#include <iostream>
#include <fstream>
#include <string>
using namespace std;

#define N_stu 100

//declare sturcture "students"
struct students
{
	string name;//store name
	string ssn;//store ssn
	char T1,T2,T3,T4,T5;//store 5 test
}student[N_stu];

int get_file(char *filename);
int search(int n,string s,int num);
double cal(int num);
double letter_num(char);
int save_file(int,char *filename);

int main(int argc, char *argv[])
{
	//declare variables
	int num_stu=0;
	int j = 1;
	int i,c;
	string s;
	char filename[30];
	

	
	//convert file into structure arrays
	num_stu=get_file(argv[1]);
	cout<< endl << "Finish loading, find "<<num_stu<<" student records. "<<endl <<endl;


	//loop for user interface

	while(1){

		cout<< "Please enter the command :";
		getline(cin,s);

		if( s.substr(0,3) == "gpa"  || s.substr(0,3) == "GPA")
		{
			s.erase(0,4);
			i=search(0,s,num_stu);
			if (i != (N_stu+1) )
			{cout<< endl<<student[i].name <<"'s average GPA is " <<cal(i)<<endl <<endl;}else
			{cout<< s <<" is not found"<<endl<<endl;}
		}
		else if( s.substr(0,3) == "ssn"  || s.substr(0,3) == "SSN") {
			s.erase(0,4);
			i=search(0,s,num_stu);
			if (i != ( N_stu+1 ) ){
			cout<< endl<<student[i].name <<"'s SSN is " << student[i].ssn <<endl <<endl;}else
			{cout<< s <<" is not found"<<endl<<endl;}
		}
		else if( s.substr(0,6) == "update"  || s.substr(0,6) == "UPDATE") {
			s.erase(0,7);
			i=search(0,s,num_stu);
			if (i!= ( N_stu+1 ) )
			{
				while(j!=0)
				{
					cout<<"Please enter 1-5 to change " << s <<"'s test store or enter 0 to return to main menu ";
					cin>>j;
					switch(j){
					case 1: 
						cout<< "Please enter test grade(ABCDF): ";
						cin>>student[i].T1;
						break;
					case 2: 
						cout<< "Please enter test grade(ABCDF): ";
						cin>>student[i].T2;
						break;
					case 3: 
						cout<< "Please enter test grade(ABCDF): ";
						cin>>student[i].T3;
						break;
					case 4: 
						cout<< "Please enter test grade(ABCDF): ";
						cin>>student[i].T4;
						break;
					case 5: 
						cout<< "Please enter test grade(ABCDF): ";
						cin>>student[i].T5;
						break;
					case 0: 
						save_file(num_stu,argv[1]);
						getline(cin,s);break;
					}
				}
			}
			else
			{cout<< s <<" is not found"<<endl<<endl;}
		}
		else if( s.substr(0,4) == "save"  || s.substr(0,4) == "SAVE") {
			s.erase(0,5);
			for( i = 0;i <s.length();i++)
			{filename[i]=s.at(i);}
			ofstream file (filename, ios::out);
			for(i=0;i<num_stu;i++)
			{
				file << student[i].name <<" " << student[i].ssn << " " << student[i].T1 <<" "
				<< student[i].T2 << " " << student[i].T3 << " " <<student[i].T4 << " "
				<< student[i].T5 ;
				file << " \n";
			}
			cout<< "file saved..."endl<<endl;
		}
		else if( s.substr(0,4) == "quit"  || s.substr(0,4) == "QUIT") {return 0;}	
	}
	return 0;
}

int get_file(char *filename)
{
	//delcare local variables
	int n=1;
	int line = 0;
	char c;
	ifstream file;
	int j=0; //number of word read
	
	//open file
	file.open(filename);
	if ( file.fail() )
	{
		cout<< "There is no file named \"" <<filename <<"\""<<endl;
		return(0);
	}
	
	cout<< "File loading please wait ";

	//get file data
	while (file.good())
	{
		c = file.get();
		if ( ( c<=(int)'9' && c>=(int)'0')
			||( c<=(int)'Z' && c>=(int)'A')
			||( c<=(int)'z' && c>=(int)'a') 
			|| ( c==(int)'-') )
		{
			//cout<< c;
			switch(j%7)
			{
			case 0://name
				student[line].name += c;
				n=1;break;
			case 1://ssn
				student[line].ssn += c;
				n=1;break;
			case 2://grade
				student[line].T1 = c;
				n=1;break;
			case 3:
				student[line].T2 = c;
				n=1;break;
			case 4:
				student[line].T3 = c;
				n=1;break;
			case 5:
				student[line].T4 = c;
				n=1;break;
			case 6:
				student[line].T5 = c;
				n=1;line++;break;
			default:
				return(0);
			}

		}else 
		{
			switch(n)
			{
			case 1:
				j++;n=0;;break;}
		}
	}
	file.close();
	return(line);
}

int search(int n,string s,int num)
{
	int i;
	switch(n){
	case 0:
		for(i=0;i<num;i++)
		{
			if(s==student[i].name)
			return(i);
		}
		return(N_stu+1);
		break;
	case 1:
		for(i=0;i<num;i++)
		{
			if(s==student[i].ssn)
			return(i);
		}
		return(N_stu+1);
		break;
	}
	return(N_stu+1);
}

double cal(int num)
{
	double gpa= 0.0;
	gpa=( letter_num(student[num].T1)+
		letter_num(student[num].T2)+
		letter_num(student[num].T3)+
		letter_num(student[num].T4)+
		letter_num(student[num].T5) )/5;
	return (gpa);
}

double letter_num(char c)
{
	if (c == 'a' ||c == 'A')
		return(4.0);
	if (c == 'b' ||c == 'B')
		return(3.0);
	if (c == 'c' ||c == 'C')
		return(2.0);
	if (c == 'd' ||c == 'D')
		return(1.0);
	return(0.0);
}

int save_file(int num,char *filename)
{
	ofstream file (filename, ios::out);
	int i;
	for(i=0;i<num;i++)
	{
		file << student[i].name <<" " << student[i].ssn << " " << student[i].T1 <<" "
		<< student[i].T2 << " " << student[i].T3 << " " <<student[i].T4 << " "
		<< student[i].T5 ;
		file << " \n";
	}
	file.close();
	return 0;
}