/* Sifter v1.0
 *
 * Author: mc0
 *
 * About: This program is used to retrive strings of information from text files using regex and
 *        regex groups.
 *
 * Usage: fileparse -l input.txt -o output.txt -v -e regex-expression -d output-expression (USE THE SAME GROUPS)
 *
 */

using System;
using System.Collections;
using System.Text;
using System.Text.RegularExpressions;
using System.IO;
using System.Threading;
using System.Web;

namespace fileParse
{
    class Program
    {
        private ArrayList sGroups;
        private string fList, fOut, sExp, sDef;
        private bool verbose;

        static void Main(string[] args)
        {
            Program p = new Program(args);
        }

        public Program(string[] args)
        {
            if (readArgs(args) == false)
            {
                usage();
                return;
            }

            ThreadStart tstart = new ThreadStart(sifter);
            Thread thread = new Thread(tstart);

            thread.Start();
        }

        private void sifter()
        {
            sGroups = findGroups(sExp);

            Regex rIn = new Regex(sExp);
            MatchCollection mData;

            StreamReader reader = new StreamReader(fList);
            try
            {
                do
                {
                    mData = rIn.Matches(reader.ReadLine());
                    foreach (Match mData1 in mData)
                    {
                        writeOutput(mData1);
                    }
                }
                while (reader.Peek() >= 0);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            finally
            {
                reader.Close();
            }
        }

        private void writeOutput(Match mData)
        {
            ArrayList sGroups = findGroups(sDef);
            string output = sDef;

            for(int i = 0;i < sGroups.Count;i++)
            {
                output = output.Replace("<" + sGroups[i].ToString() + ">", mData.Groups[sGroups[i].ToString()].Value);
            }

            output = HttpUtility.UrlDecode(output);

            StreamWriter writer = File.AppendText(fOut);
            try
            {
                writer.WriteLine(output);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            finally
            {
                writer.Close();
            }

            if (verbose)
            {
                Console.WriteLine(output);
            }
        }

        private ArrayList findGroups(string sExp)
        {
            int i = 0;
            ArrayList sGroups = new ArrayList();
            Regex rGroup = new Regex(@"<[^>]*?>");
            MatchCollection m = rGroup.Matches(sExp);

            foreach (Match match in m)
            {
                sGroups.Add(match.ToString().Substring(1, match.ToString().Length - 2));
                i++;
            }

            return sGroups;
        }

        private bool readArgs(string[] args)
        {
            for (int i = 0; i < args.Length; i++)
            {
                try
                {
                    switch (args[i])
                    {
                        case "-l":
                            fList = args[i + 1];
                            break;
                        case "-o":
                            fOut = args[i + 1];
                            break;
                        case "-v":
                            verbose = true;
                            break;
                        case "-e":
                            sExp = args[i + 1];
                            break;
                        case "-d":
                            sDef = args[i + 1];
                            break;
                    }
                }
                catch
                {
                    return false;
                }
            }

            if(String.IsNullOrEmpty(fList) ||
                String.IsNullOrEmpty(fOut) ||
                String.IsNullOrEmpty(sExp))
            {
                return false;
            }

            return true;
        }

        private void usage()
        {
            Console.WriteLine("Sifter v1.0");
            Console.WriteLine("Usage: \n");
           Console.WriteLine("  -l <FileName> REQUIRED");
            Console.WriteLine("      Specify the name of the file containing the");
            Console.WriteLine("      information you wish to have parsed here.\n");
            Console.WriteLine("  -o <FileName> REQUIRED");
            Console.WriteLine("      Specify the name of the file you wish to have ");
            Console.WriteLine("      your parsed information written to here.\n");
            Console.WriteLine("  -v");
            Console.WriteLine("      Verbose option.\n");
            Console.WriteLine("  -e <String> REQUIRED");
            Console.WriteLine("      Specify the expression you wish to search for ");
            Console.WriteLine("      here (Learn how to use regex & regex groups!).\n");
            Console.WriteLine("  -d <String> REQUIRED");
            Console.WriteLine("      Specify the output string expression ");
            Console.WriteLine("      here (Learn how to use regex & regex groups!).\n");
        }
    }
}