//------------------------------------------------------------------
//
// A program that illustrates the use of arrays in 
// the context of the patient record example.
//
// Simon Parsons
// March 6th 2007.
//
//------------------------------------------------------------------

//------------------------------------------------------------------
//
// Link the necessary libraries

#include <iostream>
#include <fstream>

using namespace std;

//------------------------------------------------------------------
//
// Declare variables

int idNumber;
int age;
int disease;
int zipCode;

//------------------------------------------------------------------
//
// A method to print out the patient data

void printRecord()
{
  cout << "Patient ID: \t"  << idNumber << endl;
  cout << "Age: \t\t"       << age      << endl;
  cout << "ZIPcode: \t"     << zipCode  << endl;
  cout << "Suffers from: \t"<< disease  << endl;
  cout << endl;
}

//------------------------------------------------------------------
//
// The main method

int main()
{

    // Initialisation

    const int LENGTH = 7;           // The length of arrays
    int diseases[LENGTH];           // Declare two arrays to hold
    int ages[LENGTH];               // patient data
    int recordCounter;              // Declare counter
    int ageOfOldest = 0;            // Three variables to hold aggregate
    int sumOfAges =0;               // data about patients
    int numberOfDiseases = 0;       // 

    ifstream infile("patient.dat"); // Open the patient record file

    //--------------------------------------------------------------
    //
    // Read records from the file
    //
    // Since in this case we know that there are at least 7 records in
    // the file, we can use a for loop.

    for(recordCounter = 0; recordCounter < LENGTH ; recordCounter++)
    {
        infile >> idNumber;         // Read data in from
        infile >> age;              // file.
        infile >> disease;
        infile >> zipCode;

        // Store disease and age data in arrays

        diseases[recordCounter] = disease;
        ages[recordCounter]     = age;

        printRecord();              // Print data
    }

    infile.close();                 // We are done reading from the file, so
                                    // we can close it.

    //--------------------------------------------------------------
    //
    // Print out diseases in reverse order
    //
    // Since we have stored the data from the file in the arrays, we
    // can use it even though the file is now closed. We just step
    // through the array backwards printing out each member.

    cout << endl << "Diseases in reverse order" << endl << endl;

    for(recordCounter = LENGTH - 1; recordCounter >= 0;  recordCounter--)
    {
        cout << diseases[recordCounter] << endl;
    }

    //--------------------------------------------------------------
    //
    // Find the oldest patient
    //
    // To find the oldest patient, we go through the array entry by
    // entry, looking to see if the number that is the latest entry is
    // bigger than all the previous biggest.

    cout << endl << "The oldest patient is: ";

    for(recordCounter = LENGTH - 1; recordCounter >= 0;  recordCounter--)
    {
        if(ages[recordCounter] > ageOfOldest)
	  {
	    ageOfOldest = ages[recordCounter];
	  }
    }

    cout << ageOfOldest << endl;
    
    //--------------------------------------------------------------
    //
    // Compute average age of patients
    // 
    // To calculate the average age, we first need to add up the ages
    // of all the patients. We do this by adding each member of the
    // array to a running total.

    for(recordCounter = 0; recordCounter < LENGTH;  recordCounter++)
    {
      sumOfAges += ages[recordCounter];  // Add each age in turn to
    }                                    // the running total.

    // Set the number of decimal places of the output

    cout.setf(ios::fixed, ios::floatfield);
    cout.precision(1);

    // Calculate the average age and print it

    cout << "Average age is: ";
    cout << sumOfAges / (LENGTH * 1.0) << endl;

    //--------------------------------------------------------------
    //
    // Count the number of cases of a given disease.
    // 
    // Ask  the user for a disease. Then look through the array, and increase 
    // the count each time we find an instance of this disease.

    // Get disease number from user

    cout << endl << "Enter disease: ";
    cin  >> disease;

    // Count the number of times we see that disease

    for(recordCounter = 0; recordCounter < LENGTH;  recordCounter++)
    {
      if(diseases[recordCounter] == disease)  // If the disease in the 
	{                                     // array matches the one we
	  numberOfDiseases += 1;              // are looking for, increase 
	}                                     // the count.
    }

    // Print out the number of times we found the disease

    cout << endl << "Number of patients with ";
    cout << disease << " is " << numberOfDiseases << endl << endl;

    //--------------------------------------------------------------
    //
    // End.
    
    // Note that we closed the file way back

    return 0;
}