/*
    person.c
    Jeff Ondich, 5 March 2022

    A program to help us investigate how struct types
    are passed as parameters.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdbool.h>

#define MAX_NAME_LENGTH 32

typedef struct {
    char name[MAX_NAME_LENGTH];
    int birth_year;
    int birth_month;
    int birth_day;
} person_t;

person_t create_person(char *name, int year, int month, int day) {
    person_t person;
    person.birth_year = year;
    person.birth_month = month;
    person.birth_day = day;
    if (name != NULL) {
        strncpy(person.name, name, MAX_NAME_LENGTH);
        person.name[MAX_NAME_LENGTH - 1] = '\0';
    }

    return person;
}

// Returns true if person1 is (strictly) older than person2, false otherwise.
int is_older(person_t person1, person_t person2) {
    // What happens if we uncomment this?
    // strcpy(person1.name, "Friedrich Schiller");

    if (person1.birth_year != person2.birth_year) {
        return person1.birth_year < person2.birth_year;
    }

    if (person1.birth_month != person2.birth_month) {
        return person1.birth_month < person2.birth_month;
    }

    return person1.birth_day < person2.birth_day;
} 

// Returns the specified person's age in whole years on the specified date.
// Returns -1 if the person's birthdate is after the specified date.
int age(person_t person, int year, int month, int day) {
    bool date_is_before_birthday =
        (month < person.birth_month) || (month == person.birth_month && day < person.birth_day);

    if (year < person.birth_year || (year == person.birth_year && date_is_before_birthday)) {
        return -1;
    }

    int years = year - person.birth_year;
    if (date_is_before_birthday) {
        years--;
    }

    return years;
} 

void person_test() {
    person_t p1;
    p1 = create_person("Alan Turing", 1912, 6, 23);
    int age1 = age(p1, 2022, 3, 7);
    printf("%s is %d years old today\n", p1.name, age1);

    person_t p2;
    p2 = create_person("John von Neumann", 1903, 12, 28); 
    int age2 = age(p2, 2022, 3, 7);
    printf("%s is %d years old today\n", p2.name, age2);

    if (is_older(p1, p2)) {
        printf("%s is older than %s\n", p1.name, p2.name);
    } else {
        printf("%s is older than %s\n", p2.name, p1.name);
    }
}

int main() {
    person_test();
    return 0;
}