#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string.h>
using namespace std;
 
struct tstudent{		// main file
	int nr_entry;
	int student_number;
	char name[35];
	int year;
};
 
struct tindex{		// index file
	int student_number;
};
fstream dat,ind;	// file objects
 
void input(char *character_array)	// function to avoid newline
{
	cin.getline(character_array,150);
	if(cin.gcount()==1)
		cin.getline(character_array,150);
}
 
 
void manual_input(){
	tstudent layer;
	tindex index;
	int counter;
	// 1. number of file entries
	if(!dat){
		counter=0;
		dat.open("student.dat",ios::out|ios::binary);
	}
	else{ // file exists
		dat.seekg(0,ios::end);
		counter=dat.tellg()/sizeof(tstudent);
		dat.close();
		dat.open("student.dat",ios::out|ios::app|ios::binary);
		ind.open("student.ind",ios::out|ios::app|ios::binary);
	}
	// 2. adding a new entry into the file
	counter++;
	cout << "Entry number "  << counter << endl;
	layer.nr_entry=counter;
	cout << "Student's number:"; cin >> layer.student_number;
	cout << "First and last name:";input(layer.name);
	cout << "Year of college:";cin >> layer.year;
	dat.write((char *)&layer,sizeof(tstudent));
	index.student_number=layer.student_number;
 
	ind.write((char *)&index,sizeof(tindex));
	dat.close();
	ind.close();
};//manual_input() END
 
void output_entries(){
  tstudent layer;
  tindex index;
  dat.open ("student.dat",ios::in|ios::binary);
  ind.open ("student.ind",ios::in|ios::binary);
    while (1){
    ind.read ((char *)&index,sizeof(tindex));
    if (ind.eof())break;
    dat.seekg(index.student_number);
    dat.read ((char *)&layer, sizeof(tstudent));
    cout << "Entry number " << layer.nr_entry << endl;
    cout << "Student's number:" <<layer.student_number << endl;
    cout << "First and last name:"<<layer.name<<endl;
    cout << "Year of college:"<<layer.year<<endl;
  }//while
  dat.close();
  ind.close();
};//output_entries() END
 
 
void entry_search(int nr){
  tstudent layer;
  tindex index;
  bool found=false;
  int counter=0;
  dat.open ("student.dat",ios::in|ios::binary);
  ind.open ("student.ind",ios::in|ios::binary);
  while (1){
    ind.read ((char *)&index, sizeof(tindex));
    counter++;
    if (ind.eof())break;
    if (index.student_number==nr){
      dat.seekg(index.student_number);
      dat.read ((char *)&layer, sizeof(tstudent));
      found=true;
      cout << "Entry number: " << layer.nr_entry << endl;
      cout << "Student's number:"<<layer.student_number << endl;
      cout << "First and last name:"<<layer.name<<endl;
      cout << "Year of college:"<<layer.year<<endl;
      break;
    }//if
  }//while
  dat.close();
  ind.close();
  if (!found) cout << "The entry wasn't found!" << endl;
  cout <<"Number of entries read:"<<counter<<endl;
};
 
int main(){
  int choice;
  int nr;
  do{cout << endl;
    cout << "1. adding a new entry into main and index (manually)" << endl;
    cout << "2. print all the entered data" << endl;
    cout << "3. Search the entries" << endl;
    cout << "4. Exit the program" << endl;
    cin >> choice;
    switch (choice){
      case 1:manual_input();break;
      case 2:output_entries();break;
      case 3:cout << "Student's number:"; cin >> nr;
		  entry_search(nr);break;
	  case 4: exit(0);
    }//switch
  } while (choice!=9);
	return 1;
}