Initial commit

api/includes/CzechHolidays.php

@@ -0,0 +1,117 @@
+<?php
+
+/**
+ * Czech Holidays & Work Fund Calculator
+ *
+ * Provides Czech public holidays (including movable Easter dates)
+ * and monthly work fund calculations.
+ */
+
+declare(strict_types=1);
+
+class CzechHolidays
+{
+    /** @var array<int, list<string>> Static cache for holidays by year */
+    private static array $holidayCache = [];
+
+    /**
+     * Get all Czech public holidays for a given year.
+     * Returns array of 'Y-m-d' strings (11 fixed + 2 Easter-based).
+     * Results are cached per-request to avoid recalculation.
+     *
+     * @return list<string>
+     */
+    public static function getHolidays(int $year): array
+    {
+        if (isset(self::$holidayCache[$year])) {
+            return self::$holidayCache[$year];
+        }
+        // Fixed holidays
+        $holidays = [
+            sprintf('%04d-01-01', $year), // Den obnovy samostatného českého státu
+            sprintf('%04d-05-01', $year), // Svátek práce
+            sprintf('%04d-05-08', $year), // Den vítězství
+            sprintf('%04d-07-05', $year), // Den slovanských věrozvěstů Cyrila a Metoděje
+            sprintf('%04d-07-06', $year), // Den upálení mistra Jana Husa
+            sprintf('%04d-09-28', $year), // Den české státnosti
+            sprintf('%04d-10-28', $year), // Den vzniku samostatného československého státu
+            sprintf('%04d-11-17', $year), // Den boje za svobodu a demokracii
+            sprintf('%04d-12-24', $year), // Štědrý den
+            sprintf('%04d-12-25', $year), // 1. svátek vánoční
+            sprintf('%04d-12-26', $year), // 2. svátek vánoční
+        ];
+
+        // Easter-based holidays (Anonymous Gregorian algorithm)
+        $easterSunday = self::getEasterSunday($year);
+        $goodFriday = date('Y-m-d', strtotime($easterSunday . ' -2 days'));
+        $easterMonday = date('Y-m-d', strtotime($easterSunday . ' +1 day'));
+        $holidays[] = $goodFriday;     // Velký pátek
+        $holidays[] = $easterMonday;    // Velikonoční pondělí
+
+        sort($holidays);
+        self::$holidayCache[$year] = $holidays;
+        return $holidays;
+    }
+
+    /**
+     * Check if a date is a Czech public holiday.
+     */
+    public static function isHoliday(string $date): bool
+    {
+        $year = (int)date('Y', strtotime($date));
+        $formatted = date('Y-m-d', strtotime($date));
+        return in_array($formatted, self::getHolidays($year), true);
+    }
+
+    /**
+     * Get number of business days (Mon-Fri, excluding holidays) in a month.
+     */
+    public static function getBusinessDaysInMonth(int $year, int $month): int
+    {
+        $holidays = self::getHolidays($year);
+        $daysInMonth = cal_days_in_month(CAL_GREGORIAN, $month, $year);
+        $businessDays = 0;
+
+        for ($day = 1; $day <= $daysInMonth; $day++) {
+            $date = sprintf('%04d-%02d-%02d', $year, $month, $day);
+            $dayOfWeek = (int)date('N', strtotime($date)); // 1=Mon, 7=Sun
+            if ($dayOfWeek <= 5 && !in_array($date, $holidays, true)) {
+                $businessDays++;
+            }
+        }
+
+        return $businessDays;
+    }
+
+    /**
+     * Get monthly work fund in hours (business days × 8).
+     */
+    public static function getMonthlyWorkFund(int $year, int $month): float
+    {
+        return self::getBusinessDaysInMonth($year, $month) * 8.0;
+    }
+
+    /**
+     * Calculate Easter Sunday date using the Anonymous Gregorian algorithm.
+     * Returns 'Y-m-d' string.
+     */
+    private static function getEasterSunday(int $year): string
+    {
+        $a = $year % 19;
+        $b = intdiv($year, 100);
+        $c = $year % 100;
+        $d = intdiv($b, 4);
+        $e = $b % 4;
+        $f = intdiv($b + 8, 25);
+        $g = intdiv($b - $f + 1, 3);
+        $h = (19 * $a + $b - $d - $g + 15) % 30;
+        $i = intdiv($c, 4);
+        $k = $c % 4;
+        $l = (32 + 2 * $e + 2 * $i - $h - $k) % 7;
+        $m = intdiv($a + 11 * $h + 22 * $l, 451);
+        $month = intdiv($h + $l - 7 * $m + 114, 31);
+        $day = (($h + $l - 7 * $m + 114) % 31) + 1;
+
+        return sprintf('%04d-%02d-%02d', $year, $month, $day);
+    }
+}