose();
            }
        }

        /// <summary>
        /// Moves the input to the start position
        /// </summary>
        public virtual void ResetPosition()
        {
            this._lastSourceIndex = 0;
            foreach (var stream in this._streams.Where(stream => stream.CanSeek))
            {
                stream.Seek(0, SeekOrigin.Begin);
            }
        }

        /// <summary>
        /// Rads the next text portion and moves to the next position
        /// </summary>
        /// <returns>The text portion of null if there is nothing to read</returns>
        public virtual string ReadTextPortion()
        {
            var line = this._readers[this._lastSourceIndex].ReadLine();
            if (line != null)
                return line;

            if (this._lastSourceIndex < this._readers.Length - 1)
            {
                this._lastSourceIndex++;
                return this.ReadTextPortion();
            }
            return null;
        }
    }
}