/* Filename:  list2.cpp

   Author:  Br. David Carlson

   Date:  July 5, 1999

   Last Revised:  September 19, 2022

   This interactive program allows the user to insert integers into
   a list, sort them, find their average, find their maximum value, and print them.

   Tested with:
      Microsoft Visual C++ 2019
*/

#include <iostream>
#include <list>
#include <algorithm>
#include <iterator>
#include <cctype>   // to use the toupper function

using namespace std;


// Function prototypes:
template <class T> void Print(list<T>& L);

char MenuChoice(void);

int GetNum(void);

void InsertBefore(list<int>& L);

void Average(list<int>& L);


int main(void)
{
    list<int> L;
    char Choice;
    int Num;

    Choice = MenuChoice();

    while (Choice != 'H')
    {
        if (Choice == 'A')
        {
            Num = GetNum();
            L.push_back(Num);
        }
        else if (Choice == 'B')
        {
            Num = GetNum();
            L.push_front(Num);
        }
        else if (Choice == 'C')
            InsertBefore(L);
        else if (Choice == 'D')
            L.sort();
        else if (Choice == 'E')
            Print(L);
        else if (Choice == 'F')
            Average(L);
        else if (Choice == 'G')
        {
            if (L.size() == 0)
                cout << "No maximum can be found since the list is empty" << endl;
            else
                cout << "Max value is " << *max_element(L.begin(), L.end()) << endl;
        }
        else if (Choice != 'H')
            cout << "Invalid choice" << endl;

        Choice = MenuChoice();
    }

    return 0;
}


/* Given:  Nothing.
   Task:   To present the menu of available options and get the letter
           representing the user's menu choice.
   Return: This letter (translated to upper case) in the function name.
*/
char MenuChoice(void)
{
    char Ch;

    cout << endl << "Menu of Available Options" << endl;
    cout << "   A)   Insert at the rear of the list" << endl;
    cout << "   B)   Insert at the front of the list" << endl;
    cout << "   C)   Insert before a specific item" << endl;
    cout << "   D)   Sort the list" << endl;
    cout << "   E)   Print the list" << endl;
    cout << "   F)   Find the average of the items in the list" << endl;
    cout << "   G)   Find the maximum item in the list" << endl;
    cout << "   H)   Quit" << endl;
    cout << "Enter the letter for your choice: ";
    cin >> Ch;
    cin.get();   // read in and discard the ENTER
    return toupper(Ch);
}


/* Given:  Nothing.
   Task:   To get an integer from the user.
   Return: This integer in the function name.
*/
int GetNum(void)
{
    int Temp;

    cout << "Enter integer to be inserted: ";
    cin >> Temp;
    cin.get();
    return Temp;
}


/* Given:  L    List of integers.
   Task:   To prompt the user for a number to insert into L and for the
           number in L before which to insert the new number.  Does the
           insertion (unless it cannot find the number before which to
           insert).
   Return: L    Updated list of integers.
*/
void InsertBefore(list<int>& L)
{
    int Item, Target;
    list<int>::iterator p;

    Item = GetNum();
    cout << "Insert this number before what number? ";
    cin >> Target;
    cin.get();

    p = find(L.begin(), L.end(), Target);
    if (p == L.end())
        cout << "Sorry, could not find " << Target << " so " << Item
           << " not inserted" << endl;
    else
        L.insert(p, Item);
}


/* Given:  L   List of integers.
   Task:   To find and print the average of the numbers in list L.
   Return: Nothing.
*/
void Average(list<int>& L)
{
    int Count;
    float Sum;
    list<int>::iterator p;

    Count = L.size();
    if (Count == 0)
        cout << "No average can be found since the list is empty" << endl;
    else
    {
        Sum = 0.0;
        for (p = L.begin(); p != L.end(); p++)
            Sum = Sum + *p;
        cout << "Average is " << Sum / Count << endl;
    }
}


/*  Given:   L    A list containing items of type T.
    Task:    To print out the contents of list L.
    Assumes: Items of type T can be printed using <<.
    Return:  Nothing.
*/
template <class T> void Print(list<T>& L)
{
    cout << "Contents of list:" << endl;
    copy(L.cbegin(), L.cend(), ostream_iterator<T>(cout, " "));
    cout << endl << endl;
}