/* 
 * Program that finds Julian date for given month, day, year.
 *
 * Prompts for month, day, year.
 */
#include <stdio.h>
#include <stdbool.h>
#include <string.h>

int jdate(char *mname, int day, bool is_leap);

int main(int argc, char *argv[]) {

	char mname[4];
	int day, year;
	puts("enter month (3 char) day year");
	if (scanf("%3s %d %d", mname, &day, &year) != 3) {
		puts("invalid input");
		return 1;
	}
	if ((year < 1) || (day < 1)) {
		puts("invalid input");
		return 1;
	}

	bool is_leapyear = 
		((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0)));

	/*
	 * compute julian day and then echo input, followed by
	 * "invalid input" or converted day
	 */
	int jday = jdate(mname, day, is_leapyear);

	printf("%s %d %d (%s) ", /* print this for both valid/invalid input */
		mname, day, year,
		(is_leapyear) ? "a leapyear" : "not a leapyear");
	if (jday == -1) {
		puts("is invalid");
		return 1;
	}
	else {
		printf("is Julian date %d\n", jday);
		return 0;
	}
}

/* type for table of entries, one per month */

typedef struct {
	char *mname;
	int days_in_month;
	int extra_days_for_leapyear;
} month_and_days_t;

/* return julian day, or -1 if input is invalid */
int jdate(char *mname, int day, bool is_leap) {

	month_and_days_t cal[] = {
		{ "Jan", 31, 0 },
		{ "Feb", 28, 1 },
		{ "Mar", 31, 0 },
		{ "Apr", 30, 0 },
		{ "May", 31, 0 },
		{ "Jun", 30, 0 },
		{ "Jul", 31, 0 },
		{ "Aug", 31, 0 },
		{ "Sep", 30, 0 },
		{ "Oct", 31, 0 },
		{ "Nov", 30, 0 },
		{ "Dec", 31, 0 }
	};

	int days_prev = 0; /* days in previous months */
	for (int i = 0; i < 12; ++i) {
		if (strcmp(mname, cal[i].mname) == 0) {
			if (day > cal[i].days_in_month) {
				return -1;
			}
			return days_prev + day;
		}
		else {
			days_prev += cal[i].days_in_month;
			if (is_leap)
				days_prev += cal[i].extra_days_for_leapyear;
		}
	}
	return -1;
}