// This program sets up a file of blank inventory records.
#include <iostream>
#include <fstream>
using namespace std;

const int DESC_SIZE = 31, NUM_RECORDS = 5;

// Declaration of Invtry structure.
struct Invtry
{
    char desc[DESC_SIZE];
    int qty;
    double price;
};

int main()
{
    // Variables needed to read and write the file.
    Invtry record = { "", 0, 0.0 };
    long recNum;

    // Create file object and open file.
    fstream inventory("invtry.dat", ios::in | ios::out | ios::binary);
    if (!inventory)
    {
        cout << "Error opening file.";
        return 0;
    }

    // Now write the blank records.
    for (int count = 0; count < NUM_RECORDS; count++)
    {
        cout << "Now writing record " << count << endl;
        inventory.write(reinterpret_cast<char *>(&record), sizeof(record));
//      inventory.write((char *)&record, sizeof(record));   //older method of type casting
    }

    // Rewind the file
    inventory.seekg(0L, ios::beg);

    // Now read and display the records
    cout << endl << "Now reading and displaying the records" << endl << endl;

    inventory.read(reinterpret_cast<char *>(&record), sizeof(record));
//  inventory.read((char *)&record, sizeof(record));        //older method of type casting
    while (!inventory.eof())
    {
        cout << "Description: ";
        cout << record.desc << endl;
        cout << "Quantity: ";
        cout << record.qty << endl;
        cout << "Price: ";
        cout << record.price << endl << endl;
        inventory.read(reinterpret_cast<char *>(&record), sizeof(record));
//      inventory.read((char *)&record, sizeof(record));    //older method of type casting
    }

    // Move to the desired record and read it into record.
    cout << "Which record do you want to edit?";
    cin >> recNum;
    inventory.seekg(recNum * sizeof(record), ios::beg);
    inventory.read(reinterpret_cast<char *>(&record), sizeof(record));
//  inventory.read((char *)&record, sizeof(record));        //older method of type casting

    // Get new data from user and edit in-memory record.
    cout << endl << "Current information" << endl;
    cout << "Description: ";
    cout << record.desc << endl;
    cout << "Quantity: ";
    cout << record.qty << endl;
    cout << "Price: ";
    cout << record.price << endl << endl;
    cout << "Enter the new data:\n";
    cout << "Description: ";
    cin.ignore();                   //skip next character in input buffer
    cin.getline(record.desc, DESC_SIZE);
    cout << "Quantity: ";
    cin >> record.qty;
    cout << "Price: ";
    cin >> record.price;

    // Move to the right place in file and write the record.
    inventory.seekp(recNum * sizeof(record), ios::beg);
    inventory.write(reinterpret_cast<char *>(&record), sizeof(record));
//  inventory.write((char *)&record, sizeof(record));       //older method of type casting

    // Move to the desired record and read the update record.
    inventory.seekg(recNum * sizeof(record), ios::beg);
    inventory.read(reinterpret_cast<char *>(&record), sizeof(record));
//  inventory.read((char *)&record, sizeof(record));        //older method of type casting

    // Get new data from user and edit in-memory record.
    cout << endl << "Updated information" << endl;
    cout << "Description: ";
    cout << record.desc << endl;
    cout << "Quantity: ";
    cout << record.qty << endl;
    cout << "Price: ";
    cout << record.price << endl << endl;

    //Close the file.
    inventory.close();

    return 0;
}