//-------------------------------------------------------------------
// File   :grades.C
// Author :Alicia Thorsen
// Course :CS1129 
//
// Program reads student names and numeric grades from an input file, calculates
// their letter grades and writes it all to a file.
//-------------------------------------------------------------------

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

const int MAX_STUDENTS = 100;
const int MAX_NAME_SIZE = 25;
const int MAX_NUMERIC_GRADE_SIZE = 15;

// NOTE: Cannot store filenames as strings if they are used by the file open
// function. Must use character arrays.
const char IN_FILE_NAME[] = "input.txt";
const char OUT_FILE_NAME[] = "output.txt";

int getStudentData(string [], double []);
void outputStudentData(const string [], const double [], const string [], int);
void calcLetterGrade(const double [], string [], int);

//Main Function.

int main() {
  string name[MAX_STUDENTS];
  double numericGrade[MAX_STUDENTS];
  string letterGrade[MAX_STUDENTS];
  int numStudents = 0;
  
  // Read input from file.
  numStudents = getStudentData(name, numericGrade);
  
  // Calculate letter grades from numeric grades.
  calcLetterGrade(numericGrade, letterGrade, numStudents);
  
  // Output student info with letter grades to a file.
  outputStudentData(name, numericGrade, letterGrade, numStudents);
  
  cout << endl;
  return 0;
  
} // end main().

// ------------------------------------------------------------
// Precondition :IN_FILE_NAME exists and contains student data.
// Postcondion  :Student data is stored in name[] and numericGrade[]
//              and the number of the students read is returned.
// ------------------------------------------------------------

int getStudentData(string name[], double numericGrade[]) {
  ifstream inputFile;
  string studentName;
  int i = 0;
  
  // Open file for reading.
  inputFile.open(IN_FILE_NAME);
  
  // Read first line.
  getline(inputFile, studentName);
  
  // Keep reading until end-of-file.
  while (!inputFile.eof()) {
    // First line is student name.
    name[i] = studentName;
    
    // Second line is numeric grade.
    inputFile >> numericGrade[i];
    
    // Discard newline left by >>.
    inputFile.ignore();
    
    // Read next line.
    getline(inputFile, studentName);
    
    // Keep track of entries read.
    ++i;
  }
  
  // Close file.
  inputFile.close();
  
  // Return number of students in file.
  return i;
}

// ------------------------------------------------------------
// Precondition   :numericGrade[] contains students' numeric grades.
// Postcondition  :letterGrade[] contains students' letter grades.
// ------------------------------------------------------------

void calcLetterGrade(const double numericGrade[], string letterGrade[],
                     int numStudents) {
  // Determine letter grade.
  for (int i = 0; i < numStudents; ++i)
    if (numericGrade[i] >= 89.5)
      letterGrade[i] = "A";
    else if (numericGrade[i] >= 86.5)
      letterGrade[i] = "AB";
    else if (numericGrade[i] >= 79.5)
      letterGrade[i] = "B";
    else if (numericGrade[i] >= 76.5)
      letterGrade[i] = "BC";
    else if (numericGrade[i] >= 69.5)
      letterGrade[i] = "C";
    else if (numericGrade[i] >= 66.5)
      letterGrade[i] = "CD";
    else if (numericGrade[i] >= 59.5)
      letterGrade[i] = "D";
    else
      letterGrade[i] = "F";
}

// ------------------------------------------------------------
// Precondition   :name[], numericGrade[], letterGrade[] have student data and
//                numStudents contains the size of the arrays.
// Postcondition  :All student data is written to the OUT_FILE_NAME file.
// ------------------------------------------------------------

void outputStudentData(const string name[], const double numericGrade[], 
                       const string letterGrade[], int numStudents) {
  ofstream outputFile;
  
  // Open file for writing.
  outputFile.open(OUT_FILE_NAME);
 
  // Left align columns.
  outputFile.setf(ios::left);
  
  // Write headings to file:
  outputFile << setw(MAX_NAME_SIZE) << "Name"
      << setw(MAX_NUMERIC_GRADE_SIZE) << "Numeric Grade" << "Letter Grade\n\n";
  
  // Write student data to file.
  for (int i = 0; i < numStudents; ++i) {
    outputFile << setw(MAX_NAME_SIZE) << name[i]
        << setw(MAX_NUMERIC_GRADE_SIZE) << numericGrade[i] << letterGrade[i] 
        << endl;     
  }
  // Close file.
  outputFile.close();
  
  cout << "\nResults written to " << OUT_FILE_NAME << endl;
}