/*
    testfunc16.cpp
    CIS 150
    2008-06-10
    David Klick
   
    Recursive solution to Towers of Hanoi.
*/

#include <iostream>
#include <cstring>
using std::cin;
using std::cout;

int getInt(char* prompt, int min, int max);
char getChoice(char* prompt, char* allowed);
void moveDisks(int numDisks, int fromPole, int toPole);
void cont();

int main(int argc, char* argv[]) {
    int disks;    // number of disks to be moved
    char ans;     // holds user answer for "play again?"
   
    do {
        // get number of disks from user (1 to 10)
        disks = getInt("Enter number of disks (1-10): ", 1, 10);
   
        // move all disks from first pole to third pole
        cout << "Moving " << disks << " disks from pole 1 to pole 3\n";
        moveDisks(disks, 1, 3);
      
        // find out if user wants to play again
        ans = getChoice("Would you like to play again? (Y/N) ", "YyNn");
    } while (ans == 'Y');

    // say "Goodnight" Gracie
    cout << "Normal program termination.\n";
    cont();
    return 0;
}

/*
    int getInt(char* prompt, int min, int max);
   
    Arguments:
        prompt: a pointer to a C-style string to be used as a prompt
        min: the minimum value allowed to be entered
        max: the maximum value allowed to be entered
   
    Returns: an integer entered by the user
   
    Prompts user with message passed in as argument and returns
    the integer value entered. The number must be between min and
    max (inclusive) or the user will be reprompted to enter
    another number. Note: For simplicity, no error checking on
    input is done, therefore this function may crash the program
    on invalid input.
*/
int getInt(char* prompt, int min, int max) {
    int num;
    do {
        cout << prompt;
        cin >> num;
        if (num < min) cout << "Error: value below minimum allowed\n";
        else if (num > max) cout << "Error: value above maximum allowed\n";
    } while (num<min || num>max);
    return num;
}

/*
    char getChoice(char* prompt, char* allowed);
   
    Arguments:
        char* prompt: a C-style string containing the prompt to show the user
        char* allowed: a C-style string containing all allowed user responses
            (each valid response being a single character)
   
    Returns: the user's choice (a character)
   
    Displays a prompt and then waits for the user to
    enter an allowed choice (a single character). Once
    a valid choice has been made, the function returns
    it to the calling function.
*/
char getChoice(char* prompt, char* allowed) {
    char ans;
    do {
        cout << prompt;
        cin >> ans;
        ans = toupper(ans);  // convert answer to upper case
        if (strchr(allowed, ans) == NULL) cout << "Error: Invalid choice\n";
   } while (strchr(allowed, ans) == NULL);
   return ans;
}


/*
    void moveDisks(int numDisks, int fromPole, int toPole);
   
    Arguments:
        int numDisks: the number of disks to be moved
        int fromPole: the pole to move the disks from (s/b 1, 2, or 3)
        int toPole: the pole to move the disks to (s/b 1, 2, or 3,
            and not be the same as the fromPole)
   
    Returns: nothing
   
    Effects: Displays the solution to the Towers of Hanoi problem
        on the screen move-by-move.

    This function solves the Towers of Hanoi problem by
    recursively moving disks from pole to pole. If there
    is only one disk to be moved, the routine moves it
    and is done. If there is more than one disk to be moved,
    it moves the stack of disks in pieces so that it calls
    this method again with fewer disks to be moved.
    Eventually, all calls result in moves of a single disk
    which can be easily solved.
*/
void moveDisks(int numDisks, int fromPole, int toPole) {
    int otherPole = 6 - fromPole - toPole;
    if (numDisks == 1) {
        cout << "Move disk from " << fromPole
             << " to " << toPole << '\n';
    } else {
        moveDisks(numDisks-1, fromPole, otherPole);
        cout << "Move disk from " << fromPole
             << " to " << toPole << '\n';
        moveDisks(numDisks-1, otherPole, toPole);
    }
}

/*
    void cont();
   
    Arguments: none
   
    Returns: nothing
   
    Clears input buffer and pauses waiting for user 
    to press Enter.
*/
void cont() {
    if (cin.rdbuf()->sungetc() != -1 && cin.get() != '\n') cin.ignore(80,'\n');
    cout << "Press enter to continue...";
    cin.get();
}