#include <iostream>
#include <math.h>
#include <iomanip>

using namespace std;

//Define MathOperator as a function that requires 2 doubles to be passed.
//This will allow me to store all my 2 operand functions into an array to avoid
//unneeded switch/if statements
typedef double (*MathOperator) (double a, double b);

//Declare all my functions
double getAdditionResult(double a, double b);
double getMultiplicationResult(double a, double b);
double getSubtractionResult(double a, double b);
double getDivisionResult(double a, double b);
double getExponentiationResult(double a, double b);
double getSquareRoot(double a);

//Store my operator list into a char array for display purposes later in the program
char operatorList[] = {
    '+', '-', '*', '/', '^'
};

//Constants for the teaching mode and calculator mode
//Yes I know calculator mode is not used in the program,
//but a defined constant should be here regardless.
const int MODE_TEACHING = 1;
const int MODE_CALCULATOR = 2;

/**
*   Psuedocode:
*   Initialize variables that will be used throughout the main method
*       -Create an array of 2 operand functions that can be used later on
*   Print out the menu of possible operations for the user
*   Request that the user select an operation
*       -Require the user to input a number between 1 and 6 for the operations
*   Display the possible modes for the user to select
*       -1 for teaching, 2 for calculator
*       -Require the user to select 1 or 2
*
*   If the selected operation is the square root operation:
*       Ask the user to input the number to be square rooted
*           If the mode is in teaching mode ask the user to input what they think is the answer
*               -If they are right, print out congratulations and terminate the program
*               -If they are wrong, tell them they are wrong. The program will print out the answer later
*           Print out the solution and terminate the program
*
*   Otherwise,
*   Tell the user they are performing a 2 operator function in the format A + B, A - B, ect.
*   Require the user to input the A and B operands
*   Calculate the result
*   If the mode is in teaching
*       Ask the user to input what they think is the right answer
*           -If they are right display a congratulations message and terminate the program
*           -If they are wrong then tell them they are wrong. The program will print out the answer later
*   Print out the operation being performed. Ex. 8 + 4
*   Print out the result of the answer and terminate the program.
* */
int main()
{
    //Initialization of variables that will be used throughout the program
    int selectedOperation;
    int selectedMode;
    double leftOperand;
    double rightOperand;
    double inputtedGuess;
    double result;

    //Store all my 2 operand functions into an array of "MathOperator" that was typedef'd above
    MathOperator operators[] = {
        getAdditionResult,
        getSubtractionResult,
        getMultiplicationResult,
        getDivisionResult,
        getExponentiationResult,
    };

    //Print out the operations list that the user can select
    cout << "Operations List\n";
    cout << "\t1. (+) Addition\n";
    cout << "\t2. (-) Subtraction\n";
    cout << "\t3. (*) Multiplication\n";
    cout << "\t4. (/) Division\n";
    cout << "\t5. (a^b) Exponentiation\n";
    cout << "\t6. (sqrt(a)) Square Root\n";

    //Request that the user select an operation and require them to pick a number between 1 and 6
    cout << "Please select an operation to use(1-6): ";
    cin >> selectedOperation;

    while (selectedOperation < 1 || selectedOperation > 6) {
        cout << "Please select an appropriate operation between 1 and 6: ";
        cin >> selectedOperation;
    }

    //Print out the possible modes the user can select.
    cout << "Modes\n";
    cout << "\t1. Teaching Mode\n";
    cout << "\t2. Calculator Mode\n";

    //Request that the user selects a mode and require them to select either 1 or 2.
    cout << "Please select a mode to use: ";
    cin >> selectedMode;
    while (selectedMode < 1 || selectedMode > 2) {
        cout << "Please select either 1 or 2 for your teaching mode: ";
        cin >> selectedMode;
    }

