/************************************************************
 *
 * Project 4: How Old Are You Really?
 *
 * Author: xx
 * Date: 6 May 2015
 *
 * This is a program designed to calculates the difference 
 * between two dates, which will be expressed in terms of
 * years, months and days.
 *
 ***********************************************************/

#include <bjarne/std_lib_facilities.h>

struct Date {
    int month;
    int day;
    int year;
// Member functions
Date get_date();
Date get_birth_date();
bool is_valid_date(int year, int month, int day);
bool is_before(Date& date1, Date& date2);
Date calculate_age(Date& date1,Date& date2);
};

// Declaration
Date get_date();
Date get_birth_date();
bool is_valid_date(int year, int month, int day);
bool is_before(Date& date1, Date& date2);
Date calculate_age(Date& date1,Date& date2);

int main()
{
    Date date1 = get_date();
    Date date2 = get_birth_date();
    Date get_date();
    // Check if the date is correct
    if (! is_valid_date(year, month, day))
    error("Date is not valid.");
    // Run how old or not?
    char go_on;
    cout << "Would you like to see how old you are (y/n)?\n";
    cin >> go_on;
    if (go_on=='n'){
    cout << "You are so chicken!";
    return 0;}
    else if (go_on!='y')
    error("Please enter y for yes or n for no.");
    Date get_birth_date();
    // Is birthday valid as well?
    if (! is_valid_date(int year, int month, int day))
    error("Date is not valid.");
    // Is the birthday before 'today'?
    if (!(is_before(Date& date1, Date& date2)))
    error("Your birthday should not be later than today, terminator.");
    // Calculate and give the answer.
    Date calculate_age();
}

Date get_date()
{
    Date date1;
    cout << "Welcome to the age calculator!\n";
    cout << "Please enter today's date (mm/dd/yyyy): ";
    int m;
    int d;
    int y;
    // To ignore the '/' during reading
    char slash;
    cin >> m;
    date1.month = m;
    cin >> slash;
    cin >> d;
    date1.day = d;
    cin >> slash;
    cin >> y;
    date1.year = y;
    cout << "Date entered was "<< date1.month << "/" << date1.day << "/" << date1.year <<"\n";
}

Date get_birth_date()
{
    Date date2;
    cout << "Please enter your birth date (mm/dd/yyyy): "; 
    int m;
    int d;
    int y;
    // To ignore the '/' during reading
    char slash;
    cin >> m;
    date2.month = m;
    cin >> slash;
    cin >> d;
    date2.day = d;
    cin >> slash;
    cin >> y;
    date2.year = y;
    cout << "Your birthday is "<< date2.month << "/" << date2.day << "/" << date2.year <<"\n";
}

// Is date valid?
bool is_vaild_date(int year, int month, int day)
{
    if (day<0)
    return false;
    if (month<1 || month>12)
    return false;
    // Check if the date exists or not considering there are have
    // different days when month varies
    int days_in_month=31;
    switch (month){
    case 2:
    days_in_month=28;
    break;
    case 4: case 6: case 9: case 11:
    days_in_month=30;
    break;
    }
    if (days_in_month<day)
    return false;
    return true;
}

//Date check - is birthday before 'today'?
bool is_before(Date& date1, Date& date2)
{
    if (Date& date1.year<Date& date2.year)
    return false;
    else if (Date& date1.month<Date& date2.month)
    return false;
    else if (Date& date1.day< Date& date2.day)
    return false;
    return true;
}

// Calculation
Date calculate_age(Date& date1,Date& date2)
{
    Date date3;
    date3.day = date1.day - date2.day;
    date3.month = date1.month - date2.month;
    date3.year = date1.year - date2.month;
    if (date3.day<0){
        date3.day = 30 + date3.day;
        date3.month = date3.month - 1;
    }
    if (date3.month<0){
        date3.month = 12 + date3.day;
        date3.year = date3.year - 1;
    }
    cout <<"You are " << date3.year <<" years, "<< date3.month <<" months, and " << date3.day <<" days old.\n";
}

    if (day<0)
    return false;
    if (month<1 || month>12)
    return false;