/*
Chapter 12 HOMEWORK
Dung Tran
CS 116 C++ programming
Chapter 12 Programming Exercise #11 Inventory Program
Requirements:
	Write a program that uses a structure to store these datas in a file:
		- item Description
		- Quantity on hand
		- wholesale cost
		- retail cost
	The program should have a menu that allows the usess to perform the following tasks:
		- add new records to the file
		- display any record in the file
		- change any record in the file
*/
#include <iostream>
#include <fstream>
using namespace std;
 
// Declaration of InventoryItem structure
struct InventoryItem
{
	char desc[51];		//item description
	int qty;			//quantity on hand
	float wholesale;	//wholesale price
	float retail;		//retail price
};
 
//Function Prototypes
int menu();
void AddRecord(fstream &);
void DisplayRecord(fstream &);
void ChangeRecord(fstream &);
 
int main()
{
	int choice;
	fstream inventory ("Inventory.dat", ios::out | ios::binary);
	InventoryItem record = {" ", 0, 0.0};
 
	//writing the blank records
	for (int count = 0; count < 5; count++)
	{
		inventory.write(reinterpret_cast<char *>(&record), sizeof(record));
	}
 
	//inventory.read(reinterpret_cast<char *>(&record), sizeof(record));
 
	inventory.close();
 
	inventory.open("Inventory.dat", ios::out | ios::binary);
 
	do
	{
		choice = menu();
		switch (choice)
		{
		case 1: AddRecord(inventory);
			break;
		case 2: DisplayRecord(inventory);
			break;
		case 3: ChangeRecord(inventory);
			break;
		case 4: cout << "Exiting Program...\n\n";
		}
	}while (choice != 4);
 
	inventory.close();
	return 0;
 
}	
 
int menu ()
{
	int selection;
 
	cout << "What would you like to do?\n";
	cout << "1) add a new record to the file\n";
	cout << "2) view a record in the file\n";
	cout << "3) change a record in the file\n";
	cout << "4) Exit Program\n\b";
	cout << "Please enter 1, 2, 3, or 4: ";
	cin >> selection;
 
	while (selection< 1 || selection > 4)
	{
		cout << "Invalid Choice!!\n";
		cin >> selection;
	}
	return selection;
}
 
void ChangeRecord(fstream &file)
{
	fstream inventory ("Inventory.dat", ios::out | ios::binary);
	InventoryItem record;
	long recNum;
 
	// Get the record number of the desired record.
	cout << "Which record do you want to edit? ";
	cin >> recNum;
 
	// Move to the record and read it.
	inventory.seekg(recNum * sizeof(record), ios::beg);
	inventory.read(reinterpret_cast<char *>(&record),
		           sizeof(record));
 
	// Display the record contents
	cout << "Description: ";
	cout << record.desc << endl;
	cout << "Quantity: ";
	cout << record.qty << endl;
	cout << "Wholesale Price: ";
	cout << record.wholesale << endl;
	cout << "Retail Price: ";
	cout << record.retail << endl;
 
	// Get the new record data.
	cout << "Enter the new data:\n";
	cout << "Description: ";
	cin.ignore();
	cin.getline(record.desc, 31);
	cout << "Quantity: ";
	cin >> record.qty;
	cout << "Wholesale Price: ";
	cin >> record.wholesale;
	cout << "Retail Price: ";
	cin >> record.retail;
 
	// Move back to the beginning of this record's position.
	inventory.seekp(recNum * sizeof(record), ios::beg);
 
	// Write the new record over the current record.
	inventory.write(reinterpret_cast<char *>(&record),
		            sizeof(record));
 
	// Close the file.
	inventory.close();
}
 
void DisplayRecord(fstream &file)
{
	fstream inventory ("Inventory.dat", ios::out | ios::binary);
	InventoryItem record;
	long recNum;
 
	// Get the record number of the desired record.
	cout << "Which record would you like to open? ";
	cin >> recNum;
 
	// Move to the record and read it.
	inventory.seekg(recNum * sizeof(record), ios::beg);
	inventory.read(reinterpret_cast<char *>(&record),
		           sizeof(record));
 
	// Display the record contents
	cout << "Description: ";
	cout << record.desc << endl;
	cout << "Quantity: ";
	cout << record.qty << endl;
	cout << "Wholesale Price: ";
	cout << record.wholesale << endl;
	cout << "Retail Price: ";
	cout << record.retail << endl;
 
	//clear any error state
	if (file.fail())
		file.clear();
 
	//closing the file
	file.close();
}
 
void AddRecord(fstream &file)
{
	cout << "Please enter the information for the new data: \n";
 
	fstream inventory ("Inventory.dat", ios::out | ios::binary);
	InventoryItem record;
 
	//Info of the new data
	cout << "Description: ";
	cin.ignore();
	cin.getline(record.desc, 31);
	cout << "Quantity: ";
	cin >> record.qty;
	cout << "Wholesale Price: ";
	cin >> record.wholesale;
	cout << "Retail Price: ";
	cin >> record.retail;
 
	inventory.write(reinterpret_cast<char *>(&record),
		            sizeof(record));
 
	//closing the file
	file.close();
}