#include <string.h>
#include <iostream.h>
#include <fstream.h>

typedef char string[100];

struct node {
	char StockNbr[10];
	int QtyInStock;
	int ReOrderLevel;
	node* Next;
};

typedef node* ptrType;

ptrType ptrHead = NULL;
ptrType ptrTail = NULL;
ptrType ptrPre = NULL;
ptrType ptrCur = NULL;
ptrType ptrNew = NULL;

void PrintHelp() {
	cout << "H            (help)    Provides a summary of available commands\n";
	cout << "R <filename> (read)    Read the inventory from the specified file\n";
	cout << "W <filename> (write)   Write the inventory to the specified file\n";
	cout << "L            (list)    List the entire inventory in alphabetical order\n";
	cout << "I <StockNbr> (inquire) Display the inventory information for the specified item\n";
	cout << "N <StockNbr> (new)     Adds the specified item to the inventory\n";
	cout << "D <StockNbr> (delete)  Deletes the specified item from the inventory\n";
	cout << "B <StockNbr> (buy)     Adds to the quantity in stock for the specified item\n";
	cout << "S <StockNbr> (sell)    Subtract from the quantity in stock for the specified item\n";
	cout << "Q            (quit)    Exits the program\n";
}

void AddItem(string strInput) {
	ptrNew = new node;
	strcpy(ptrNew->StockNbr, strInput);
	ptrNew->QtyInStock = 0;
	cout << "Enter re-order level: ";
	cin >> ptrNew->ReOrderLevel;
	if ( ptrHead == NULL ) {
		ptrNew->Next = ptrHead;
		ptrHead = ptrNew;
	}
	else {
		for (ptrPre=NULL, ptrCur=ptrHead;
					(ptrCur!=NULL) && strcmp(strInput, ptrCur->StockNbr) > 0;
					ptrPre=ptrCur, ptrCur=ptrCur->Next
				);
		ptrNew->Next = ptrCur;
		ptrPre->Next = ptrNew;
	}
	cout << ptrNew->StockNbr << " has been added to the inventory\n";
}

void ListInventory() {
	if ( ptrHead == NULL )
		cout << "ListInventory Error: File Not Read!!\n";
	else {
		for (ptrCur=ptrHead; ptrCur!=NULL; ptrCur = ptrCur->Next) {
			cout << ptrCur->StockNbr << " " << ptrCur->QtyInStock << " " << ptrCur->ReOrderLevel << "\n";
		}
	}
}

void ItemInfo(string strInput) {
	if ( ptrHead == NULL )
		cout << "ItemInfo Error: File Not Read!!\n";
	else {
		for (ptrCur=ptrHead;
			(ptrCur!=NULL) && (strcmp(ptrCur->StockNbr, strInput)!=0);
			ptrCur = ptrCur->Next);
		if (ptrCur!=NULL)
			cout << ptrCur->StockNbr << " " << ptrCur->QtyInStock << " " << ptrCur->ReOrderLevel << "\n";
	}
}

void BuyItem(string strInput) {
	if ( ptrHead == NULL )
		cout << "BuyItem Error: File Not Read!!\n";
	else {
		for (ptrCur=ptrHead;
			(ptrCur!=NULL) && (strcmp(ptrCur->StockNbr, strInput)!=0);
			ptrCur = ptrCur->Next);
		if (ptrCur!=NULL) {
			int amtBuy = 0;
			cout << "Enter amount bought: ";
			cin >> amtBuy;
			ptrCur->QtyInStock += amtBuy;
		}
		else
			cout << strInput << " not found.\n";
	}
}

void SellItem(string strInput) {
	if ( ptrHead == NULL )
		cout << "SellItem Error: File Not Read!!\n";
	else {
		for (ptrCur=ptrHead; (ptrCur!=NULL) && (strcmp(ptrCur->StockNbr, strInput)!=0); ptrCur = ptrCur->Next);
		if (ptrCur!=NULL) {
			int amtSold = 0;
			cout << "Enter amount sold: ";
			cin >> amtSold;
			if ( amtSold > ptrCur->QtyInStock )
				cout << "Can't sell more than you have!\n";
			else
				ptrCur->QtyInStock -= amtSold;
		}
		else
			cout << strInput << " not found.\n";
	}
}

