#include <cmath>
#include <iomanip>
#include <iostream>
#include <vector>

using namespace std;

int main() {
    cout << "Welcome to the Financial Calculator!\n";
    cout << endl;

    float loanAmount{};
    float interestRate{};
    float loanLength{};
    float payAmount{};
    float convertedRate{};
    int menuSelection{};

    vector<float> financialComponents;



    do {
        // Allow user to determine which calculator to enter.
        cout << "(1) Monthly Payment Calculator\n(2) Loan Amount Calculator\n(3) Loan Length "
            "Calculator\n(4) Exit\n";
        cout << endl;
        cout << "Please choose an appropriate menu option number: ";
        cin >> menuSelection;
        cout << endl;

        // Gather input and process outputs depending on which selection is made.
        // Input validation.

        while (menuSelection < 1 || menuSelection > 4) {
            cout << "Please enter a valid menu option!";
            cin >> menuSelection;
        }

        switch (menuSelection) {
        case 1:
            cout << "Please enter your loan amount: ";
            cin >> loanAmount;
            cout << "Please enter your interest rate, in decimal format: ";
            cin >> interestRate;
            cout << "Please enter your loan length (amount of monthly payments): ";
            cin >> loanLength;
            convertedRate = interestRate / 12;
            payAmount = (loanAmount * convertedRate * pow((1 + convertedRate), loanLength)) /
                (pow((1 + convertedRate), loanLength) - 1);
            cout << endl;
            // Display output to user.
            // Set precision to two for dollar amounts.

            cout << fixed << setprecision(2);
            cout << "Your monthly payment will be \t$" << payAmount << endl;
            cout << endl;

            financialComponents.push_back(loanAmount);
            financialComponents.push_back(interestRate);
            financialComponents.push_back(loanLength);
            financialComponents.push_back(payAmount);


            break;

        case 2:

            cout << "Please enter your payment amount: ";
            cin >> payAmount;
            cout << "Please enter your interest rate, in decimal format: ";
            cin >> interestRate;
            cout << "Please enter your loan length (amount of monthly payments): ";
            cin >> loanLength;
            convertedRate = interestRate / 12;
            loanAmount = (payAmount / convertedRate) * (1 - (1 / pow((1 + convertedRate), loanLength)));
            cout << endl;
            // Display output to user.
            // Set precision to two for dollar amounts.

            cout << fixed << setprecision(2);
            cout << "Your principal loan amount is \t$" << loanAmount << endl;
            cout << endl;

            financialComponents.push_back(loanAmount);
            financialComponents.push_back(interestRate);
            financialComponents.push_back(loanLength);
            financialComponents.push_back(payAmount);

            break;

        case 3:

            cout << "Please enter your loan amount: ";
            cin >> loanAmount;
            cout << "Please enter your interest rate, in decimal format: ";
            cin >> interestRate;
            cout << "Please enter your payment amount: ";
            cin >> payAmount;
            convertedRate = interestRate / 12;
            loanLength = log((payAmount / convertedRate) / ((payAmount / convertedRate) - loanAmount)) /
                log(1 + convertedRate);
            cout << endl;
            // Display output to user.
            // Display output as a rounded number of payments.
            cout << "You will have " << round(loanLength) << " payments." << endl;
            cout << endl;

            financialComponents.push_back(loanAmount);
            financialComponents.push_back(interestRate);
            financialComponents.push_back(loanLength);
            financialComponents.push_back(payAmount);

            break;

            // If 4 or an incorrect input for menu option is selected, kill program.
        }
        if (menuSelection == 4) {
            cout << "Thank you for using the Financial Calculator!\n";
            system("pause");
            return (0);
        }
    } while (menuSelection != 4);
    return 0;
}