+/*
+ * Copyright (C) 2012 Andy Spencer <andy753421@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* Time Keeping Bugs Abound! */
+
+#include <stdio.h>
+#include <time.h>
+
+#include "date.h"
+
+/* Global data */
+year_t YEAR;
+month_t MONTH;
+day_t DAY;
+
+/* Initialize */
+void date_init(void)
+{
+ time_t sec = time(NULL);
+ struct tm *tm = localtime(&sec);
+
+ YEAR = tm->tm_year+1900;
+ MONTH = tm->tm_mon;
+ DAY = tm->tm_mday-1;
+}
+
+/* Time functions */
+int is_leap_year(year_t year)
+{
+ return (year % 400 == 0) ? 1 :
+ (year % 100 == 0) ? 0 :
+ (year % 4 == 0) ? 1 : 0;
+}
+
+int days_in_year(year_t year)
+{
+ return 365 + is_leap_year(year);
+}
+
+int days_in_month(year_t year, month_t month)
+{
+ static int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+ int days = mdays[month];
+ if (month == FEB)
+ days += is_leap_year(year);
+ return days;
+}
+
+int weeks_in_month(year_t year, month_t month)
+{
+ int start = start_of_month(year, month);
+ int days = days_in_month(year, month);
+ return ((start + days)-1) / 7 + 1;
+}
+
+wday_t day_of_week(year_t year, month_t month, day_t day)
+{
+ static int tmp[] = {0, 3, 2, 5, 0, 3,
+ 5, 1, 4, 6, 2, 4};
+ if (month < MAR)
+ year--;
+ int start = year + year / 4
+ - year / 100
+ + year / 400
+ + tmp[month];
+ return (start + day + 1) % 7;
+}
+
+wday_t start_of_month(year_t year, month_t month)
+{
+ return day_of_week(year, month, 0);
+}
+
+void add_days(year_t *year, month_t *month, day_t *day, int days)
+{
+ time_t time = mktime(&(struct tm){
+ .tm_year = *year-1900,
+ .tm_mon = *month,
+ .tm_mday = *day+1,
+ .tm_hour = 12});
+ time += days*24*60*60;
+ struct tm *tm = localtime(&time);
+ *year = tm->tm_year+1900;
+ *month = tm->tm_mon;
+ *day = tm->tm_mday-1;
+}
+
+void add_months(year_t *year, month_t *month, int months)
+{
+ int total = *year*12 + *month + months;
+ *year = total / 12;
+ *month = total % 12;
+}
+
+/* Debug functions */
+const char *month_to_str(month_t month)
+{
+ static const char *map[] =
+ { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+ "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", };
+ return map[month%12];
+}
+const char *month_to_string(month_t month)
+{
+ static const char *map[] =
+ { "January", "February", "March", "April",
+ "May", "June", "July", "August",
+ "September", "October", "November", "December" };
+ return map[month%12];
+}
+
+const char *day_to_st(wday_t day)
+{
+ static const char *map[] =
+ { "Su","Mo", "Tu", "We", "Th", "Fr", "Sa" };
+ return map[day%7];
+}
+const char *day_to_str(wday_t day)
+{
+ static const char *map[] =
+ { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
+ return map[day%7];
+}
+const char *day_to_string(wday_t day)
+{
+ static const char *map[] =
+ { "Sunday", "Monday", "Tuesday", "Wednesday",
+ "Thursday", "Friday", "Saturday" };
+ return map[day%7];
+}
+
+/* Test functions */
+void test_time(void)
+{
+ printf("Info\n");
+ printf(" Year Month Start Weeks Days\n");
+ for (int y = 2012; y <= 2012; y++)
+ for (int m = JAN; m <= DEC; m++) {
+ printf(" %-5d", y);
+ printf(" %-10s", month_to_string(m));
+ printf(" %-6s", day_to_str(start_of_month(y,m)));
+ printf(" %-6d", weeks_in_month(y,m));
+ printf(" %-2d", days_in_month(y,m));
+ printf("\n");
+ }
+}