Remove dependency on PHP's ext/calendar extension, and use our own

1 files changed, 179 insertions, 0 deletions

diff --git a/library/fisharebest/ext-calendar/src/JulianCalendar.php b/library/fisharebest/ext-calendar/src/JulianCalendar.php
new file mode 100644
index 0000000000..c74e82cda2
--- /dev/null
+++ b/library/fisharebest/ext-calendar/src/JulianCalendar.php
@@ -0,0 +1,179 @@
+<?php
+namespace Fisharebest\ExtCalendar;
+
+/**
+ * class JulianCalendar - calculations for the Julian calendar.
+ *
+ * @author    Greg Roach <fisharebest@gmail.com>
+ * @copyright (c) 2014 Greg Roach
+ * @license   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/>.
+ */
+class JulianCalendar extends Calendar implements CalendarInterface {
+	/** Same as PHP’s ext/calendar extension */
+	const PHP_CALENDAR_NAME = 'Julian';
+
+	/** Same as PHP’s ext/calendar extension */
+	const PHP_CALENDAR_NUMBER = 1;
+
+	/** Same as PHP’s ext/calendar extension */
+	const PHP_CALENDAR_SYMBOL = 'CAL_JULIAN';
+
+	/** See the GEDCOM specification */
+	const GEDCOM_CALENDAR_ESCAPE = '@#DJULIAN@';
+
+	/**
+	 * Month lengths for regular years and leap-years.
+	 *
+	 * @var int[][]
+	 */
+	protected static $DAYS_IN_MONTH = array(
+		0 => array(1 => 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31),
+		1 => array(1 => 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31),
+	);
+
+	/**
+	 * English month names.
+	 *
+	 * @return string[]
+	 */
+	public function monthNames() {
+		return array(
+			1 => 'January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December',
+		);
+	}
+
+	/**
+	 * Abbreviated English month names.
+	 *
+	 * @return string[]
+	 */
+	public function monthNamesAbbreviated() {
+		return array(
+			1 => 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec',
+		);
+	}
+
+
+	/**
+	 * Determine whether a year is a leap year.
+	 *
+	 * @param  int  $year
+	 * @return bool
+	 */
+	public function leapYear($year) {
+		if ($year < 0) {
+			$year++;
+		}
+
+		return $year % 4 == 0;
+	}
+
+	/**
+	 * Convert a Julian day number into a year/month/day.
+	 *
+	 * @param $jd
+	 *
+	 * @return int[];
+	 */
+	public function jdToYmd($jd) {
+		$c = $jd + 32082;
+		$d = (int)((4 * $c + 3) / 1461);
+		$e = $c - (int)(1461 * $d / 4);
+		$m = (int)((5 * $e + 2) / 153);
+		$day = $e - (int)((153 * $m + 2) / 5) + 1;
+		$month = $m + 3 - 12 * (int)($m / 10);
+		$year = $d - 4800 + (int)($m / 10);
+		if ($year < 1) {
+			// 0=1BC, -1=2BC, etc.
+			$year--;
+		}
+
+		return array($year, $month, $day);
+	}
+
+	/**
+	 * Convert a year/month/day into a Julian day number
+	 *
+	 * @param int $year
+	 * @param int $month
+	 * @param int $day
+	 *
+	 * @return int
+	 */
+	public function ymdToJd($year, $month, $day) {
+		if ($year < 0) {
+			// 1 B.C.E. => 0, 2 B.C.E> => 1, etc.
+			++$year;
+		}
+		$a = (int)((14 - $month) / 12);
+		$year = $year + 4800 - $a;
+		$month = $month + 12 * $a - 3;
+
+		return $day + (int)((153 * $month + 2) / 5) + 365 * $year + (int)($year / 4) - 32083;
+	}
+
+	/**
+	 * Calculate the number of days in a month.
+	 *
+	 * @param  int $year
+	 * @param  int $month
+	 *
+	 * @return int
+	 */
+	public function daysInMonth($year, $month) {
+		if ($year == 0 || $month < 1 || $month > 12) {
+			return trigger_error('invalid date.', E_USER_WARNING);
+		} else {
+			return static::$DAYS_IN_MONTH[$this->leapYear($year)][$month];
+		}
+	}
+
+	/**
+	 * Get the number of days after March 21 that easter falls, for a given year.
+	 *
+	 * Uses the algorithm found in PHP’s ext/calendar/easter.c
+	 *
+	 * @param int $year
+	 *
+	 * @return int
+	 */
+	public function easterDays($year) {
+		// The “golden” number
+		$golden = 1 + $year % 19;
+
+		// The “dominical” number (finding a Sunday)
+		$dom = ($year + (int)($year / 4) + 5) % 7;
+		if ($dom < 0) {
+			$dom += 7;
+		}
+
+		// The uncorrected “Paschal full moon” date
+		$pfm = (3 - 11 * $golden - 7) % 30;
+		if ($pfm < 0) {
+			$pfm += 30;
+		}
+
+		// The corrected “Paschal full moon” date
+		if ($pfm == 29 || $pfm == 28 && $golden > 11) {
+			$pfm--;
+		}
+
+		$tmp = (4 - $pfm - $dom) % 7;
+		if ($tmp < 0) {
+			$tmp += 7;
+		}
+
+		return $pfm + $tmp + 1;
+	}
+}