TellmyAboutBdays.cpp

//
// Tell me about your birthday!
// Created by angelos on 03/05/2020.
//
#include <ctime>
#include <iostream>
#include <string_view>

int validate_input(int lower_limit, int upper_limit, std::string_view prompt);
void year(tm &birthday);
void month(tm &birthday);
void day(tm &birthday);
bool isLeapYear(int year);
void display(const tm &birthday);

int main() {
    tm birthday{};

    std::cout << "Please submit your date of birth." << std::endl;
    year(birthday);
    month(birthday);
    day(birthday);

    display(birthday);

    return 0;
}

void year(tm &birthday) {
    birthday.tm_year = validate_input(1950, 2020, "What is the year? ");
}

void month(tm &birthday) {
    birthday.tm_mon = validate_input(1, 12, "What is the month? ");
}

void day(tm &birthday) {
    int upper_limit;
    if (birthday.tm_mon == 2) {
        if (isLeapYear(birthday.tm_year))
            upper_limit = 29;
        else
            upper_limit = 28;
    } else if (birthday.tm_mon == 1 || birthday.tm_mon == 3 || birthday.tm_mon == 5 || birthday.tm_mon == 7 || birthday.tm_mon == 8 || birthday.tm_mon == 10 || birthday.tm_mon == 12)
        upper_limit = 31;
    else
        upper_limit = 30;
    birthday.tm_mday = validate_input(1, upper_limit, "What is the day? ");
}

int validate_input(const int lower_limit, const int upper_limit, std::string_view prompt) {
    int input{};
    bool repeat{false};
    do {
        std::cout << prompt;
        std::cin >> input;
        if (input < lower_limit || input > upper_limit) {
            repeat = true;
            std::cout << "Invalid input, please try again!" << std::endl;
        } else {
            repeat = false;
        }
    } while (repeat);
    return input;
}

bool isLeapYear(const int year) {
    if (year % 4 == 0) {
        if (year % 100 == 0) {
            // the year is a leap year if it is divisible by 400.
            if (year % 400 == 0)
                return true;
            else
                return false;
        } else
            return true;
    } else
        return false;
}

void display(const tm &birthday) {
    const std::string month_names[12] = {
            "January", "February", "March", "April", "May", "June",
            "July", "August", "September", "October", "November", "December"};

    std::cout << "Your birthday is on: " << std::endl;
    std::cout << month_names[birthday.tm_mon - 1] << " " << birthday.tm_mday << ", " << birthday.tm_year << std::endl;
}