/***********************************
** Author: Steven Scott
** Filename: pex6.cpp
** Date: Nov 19, 2007
** Purpose: Keep track of inventory
** levels for a company using linked
** lists.
***********************************/
#include <iostream>
#include <iomanip>
#include <list>
using namespace std;

/*****************************
**  Struct for pending items.
*****************************/
struct pendingItem {
 int pending;
 string customer;
 pendingItem *nextItem;
};

/*****************************************
** Define named constants
******************************************/
const int maxWidgets = 500;
const int minWarning = static_cast<int>(maxWidgets * 0.1);
const int pendingLimit = 100;

const char cList = 'L';
const char cReq  = 'R';
const char cShip = 'S';
const char cQuit = 'Q';
const char cHelp = 'H';

/***********************************************
** Ok, now tell me if you recommend this now?
** Define functions for later use.
***********************************************/

/***********************************
** Function: drawMenu()
** Description: Draws the help menu.
***********************************/
void drawMenu();

/***********************************
** Function: getCmdAndParse()   (Happy?)
** Description: Takes users input,
** calls whichever function they requested.
***********************************/
bool getCmdAndParse(int &widgets, int &accepted, int &returned,
           int &sent, int &maxpending, int &pending,
           list<pendingItem> &pendingList);

/***********************************
** Function: listInv()
** Description: Prints inventory
** and pending levels.
***********************************/
void listInv(int widgets, list<pendingItem> &pendingList);

/***********************************
** Function: recvShip()
** Description: Recieves a shipment.
** Asking for amount, and customer,
** fills pending, returns unneeded.
***********************************/
void recvShip(int &accepted, int &pending, int &sent,
             int &widgets, int &returned,
             list<pendingItem> &pendingList);

/***********************************
** Function: request()
** Description: Take and fill to ability
** a customers request, add rest to pending
***********************************/
void request(list<pendingItem> &pendingList, int &sent, int &widgets,
            int &maxpending, int &pending);

/***********************************
** Function: cmdLoop()
** Description: Run every command loop,
** prints out if the user is low on stock.
***********************************/
void cmdLoop(int widgets);

/***********************************
** Function: quit()
** Description: Exit program. Print out
** final values.
***********************************/
void quit(int accepted, int returned, int sent,
         int maxpending, int widgets, list<pendingItem> &pendingList);

/***********************************
** Function: getPosInt()
** Description: Gets a users input,
** only accepts positive integers.
***********************************/
int getPosInt(string q);

/***********************************
** Function: printPending()
** Description: Prints the current list
** of pending transactions.
***********************************/
void printPending(list<pendingItem> &pendingList);

/***********************************
** Function: getString()
** Description: Gets a string from
** the user
***********************************/
string getString(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;
 // Create the list for pending items.
 list<pendingItem> pendingList;

 // Draw the help menu
 drawMenu();
 // Loop through the commands until getCmd returns false (Quit)
 while (getCmdAndParse(widgets, accepted, returned, sent,
        maxpending, pending, pendingList))
   cmdLoop(widgets);
 return 0;
}

/***********************************
** Function: drawMenu()
** Description: Draws the help menu.
***********************************/
void drawMenu() {
 cout << string(38, '-') << endl;
 cout << "Choose from following commands:\n";
 cout << cList << " --- list the current inventory level;\n";
 cout << cReq << " --- handle a request from the customer;\n";
 cout << cShip << " --- handle a shipment from the supplier;\n";
 cout << cQuit << " --- terminate the program;\n";
 cout << cHelp << " --- display this help message.\n";
 cout << string(38, '-') << endl;
}

/***********************************
** Function: getCmdAndParse()   (Happy?)
** Description: Takes users input,
** calls whichever function they requested.
***********************************/
bool getCmdAndParse(int &widgets, int &accepted, int &returned,
           int &sent, int &maxpending, int &pending,
           list<pendingItem> &pendingList) {
 string tmp = getString("\nEnter your choice: ");
 char cmd = tmp[0];
 switch (toupper(cmd)) {
  case cList:
    // Call list inv function
    listInv(widgets, pendingList);
  break;
  case cReq:
    request(pendingList, sent, widgets, maxpending, pending);
    // Call request function
  break;
  case cShip:
    // Call shipment function
    recvShip(accepted, pending, sent, widgets, returned, pendingList);
  break;
  case cHelp:
    // Draw the menu
    drawMenu();
  break;
  case cQuit:
    quit (accepted, returned, sent, maxpending, widgets, pendingList);
    // Call quit status function
    return false;
  break;
  default:
    cout << "--- Invalid command.\n";
  break;
 }
 return true;
}

/***********************************
** Function: listInv()
** Description: Prints inventory
** and pending levels.
***********************************/
void listInv(int widgets, list<pendingItem> &pendingList) {
 cout << "--- Number of widgets in inventory: " << widgets << endl;
 printPending(pendingList);
}

