/***********************************
** Author: Steven Scott
** Filename: pex4.cpp
** Date: Oct 22, 2007
** Purpose: Keep track of inventory
** levels for a company.
***********************************/
#include <iostream>
#include <iomanip>
using namespace std;

const int maxWidgets = 500;
const int minWarning = static_cast<int>(maxWidgets * 0.1);

// Define functions
void drawMenu();
bool getCmd(int &widgets, int &accepted, int &returned,
           int &sent, int &maxpending, int &pending);
void listInv(int widgets);
void recvShip(int &accepted, int &pending, int &sent,
             int &widgets, int &returned);
void request(int &pending, int &sent, int &widgets, int &maxpending);
void cmdLoop(int widgets);
void quit(int accepted, int returned, int sent,
         int maxpending, int widgets);
int getPosInt(string q);

int main() {
 // Initialize variables with 0 values.
 int widgets = 0;
 int accepted = 0;
 int returned = 0;
 int sent = 0;
 int maxpending = 0;
 int pending = 0;
 // Draw the help menu
 drawMenu();
 // Loop through the commands until getCmd returns false (Quit)
 while (getCmd(widgets, accepted, returned,
               sent, maxpending, pending)) cmdLoop(widgets);
 return 0;
}

/***********************************
** Function: drawMenu()
** Description: Draws the help menu.
** Return: void
** Arguments: NULL
***********************************/
void drawMenu() {
 cout << string(38, '-') << endl;
 cout << "Choose from following commands:\n";
 cout << "L --- list the current inventory level;\n";
 cout << "R --- handle a request from the customer;\n";
 cout << "S --- handle a shipment from the supplier;\n";
 cout << "Q --- terminate the program;\n";
 cout << "H --- display this help message.\n";
 cout << string(38, '-') << endl;
}

/***********************************
** Function: getCmd()
** Description: Takes users input,
** calls whichever function they requested.
** Return: true on all except quite
** Arguments: widgets as int&, accepted as int&,
** returned as int&, sent as int&, maxpending as int&,
** pending as int&.
***********************************/
bool getCmd(int &widgets, int &accepted, int &returned,
           int &sent, int &maxpending, int &pending) {
 char cmd;
 cout << "Enter your choice: ";
 cin >> cmd;
 switch (tolower(cmd)) {
   case 'l':
     // Call list inv function
     listInv(widgets);
   break;
   case 'r':
     request(pending, sent, widgets, maxpending);
     // Call request function
   break;
   case 's':
     // Call shipment function
     recvShip(accepted, pending, sent, widgets, returned);
   break;
   case 'h':
     // Draw the menu
     drawMenu();
   break;
   case 'q':
     quit (accepted, returned, sent, maxpending, widgets);
     // Call quit status function
     return false;
   break;
   default:
     cout << "Invalid command.\n";
   break;
 }
 return true;
}

/***********************************
** Function: listInv()
** Description: Prints inventory levels
** Return: void
** Arguments: widgets as int
***********************************/
void listInv(int widgets) {
 cout << "Number of widgets in inventory: " << widgets << endl;
}

/***********************************
** Function: recvShip()
** Description: Recieves a shipment.
** Asking for amount, fills pending,
** returns unneeded.
** Return: void
** Arguments: accepted as int&, pending as int&,
** sent as int&, widgets as int&, returned as int&.
***********************************/
void recvShip(int &accepted, int &pending, int &sent,
             int &widgets, int &returned) {
 int amt;
 amt = getPosInt("Enter the shipment amount: ");
 accepted += amt;
 if (pending > 0)
 {
   if (amt - pending >= 0)
   {
     sent += pending;
     amt -= pending;
     cout << pending
          << " widgets have been used to fulfil pending request(s)."
          << endl;
     pending = 0;
   } else {
     sent += amt;
     cout << amt
          << " widgets have been used to fulfil pending request(s)."
          << endl;
     pending -= amt;
     amt = 0;
   }
 }
 if (widgets + amt <= maxWidgets)
 {
   widgets += amt;
   cout << amt << " widgets have been stored.\n";
 }
 else
 {
   int dec = amt - (maxWidgets - widgets);
   returned += dec;
   accepted -= dec;
   amt = amt - dec;
   widgets = maxWidgets;
   if (amt > 0)
     cout << amt << " widgets have been stored." << endl;
   cout << dec
        << " widgets have been sent back due to lack of space.\n";
 }
}

/***********************************
** Function: request()
** Description: Take and fill to ability
** a customers request.
** Return: void
** Arguments: pending as int&, send as int&,
** widgets as int&, maxpending as int&.
***********************************/
void request(int &pending, int &sent,
            int &widgets, int &maxpending) {
 int amt;
 amt = getPosInt("Enter the request amount: ");
 if (amt <= widgets) { // Enough widgets
   widgets -= amt;
   sent += amt;
   cout << amt
        << " widgets of the request have been fulfilled.\n";
 } else if (amt <= (widgets + (100 - pending))) {
   if (widgets > 0) {
     sent += widgets;
     cout << widgets
          << " widgets of the request have been fulfilled.\n";
     amt -= widgets;
     widgets = 0;
   }
   pending += amt;
   if (pending > maxpending) maxpending = pending;
   cout << amt
        << " widgets of the request have been"
        << " entered into a pending list.\n";
 } else {  // Not enough widgets
   cout << "The request of "
        << amt
        << " widgets has been rejected.\n";
 }
}

/***********************************
** Function: quit()
** Description: Exit program. Print out
** final values.
** Return: void
** Arguments: accepted as int, returned as int,
** sent as int, maxpending as int, widgets as int.
***********************************/
void quit(int accepted, int returned, int sent,
         int maxpending, int widgets) {
 cout << endl << "==== Statistics ====\n\n";
 cout << "Widgets accepted from supplier:" << setw(8)
                                           << accepted << endl;
 cout << "Widgets returned to supplier  :" << setw(8)
                                           << returned << endl;
 cout << "Widgets sent to customers     :" << setw(8)
                                         << sent << endl;
 cout << "Maximum widgets pending       :" << setw(8)
                                         << maxpending << endl;
 cout << "Number of widgets in inventory:" << setw(8)
                                           << widgets << "\n\n";

 cout << "==== End of run ====" << endl;
}

/***********************************
** Function: getPosInt()
** Description: Gets a users input,
** only accepts positive integers.
** Return: input as int
** Arguments: question as string
***********************************/
int getPosInt(string q) {
 int amt = 0;
 while (cout << q)
 {
   cin >> amt;
   if (cin.fail()) {
     cin.clear();
     cin.ignore(numeric_limits<streamsize>::max(),'\n');
     amt = 0;
   }
   if (amt <= 0)
     cout << "The amount must be a positive number.\n";
   else
     break;
 }
 return amt;
}

/***********************************
** Function: cmdLoop()
** Description: Run every command loop,
** prints out if the user is low on stock.
** Return: void
** Arguments: widgets as int.
***********************************/
void cmdLoop(int widgets) {
 if (widgets < minWarning) {
   cout << "\nWarning! The current inventory level is too low.";
   cout << "\n         Order a new shipment ASAP.\n\n";
 }
}