#include <iostream>
#include <cctype>
#include <string>
#include <sstream>
#include <fstream>
using namespace std;

const char Number_Puzzle = 'A';
const char Number_Mirror = 'B';
const char GCD_Finder = 'C';
const char Quit = 'Q';
const char FILLCHAR = '*';
const int MAXSIZE = 101;

char PickYourPuzzle();

void NumberPuzzle(ifstream& fin, const string filename);
void FillPuzzleArrays(ifstream& fin, int arry[], int index, int& size);
bool Solvable(int position, int squares[], int nSquares);
int NumPuzzleReturn(int i, int puzzle[], int index, int& size, int previndex);

void NumberMirror();
int WriteNumBackwards(string snum, int i);

void GCDFinder();
int CalculateGCD(int a, int b);


void main()
{
    char choice;
    ifstream fin;
    string filename;
    int puzzle[MAXSIZE];
    int index = 0;
    int size;
    int i = 0;
    int previndex = 0;
    do
    {
        choice = PickYourPuzzle();
        switch (choice)
        {
        case Number_Puzzle:    NumberPuzzle(fin, "puzzle.txt");
                            FillPuzzleArrays(fin, puzzle, index, size);
                            NumPuzzleReturn(i, puzzle, index, size, previndex);
            break;
        case Number_Mirror:    NumberMirror();
            break;
        case GCD_Finder: GCDFinder();
            break;
        case Quit:    cout<< "Goodbye my friend" << endl << endl;
            break;
        }
    }while(choice != Quit);
}

char PickYourPuzzle()
{
    char choice;

    cout<< "Hello welcome to the Puzzle Center." << endl
        << "What puzzle would you like to try your hand at." << endl << endl;
    cout<< "A) Number Puzzle Solver: Solves a number puzzle. " << endl
        << "B) Number Mirror: Displays a number 'backwards'. " << endl
        << "C) GCD Finder: This finds the greatest vommon divisor of two numbers. " << endl
        << "Q) Quit the program. " << endl << endl;
    cout<< "Your Choice? ";
    cin >> choice;
    choice = toupper(choice);

    if( choice == Number_Puzzle || choice == Number_Mirror || choice == GCD_Finder)
    {
        cout<< endl << "Thank You for choosing " << choice << ". One Moment Please." << endl << endl;
    }
    else if(choice == Quit)
    {
        cout<< endl;
    }
    else
    {
        cerr<< "That is an INVAILD CHOICE! Please choose again." << endl << endl;
    }
    
    return(choice);
}

void NumberMirror()
{
    string snum;
    int number;
    int i;

    cout<< "Welcome to the Number Mirror Puzzle. " << endl;
    cout<< "Please enter a non-negative integer to be mirrored! ";
    cin >> snum;
    istringstream iss(snum);
    iss >> number;
    while(number < 0)
    {
        cout<< "That is not a non-negaitve integer! Try again." << endl;
        cin >> snum;
        istringstream iss(snum);
        iss >> number;
    }
    i = snum.length();
    cout<< "The mirror of " << snum << " is";
    WriteNumBackwards(snum, i);
    cout<< endl << endl;
}
int WriteNumBackwards(string snum, int i)
{
    if (i < 0)
    {
        return(0);
    }
    else
    {
        cout<< snum[i];
        return(WriteNumBackwards(snum, i-1));
    }

}

void GCDFinder()
{
    int number1;
    int number2;
    int big, little;
    int gcd;

    cout<< "Welcome to the Greatest Common Divisor Finder." << endl
        << "Please enter the first number: ";
    cin >> number1;
    cout<< "Please enter the second number: ";
    cin >> number2;
    if (number1 > number2)
    {
        big = number1;
        little = number2;
    }
    if (number1 < number2)
    {
        little = number1;
        big = number2;
    }
    gcd = CalculateGCD(big, little);
    cout<< "The greatest common denominator of " << big
        << " and " << little << " is " << gcd << "." << endl << endl;
}
int CalculateGCD(int a, int b)
{
    int r;
    r = a % b;
    if( r == 0 )
    {
        return(b);
    }
    else
    {
        return(CalculateGCD(b, r));
    }
    
}
void NumberPuzzle(ifstream& fin, const string filename)
{
    fin.open(filename.c_str());

}
void FillPuzzleArrays(ifstream& fin, int arry[], int index, int& size)
{
    string puzsize;
    
    string strnum;
    int num;
    getline(fin, puzsize, ' ');
    istringstream iss(puzsize);
    iss >> size;
    getline(fin, strnum, ' ');
    do
    {
        istringstream iss(strnum);
        iss >> num;
        arry[index] = num;
        index++;
        getline(fin, strnum, ' ');
    }while(index < size);
    cout<< "Solving puzzle 1. Puzzle size = " << size << endl;
    system("pause");
}
int NumPuzzleReturn(int i, int puzzle[], int index, int& size, int previndex)
{
    int newindex;
    bool flag2;
    int j = 0;
    j = puzzle[previndex];
    i = puzzle[index];
    if(i == 0)
    {
        return(0);
    }
    else
    {
        flag2 = Solvable(index, puzzle, size);
        if(flag2 == true)
        {
            cout<< "Entering Solvalble() at index " << index << "(" << i << ")" << endl;
            previndex = index;
            newindex = (index+i);
            puzzle[index] = FILLCHAR;
            return(NumPuzzleReturn(i, puzzle, newindex, size, previndex));
        }
        if(flag2 == false)
        {
            cout<< "Index " << index << " is not in the array. Returning false." << endl;
            //i = ((i - puzzle[index])+ index);
            index = previndex;
            newindex = (index-i);
            puzzle[index] = FILLCHAR;
            return(NumPuzzleReturn(i, puzzle, index, size, previndex));
        }
    }
}
bool Solvable(int position, int squares[], int nSquares)
{
    bool flag;

    if((position < 0) || (position > nSquares) || (squares[position] == FILLCHAR))
    {
        flag = false;
    }
    else
    {
        flag = true;
    }
    return(flag);
}