/***********************************
** Function: recvShip()
** Description: Recieves a shipment.
** Asking for amount, and customer,
** fills pending, returns unneeded.
***********************************/
void recvShip(int &accepted, int &pending, int &sent,
             int &widgets, int &returned,
             list<pendingItem> &pendingList) {
 int amt;
 amt = getPosInt("Enter the shipment amount: ");
 accepted += amt;
 // If there is a pending list, make sure to fill it.
 if (pendingList.size() > 0)
 {
   // Create an iterator to the first element. No need to increase it.
   list<pendingItem>::iterator iter = pendingList.begin();
   while (pendingList.size() > 0) {
     // Loop through, removing pending items while we have the widgets.
     if (amt >= iter->pending) {
       cout << "--- " << iter->pending << " widgets have been sent to "
            << iter->customer << ".\n";
       sent += iter->pending;
       amt -= iter->pending;
       pending -= iter->pending;
       iter = pendingList.erase(iter);
     } else if (amt > 0) {
       // If we can partially fill an order, do it.
       cout << "--- " << amt << " widgets have been sent to "
            << iter->customer << ".\n";
       iter->pending -= amt;
       pending -= pending;
       sent += amt;
       amt = 0;
       break;
     } else {
       break;
     }
   }
 }
 // Once done pending list, check if there's anything left to recieve
 if (amt > 0) {
   // See if it will fill up the inventory or not
   if (widgets + amt <= maxWidgets) {
     cout << "--- " << amt << " widgets have been stored.\n";
     widgets += amt;
   } else {
     // Figure out how much to decline
     int dec = amt - (maxWidgets - widgets);
     returned += dec;
     accepted -= dec;
     amt -= dec;
     widgets += amt;
     if (amt > 0)
       cout << "--- " << amt << " widgets have been stored.\n";
       cout << "--- " << dec << " widgets have been sent "
       << "back due to lack of storage space.\n";
   }
 }
}

/***********************************
** Function: request()
** Description: Take and fill to ability
** a customers request, add rest to pending
***********************************/
void request(list<pendingItem> &pendingList, int &sent,
            int &widgets, int &maxpending, int &pending) {
 int amt;
 string cust;
 // Get customer name and amount.
 cust = getString("Enter the name of the customer: ");
 amt = getPosInt("Enter the request amount: ");
 if (amt <= widgets) {
   // There's enough widgets to fill order, do so.
   widgets -= amt;
   sent += amt;
   cout << "--- " << amt << " widgets have been sent to "
       << cust << ".\n";
 } else {
   if (widgets > 0) {
     // If there's widgets, fill request to ability.
     sent += widgets;
     cout << "--- " << widgets << " widgets have been sent to "
          << cust << ".\n";
     amt -= widgets;
     widgets = 0;
  }
  // Add unfilled to a new pendingItem. Add that to pendingList
  pendingItem *pend = new pendingItem;
  pend->customer = cust;
  pend->pending = amt;
  pendingList.push_back(*pend);
  pending += amt;
  if (pending > maxpending) maxpending = pending;
  cout << "--- " << amt << " widgets requested by " << cust
       << " have been entered into a pending list.\n";
 }
}

/***********************************
** Function: quit()
** Description: Exit program. Print out
** final values.
***********************************/
void quit(int accepted, int returned, int sent,
         int maxpending, int widgets, list<pendingItem> &pendingList) {
 // Print out the list of pending items.
 printPending(pendingList);
 // Print out other stats.
 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;

 // Clear the pending list and free the memory.
 pendingList.clear();
 delete(&pendingList);
}

/***********************************
** Function: getPosInt()
** Description: Gets a users input,
** only accepts positive integers.
***********************************/
int getPosInt(string q) {
 int amt = 0;
 // Loop until a valid answer
 while (cout << q)
 {
  cin >> amt;
  // If there is something wrong, clear cin for proper useage.
  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;
 }
 // Clear cin so that getline doesn't complain
 cin.ignore(numeric_limits<streamsize>::max(),'\n');
 return amt;
}

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

/***********************************
** Function: printPending()
** Description: Prints the current list
** of pending transactions.
***********************************/
void printPending(list<pendingItem> &pendingList) {
 cout << "--------------------" << endl;
 // If there is a pending list, print it.
 if (pendingList.size() > 0) {
   cout << "--- Number of requests pending:" << setw(11)
        << pendingList.size() << endl;
   // Loop from the beginning to the end of the pending list and print.
   list<pendingItem>::const_iterator iter;
   for (iter = pendingList.begin(); iter != pendingList.end(); iter++)
   {
     cout << "--- " << iter->pending;
     cout << " widgets need to be sent to ";
     cout << iter->customer << ".\n";
   }
 } else
   // Else, print that there is none.
   cout << "--- No pending requests.\n";

 cout << "--------------------" << endl;
}

/***********************************
** Function: getString()
** Description: Gets a string from
** the user
***********************************/
string getString(string q) {
 string a;
 cout << q;
 getline( cin, a );
 return a;
}