chapter8ex1.cpp

// Osman Zakir
// 12 / 21 / 2021
// Beginning C++20: From Novice to Professional by Ivor Horton and Peter Van Weert
// Chapter 8 Exercise 1
// Exercise Specs:
/**
 * Write a function, validate_input(), that accepts two integer arguments that
 * represent the upper and lower limits for an integer that is to be entered.
 * It should accept a third argument that is a string describing the input, 
 * with the string being used in the prompt for input to be entered. The
 * function should prompt for input of the value within the range specified by
 * the first two arguments and include the string identifying the type of value to 
 * be entered. The function should check the input and continue to prompt for input 
 * until the value entered by the user is valid. Use the validate_input() function 
 * in a program that obtains a user’s date of birth and outputs it in the form of
 * this example:
 * 
 * > You were born on the 21st of November, 2012
 * 
 * The program should be implemented so that separate functions, month(), year(), and day(),
 * manage the input of the corresponding numerical values. Don’t forget leap 
 * years—February 29, 2017, is not allowed!
 */

import <iostream>;
import <format>;
import <chrono>;
import <string>;

unsigned validate_input(unsigned lower_limit, unsigned upper_limit, 
	                const std::string& description);
unsigned year(unsigned lower_limit, unsigned upper_limit);
unsigned month(unsigned lower_limit, unsigned upper_limit);
unsigned day(unsigned lower_limit, unsigned upper_limit);
unsigned get_upper_day_limit(unsigned birth_month, int birth_year);
std::string get_output_day_str(unsigned day);

int main()
{
    const auto now{ std::chrono::system_clock::now() };
	const std::chrono::year_month_day ymd{ std::chrono::floor<std::chrono::days>(now) };
	const int current_year{ static_cast<int>(ymd.year()) };
	const unsigned lower_year_limit = current_year - 160;   // lower birth year 
	                                                        // limit is 160 years ago
	const unsigned lower_month_limit{ 1 };
	const unsigned upper_month_limit{ 12 };
	const unsigned birth_year{ year(lower_year_limit, current_year) };
	const unsigned birth_month{ month(lower_month_limit, upper_month_limit) };
	const unsigned lower_day_limit{ 1 };
	const unsigned upper_day_limit{ get_upper_day_limit(birth_month, birth_year) };
	const unsigned birth_day{ day(lower_day_limit, upper_day_limit) };

	const std::string output_day_str{ get_output_day_str(birth_day) };

	std::cout << std::format("You were born on the {} of {:B}, {}\n",
	  output_day_str, std::chrono::month{ birth_month }, birth_year);
}

std::string get_output_day_str(const unsigned day)
{
	std::string output_day_str;
	std::string day_str{ std::to_string(day) };
	if (day_str.ends_with("1"))
	{
		output_day_str = day_str += "st";
	}
	else if (day_str.ends_with("2"))
	{
		output_day_str = day_str += "nd";
	}
	else if (day_str.ends_with("3"))
	{
		output_day_str = day_str += "rd";
	}
	else
	{
		output_day_str = day_str += "th";
	}
	return output_day_str;
}

unsigned get_upper_day_limit(const unsigned birth_month, const int birth_year)
{
	unsigned upper_day_limit{};
	switch (birth_month)
	{
	case 1: case 3: case 5: case 7: case 8: case 10: case 12:
		upper_day_limit = 31;
	case 4: case 6: case 9: case 11:
		upper_day_limit = 30;
	case 2:
		std::chrono::year year{ birth_year };
		if (year.is_leap())
		{
			upper_day_limit = 29;
		}
		else
		{
			upper_day_limit = 28;
		}
	}
	return upper_day_limit;
}

unsigned validate_input(const unsigned lower_limit, const unsigned upper_limit,
	                    const std::string& description)
{
	unsigned value{};
	std::cout << "Please enter your " << description << " now: ";
	std::cin >> value;
	if (value < lower_limit || value > upper_limit)
	{
		while (value < lower_limit || value > upper_limit)
		{
			std::cout << "invalid " << description << "! Try again: ";
			std::cin >> value;
		}
		std::cin.ignore(32767, '\n');
	}
	return value;
}

unsigned day(const unsigned lower_limit, const unsigned upper_limit)
{
	return validate_input(lower_limit, upper_limit, "day of birth");
}

unsigned month(const unsigned lower_limit, const unsigned upper_limit)
{
	return validate_input(lower_limit, upper_limit, "month of birth");
}

unsigned year(const unsigned lower_limit, const unsigned upper_limit)
{
	return validate_input(lower_limit, upper_limit, "year of birth");
}