#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
#include <math.h>
#include <cmath>

using namespace std;

class Polynomial {
    float a, b, c, value;

public:
    Polynomial ();
    void functionDefine(Polynomial poly);
    void functionValue(Polynomial poly);
    void functionZero(Polynomial poly);
    //void functionMonoty(Polynomial poly);
};

namespace Utils {
    void mainMenu(Polynomial poly);
    void skipToMenu();
    string save(string str);
    int exitProgram();

    void mainMenu(Polynomial poly) {
        int choice = 0;

        cout << "   ---------- Main Menu ----------" << endl;

        cout << "1: ---- Define New Polynomial ----" << endl;
        cout << "2: ------ Solve for x-value ------" << endl;
        cout << "3: --------- Find roots ----------" << endl;
        cout << "4: ------------ Exit -------------" << endl << endl;

        cout << "Enter the value of the submenu you want to enter: ";

        cin >> choice;
        cout << endl;

        switch(choice) {

            case 1:
                poly.functionDefine(poly);
                break;

            //case 2:
            //  poly.functionMonoty(poly);
            //  break;

            case 2:
                poly.functionValue(poly);
                break;

            case 3:
                poly.functionZero(poly);
                break;

            case 4:
                exitProgram();
                break;
        }
    }

    void skipToMenu() {
        cout << "Press enter to return to the main menu."<< endl << endl;
        system("pause > nul");

    }

    string save(string str)  {
        string saved = "Yes or no"; // To do.
        return saved;
    }

    int exitProgram() {
        return 0;
    }
}

Polynomial::Polynomial() {
    a = 0;
    b = 0;
    c = 0;

}

void Polynomial::functionDefine (Polynomial poly) {
    char currentChar = 'a';

    cout << "---- Define New Polynomial ----" << endl;

    for (int i = 0; i < 3; i++) {
        cout << "Enter a value for " << currentChar << ": ";

        switch(i)
        {
            case 0:
                cin >> poly.a; break;
            case 1:
                cin >> poly.b; break;
            case 2:
                cin >> poly.c; break;
        }

        if (!cin) {
            cout << "Please enter a number instead." << endl;
            system("pause");
        }

        currentChar = static_cast<char>(currentChar + 1);

    }

    cout << endl;
    cout << "The function is: f(x) = " << poly.a << "x^2 + " << poly.b << "x + " << poly.c << "." << endl << endl;

    Utils::skipToMenu();
    Utils::mainMenu(poly);

}

void Polynomial::functionValue(Polynomial poly) {
    int input;

    cout <<"------ Solve for x-value ------" << endl << endl;

    cout << "Enter the x-value that you would like to evaluate the equation for: ";
    cin >> input;

    value = poly.a * pow(input, 2) + poly.b * input + poly.c;
    cout << "The value of the function for x = " << input << " is " << value << endl << endl;

    Utils::mainMenu(poly);
}

void Polynomial::functionZero(Polynomial poly) {
    float d = pow(poly.b, 2) - 4 * poly.a * poly.c;

    if (d > 0) {

        float result = ((-poly.b) + sqrt(abs(d))) / (2 * poly.a);
        float secondResult = (-poly.b - sqrt(abs(d))) / (2 * poly.a);
        cout << "The polynomials roots are at x = " << result << " and x = " << secondResult << "." << endl << endl;
    }

    else if (d == 0) {
        float result = ((-b) + sqrt(abs(d))) / (2 * a);
        cout << "The polynomials root is at x = " << result << "." << endl << endl;
    }

    else {
        cout << "The polynomial has no roots." << endl << endl;
    }

    Utils::mainMenu(poly);
}
 /*
void Polynomial::functionMonoty(Polynomial poly) {



}
*/
int main () {
    Polynomial poly;
    Utils::mainMenu(poly);

    return 0;
}