    /**********
    *   Single operand function
    ***********/

    //Sqrt is the only operator that requires 1 variable
    //Manually perform this operation since it is the only 1 operand function
    if (selectedOperation == 6) {
        //Request the user to enter a number to square root
        cout << "Enter a number to square root: ";
        cin >> leftOperand;

        //If this number is less than 0, the result is an imaginary number. We are not calculating this.
        //Alert the user and terminate the program.
        if (leftOperand < 0) {
            cout << "Cannot calculate the square root of a negative number.\n";
            return 0;
        }

        //Store the result into 'result'
        result = getSquareRoot(leftOperand);

        //If the selected mode is teaching
        if (selectedMode == MODE_TEACHING) {

            //Ask the user what they think the answer is and store it into inputted guess
            cout << "What do you think the answer is?: ";
            cin >> inputtedGuess;

            //If they are right the display the congrats message and terminate the program
            //Otherwise tell the user they are wrong.
            if (inputtedGuess == result) {
                cout << "Congrats! You got the answer right!\n";
                return 0;
            } else {
                cout << "Sorry, that was not the correct answer.\n";
            }
        }

        //Display the result and terminate the program after flushing cout.
        cout << "The result is: " << result << endl;
        return 0;
    }

    /**********
    *   Double operand function
    ***********/

    //Tell the user they are performing a 2 operand function
    cout << "You are performing a 2 operand function. This is the format\n";

    //Display the format. Ex. A + B, A - B, ect based off what they selected earlier
    cout << "\tA " << operatorList[selectedOperation - 1] << " B\n";

    //Request the user to input A and B
    cout << "Please input the values of A and B.\n";
    cout << "A: ";
    cin >> leftOperand;
    cout << "B: ";
    cin >> rightOperand;

    //Using the array of functions created earlier, I can call a specific function
    //based off what they selected and pass my 2 operands into the function
    //and store the result into 'result'.
    result = operators[selectedOperation-1](leftOperand, rightOperand);

    //If the selected mode is teaching
    if (selectedMode == MODE_TEACHING) {
        //Request the user to input their guess
        cout << "What do you think the result is?: ";
        cin >> inputtedGuess;

        //If they are right the display the congrats message and terminate the program
        //Otherwise tell the user they are wrong.
        if (inputtedGuess == result) {
            cout << "Congrats! You got the answer right!\n";
            return 0;
        } else {
            cout << "Sorry, that was not the correct answer.\n";
        }
    }

    //Print out the operation the user is doing. Ex. 9 - 4
    //Then print out the result and flush cout.
    cout << "Operation: " << leftOperand << " " << operatorList[selectedOperation - 1] << " " << rightOperand << "\n";
    cout << "The result is: " << result << endl;

    return 0;
}

/**
*   Get the result of 2 added operands
*
*   @parameter left operand
*   @parameter right operand
*   @result LeftOperand + RightOperand
*/
double getAdditionResult(double a, double b) {
    return a + b;
}

/**
*   Get the result of 2 subtracted operands
*
*   @parameter left operand
*   @parameter right operand
*   @result LeftOperand - RightOperand
*/
double getSubtractionResult(double a, double b) {
    return a - b;
}

/**
*   Get the result of 2 divided operands
*
*   @parameter left operand
*   @parameter right operand
*   @result LeftOperand / RightOperand
*/
double getDivisionResult(double a, double b) {
    return a / b;
}

/**
*   Get the result of 2 multiplied operands
*
*   @parameter left operand
*   @parameter right operand
*   @result LeftOperand * RightOperand
*/
double getMultiplicationResult(double a, double b) {
    return a * b;
}

/**
*   Get the result of an exponentiated number
*
*   @parameter left operand
*   @parameter right operand
*   @result LeftOperand ^ RightOperand
*/
double getExponentiationResult(double a, double b) {
    return pow(a, b);
}

/**
*   Square root a number
*
*   @parameter operand
*   @result The square root of the operand
*/
double getSquareRoot(double a) {
    return sqrt(a);
}