using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public class File
    {
        FileStream fs = null;

        private StreamReader sr = null;
        private StreamWriter sw = null;

        private int recsize;
        private long filesize;
        private char mode;
        private string filepath;

        public File()
        {
        }

        public long RecNum
        {
            get
            {
                return filesize / recsize;
            }
        }

        private bool checkfile(string _filepath)
        {
            int fileindex = _filepath.LastIndexOf("\\", _filepath.Length);
            string file = _filepath.Substring(fileindex + 1);

            string directorypath = _filepath.Substring(0, fileindex + 1);
            filepath = _filepath;

            if (Directory.Exists(directorypath))
            {
                string[] filenames = Directory.GetFiles(directorypath);
                foreach (string s in filenames)
                    if (s.Substring(fileindex + 1) == file) return true;
                MessageBox.Show("New file is created");
                return true;
            }
            else
            {
                MessageBox.Show("Directory doesn't exist");
                return false;
            }
        }

        public bool open(string _filepath, char _mode, int _recsize)
        {
            mode = _mode;
            recsize = _recsize;

            if (checkfile(_filepath))
            {
                switch (mode)
                {
                    case 'C':
                        fs = new FileStream(_filepath, FileMode.Create, FileAccess.ReadWrite);
                        break;
                    case 'R':
                        fs = new FileStream(_filepath, FileMode.OpenOrCreate, FileAccess.Read);
                        break;
                    case 'W':
                        fs = new FileStream(_filepath, FileMode.OpenOrCreate, FileAccess.Write);
                        break;
                    default:
                        MessageBox.Show("Error: File Access Mode(W or R)");
                        return false;
                }
                filesize = fs.Length;

                try
                {
                    switch (mode)
                    {
                        case 'R':
                            sr = new StreamReader(fs);
                            break;
                        case 'W':
                            sw = new StreamWriter(fs);
                            break;
                    }
                }
                catch (Exception Ex)
                {
                    MessageBox.Show(Ex.Message);
                    return false;
                }
                return true;
            }
            return false;
        }

        public string read(int _recordnum)
        {
            if (mode == 'R')
            {
                if ((filesize / recsize) >= _recordnum)
                {
                    int startP = _recordnum * recsize;
                    fs.Position = startP;
                    return sr.ReadLine();
                }
                MessageBox.Show("Error:Record index out of bound!");

            }
            else MessageBox.Show("Error:Record index out of writing");
            return null;
        }

        public void delete()
        {
            this.Close();
            FileStream fi = new FileStream(filepath, FileMode.Create, FileAccess.ReadWrite);
            fi.Close();
        }
        public void write(string _data)
        {
            if (mode == 'W')
                sw.WriteLine(_data);
            else MessageBox.Show("Error:File is opened for reading!");

        }
        public void Close()
        {
            switch(mode)
            {
                case 'R':
                    sr.Close();
                    break;
                case 'W':
                    sw.Close();
                    break;
            }
            fs.Close();
        }
    }
}