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src/Helpers/TrinaryLogicHelper.php

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+<?php
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2023 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+declare(strict_types=1);
+
+
+namespace App\Helpers;
+
+/**
+ * Helper functions for logic operations with trinary logic.
+ * True and false are represented as classical boolean values, undefined is represented as null.
+ */
+class TrinaryLogicHelper
+{
+
+    /**
+     * Implements the trinary logic NOT.
+     * @param  bool|null  $a
+     * @return bool|null
+     */
+    public static function not(?bool $a): ?bool
+    {
+        if ($a === null) {
+            return null;
+        }
+        return !$a;
+    }
+
+
+    /**
+     * Returns the trinary logic OR of the given parameters. At least one parameter is required.
+     * @param  bool|null  ...$args
+     * @return bool|null
+     */
+    public static function or(?bool ...$args): ?bool
+    {
+        if (count($args) === 0) {
+            throw new \LogicException('At least one parameter is required.');
+        }
+
+        // The trinary or is the maximum of the integer representation of the parameters.
+        return self::intToBool(
+            max(array_map(self::boolToInt(...), $args))
+        );
+    }
+
+    /**
+     * Returns the trinary logic AND of the given parameters. At least one parameter is required.
+     * @param  bool|null  ...$args
+     * @return bool|null
+     */
+    public static function and(?bool ...$args): ?bool
+    {
+        if (count($args) === 0) {
+            throw new \LogicException('At least one parameter is required.');
+        }
+
+        // The trinary and is the minimum of the integer representation of the parameters.
+        return self::intToBool(
+            min(array_map(self::boolToInt(...), $args))
+        );
+    }
+
+    /**
+     * Convert the trinary bool to an integer, where true is 1, false is -1 and null is 0.
+     * @param  bool|null  $a
+     * @return int
+     */
+    private static function boolToInt(?bool $a): int
+    {
+        if ($a === null) {
+            return 0;
+        }
+        return $a ? 1 : -1;
+    }
+
+    /**
+     * Convert the integer to a trinary bool, where 1 is true, -1 is false and 0 is null.
+     * @param  int  $a
+     * @return bool|null
+     */
+    private static function intToBool(int $a): ?bool
+    {
+        if ($a === 0) {
+            return null;
+        }
+        return $a > 0;
+    }
+}