// Begin of File

//************************************************
// Programmer : Mohammad Rastkar
// Last Build : AUG_19_08 (87\1\23)
// Compiler   : VC++2005 - Win32 Console App
// Purpose    : Separate utility to manipulate a 'Class_List' file (add, delete, modify, list Records)
//				for using later, with 'Lettered_Numbers' program
//************************************************

/////////////<	Includes    >/////////////

#include <conio.h> // getch()
#include <fstream>
#include <string>
#include <cerrno> // errno
#include <iostream>
using namespace std;

//////////////<  Variables   >//////////////

char    choice; // for choosing from menu
fstream *fs; // file stream for 'Class_List' file
string  file_str; // string as 'Class_List' file


/////////////<	Main    >/////////////

int main()
{
	fs = new fstream( "Class_List.txt", ios::in );
	
	if ( fs->bad() )
	{
		cout << "\n Can't open or create 'Class_List' file" << endl;
		system ( "pause" );
		return 1;
	}
	
	(*fs) >> file_str; // store whole of the file in 'file_str'

	fs->close();
	delete fs;
	fs=0;

	while (1)
	{
		do  // menu
		{
			system( "cls" ); // clear screen
				
			cout << "\n    < Class List > \n\n";
			cout << "(1) Add     a new student \n";
			cout << "(2) Modify  an existing student's information\n";
			cout << "(3) Delete  an existing student \n";
			cout << "(4) Display students' informations \n";
			cout << "(5) Exit \n\n";
			cout << " Enter a choice (1-5) : " << flush;
			choice = getch();

		} while ( choice < '1' || choice > '5');

		system( "cls" );

		switch ( choice )
		{
			size_t del_num; // number of characters for deletion
			size_t pos;  // a position in the string
			int rows; // on Displaying, for each 25 rows in the screen there is a pause

		
		case '1' : // Add Student
			{

				string input; // ID of student
				cout << "\n\t\t < Entering a new student > ";
				cout << "\n   Enter the following informations for the new student : ";
				
				cout << "\n\n ID : ";
				cin  >> input;

				file_str += input + '>'; // '>' -> delimiting students' informations

				cout << "\n Name (Only one word) : "; // can be more than one word
				cin  >> input;
				
				file_str += input + '>';

				cout << "\n Student was added." << endl;
				system ( "pause" );
				
				break;
			}

		case '2' : // Modify Student
			{

				string input;
				cout << "\n Enter Student ID, that you want modify its informatin : ";
				cin  >> input;

				pos = file_str.find(input);

				if (pos == string::npos) 
				{
					cout << "\n Your specified student doesn't exist in the list" << endl;
					system ( "pause" );
					break;
				}

				cout << "\nEnter new informations for this student : ";

				cout << "\n\n ID : ";
				cin  >> input;

				del_num = file_str.find('>', pos+1)-pos; // ID : first character of ID to first '>' 
				
				file_str.replace (pos, del_num, input); // replace the current ID with the new one

				
				cout << "\n Name (Only one word) : ";
				cin  >> input;
				
				pos = file_str.find('>', pos+1) + 1; // first character of Name
				del_num = file_str.find('>', pos+1)-pos; // Name : first character after first '>' to second '>'

				file_str.replace (pos, del_num, input); // replace the current Name with the new one

				cout << "\n Record was modified." << endl;
				system ( "pause" );

				break;
			}


		case '3' : // Delete Record
			{
				string input;
				cout << "\n Enter student ID, for deletion : ";
				cin  >> input;

				pos = file_str.find(input);

				if (pos == string::npos) 
				{
					cout << "\n Your specified student doesn't exist in the list" << endl;
					system ( "pause" );
					break;
				}

				file_str.erase ( file_str.begin()+pos, file_str.begin()+file_str.find('>', file_str.find('>', pos+1)+1)+1 );
				
				cout << "\n Student was deleted." << endl;
				
				system ( "pause" );

				break;
			}

		case '4' : // Display Students' Informations
			{
				cout << "ID\t\tName\n"
					 << "-----------------------------------\n";
				
				rows = 3; // 2 rows for header, and 1 for pause message at end
				
				
				pos = 0;
				string substr;  // substring for Displaying students' informations

				while (pos != file_str.length())
				{

					substr = file_str.substr( pos, file_str.find('>', pos+1)-pos );

					pos = file_str.find('>', pos+1) + 1;
					
					cout << substr;

					substr = file_str.substr( pos, file_str.find('>', pos+1)-pos );

					pos = file_str.find('>', pos+1) + 1;
					
					cout << "\t\t" << substr << endl;

					if (++rows == 25)
					{
						rows = 3;
						system ( "pause" );
						system ( "cls" );
						cout << "ID\t\tName\n"
							 << "-----------------------------------\n";
					}
				}

				cout << "End of the list." << endl;
				system ( "pause" );

				break;
			}
		case '5' : // Exit
			{
				cout << "\n Updating 'Class_List' file..." << flush;

				fs = new fstream( "Class_List.txt", ios::out );

				if (fs->fail())
				{
					cout << "\n Can't create or open 'Class_List' file, then it won't be updated." << endl;
					system ( "pause" );

					system( "cls" );
					return 1;
				}

				(*fs) << file_str;

				fs->close();
				delete fs;
				fs=0;

				if (file_str.empty()) // if we have no records, just remove the file
					remove( "Class_List.txt" );

				cout << "\n Updating completed. \n" << endl;
				
				system ( "pause" );
				system ( "cls" );

				return 0;

				break;
			}
		}
	}

	return 0;
}

// End of File