Refactoring for Release 2.0.0

.gitignore

@@ -7,3 +7,6 @@ createPhar
 createPhar.asc
 composer.lock
 phpunit.xml
+/.phpunit.cache/
+/.php-cs-fixer.cache
+/.phpunit.result.cache

src/EmperorNortonCommands/lib/DateTimeFactory.php

@@ -0,0 +1,62 @@
+<?php
+/**
+ * This file is part of the Emperor Norton Commands.
+ *
+ * Public domain. All rites reversed.
+ */
+
+declare(strict_types=1);
+
+namespace EmperorNortonCommands\lib;
+
+use DateTimeImmutable;
+use DateTimeZone;
+use InvalidArgumentException;
+
+/**
+ * @package EmperorNortonCommands\lib\Ddate
+ * @internal
+ */
+final class DateTimeFactory
+{
+    /**
+     * @throws InvalidArgumentException if value is not a valid Gregorian date
+     */
+    public static function createFromStringOrNull(string|null $value): DateTimeImmutable
+    {
+        if ($value === null) {
+            return new DateTimeImmutable();
+        }
+        if (!is_numeric($value) && 8 !== strlen($value)) {
+            self::throwInvalidArgumentException($value, 'string is not numeric or given length is not 8 characters');
+        }
+        $day = (int)substr($value, 0, 2);
+        $month = (int)substr($value, 2, 2);
+        $year = (int)substr($value, 4, 4);
+        if (!checkdate($month, $day, $year)) {
+            self::throwInvalidArgumentException($value, 'is not a valid Gregorian date');
+        }
+        $result = DateTimeImmutable::createFromFormat(
+                format: 'j-n-Y-H:i:s',
+                datetime: sprintf('%1$d-%2$d-%3$d-00:00:00', $day, $month, $year),
+                timezone: new DateTimeZone('UTC')
+            );
+        assert($result !== false);
+
+        return $result;
+    }
+
+    /**
+     * @throws InvalidArgumentException
+     */
+    private static function throwInvalidArgumentException(string $value, string $additionalInfo): void
+    {
+        throw new InvalidArgumentException(
+            sprintf(
+                'Given date value expected to be string (format dmY) or null, found "%1$s": %2$s',
+                $value,
+                $additionalInfo,
+            )
+        );
+    }
+}