void WriteFile(string strInput) {
	if ( ptrHead == NULL )
		cout << "WriteFile Error: File Not Read!!\n";
	else {
		ofstream OutFile(strInput);
		for (ptrCur=ptrHead; ptrCur!=NULL; ptrCur = ptrCur->Next) {
			OutFile << ptrCur->StockNbr << " " << ptrCur->QtyInStock << " " << ptrCur->ReOrderLevel << "\n";
		}
		OutFile.close();
		cout << "Records written to " << strInput << "\n";
	}
}

void ReadFile(string strInput) {
	if ( ptrHead != NULL )
		cout << "ReadFile Error: File Already Read!!\n";
	else {
		ifstream InFile(strInput);
		while ( !InFile.eof() ) {
			ptrNew = new node;
			InFile >> ptrNew->StockNbr;
			InFile >> ptrNew->QtyInStock;
			InFile >> ptrNew->ReOrderLevel;
			if ( ptrNew->QtyInStock >= 0 ) {
				if ( ptrHead == NULL ) {
					ptrNew->Next = ptrHead;
					ptrHead = ptrNew;
				}
				else {
					for (ptrPre=NULL, ptrCur=ptrHead;
								(ptrCur!=NULL) && strcmp(strInput, ptrCur->StockNbr) > 0;
								ptrPre=ptrCur, ptrCur=ptrCur->Next
							);
					ptrNew->Next = ptrCur;
					ptrPre->Next = ptrNew;
				}
			}
		}
		InFile.close();
	}
}

void DelItem(string strInput) {
	if ( ptrHead == NULL )
		cout << "DelItem Error: No Inventory Items!!\n";
	else {
		for (ptrPre=NULL, ptrCur=ptrHead;
					(ptrCur!=NULL) && strcmp(strInput, ptrCur->StockNbr) > 0;
					ptrPre=ptrCur, ptrCur=ptrCur->Next
				);
		if ( strcmp(strInput, ptrCur->StockNbr) == 0 ) {
			if ( ptrPre == NULL ) {
				ptrHead = ptrHead->Next;
				ptrCur->Next = NULL;
				delete ptrCur;
				ptrCur = NULL;
			}
			else if (ptrCur->Next == NULL ) {
				ptrPre->Next = NULL;
				ptrCur->Next = NULL;
				delete ptrCur;
				ptrCur = NULL;
			}
			else {
				ptrPre->Next = ptrCur->Next;
				ptrCur->Next = NULL;
				delete ptrCur;
				ptrCur = NULL;
			}
			cout << ptrNew->StockNbr << " has been removed from the inventory\n";
		}
		else
			cout << strInput << " not found.\n";
	}
}

void main() {
	string strInput;
	string strParm;
	char *token;


	do {
		cout << "\nPlease Enter a Command: ";
		cin.getline(strInput, 100);
		if ( strlen(strInput) > 1 ) {
			token = strtok( strInput, " " );
			token = strtok( NULL, " " );
			strcpy(strParm, token);
		}
		switch ( strInput[0]) {
			case 'H': // Help: Provides a summary of available commands
			case 'h':
				PrintHelp();
				break;
			case 'N': // New: Adds the specified StockNbr to the inventory.  Prompt for ReOrderLevel.
			case 'n':
				AddItem(strParm);
				break;
			case 'L': // List: List the entire inventory in alphabetical order
			case 'l':
				ListInventory();
				break;
			case 'I': // Inquire: Display the inventory information for the specified StockNbr
			case 'i':
				ItemInfo(strParm);
				break;
			case 'B': // Buy: Adds to the quantity in stock for the specified StockNbr.  Prompt for quantity.
			case 'b':
				BuyItem(strParm);
				break;
			case 'S': // Sell: Subtract from the quantity in stock for the specified StockNbr.  Prompt for quantity.
			case 's':
				SellItem(strParm);
				break;
			case 'W': // Write: Write the inventory to the specified file
			case 'w':
				WriteFile(strParm);
				break;
			case 'R': // Read: Read the inventory from the specified file
			case 'r':
				ReadFile(strParm);
				break;
			case 'D': // Delete: Deletes the specified StockNbr from the inventory.
			case 'd':
				DelItem(strParm);
				break;
			case 'Q':
			case 'q':
				break;
			default:
				cout << "\nInvalid Command";
		}
	} while ( strInput[0] != 'Q' && strInput[0] != 'q' );
}