expression language: inject an object providing helper functions/methods

instead of injecting global functions inject an object. Mainly to have some namespacing in case the official language gains new functions and to make it clear which function are from us and where the documentation for thenm needs to be looked up.

src/ExpressionLanguage/ExpressionExtension.php

+<?php
+
+declare(strict_types=1);
+
+namespace Dbp\Relay\CoreBundle\ExpressionLanguage;
+
+/**
+ * This Type gets injected into our expression language variant with the name
+ * 'relay'. This allows us to add functions/methods with some kind of namespacing,
+ * instead of polluting the global namespace.
+ */
+class ExpressionExtension
+{
+    /**
+     * @var ExpressionLanguage
+     */
+    private $lang;
+
+    public function __construct(ExpressionLanguage $lang)
+    {
+        $this->lang = $lang;
+    }
+
+    public static function str_starts_with()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('str_starts_with', $args);
+    }
+
+    public static function str_ends_with()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('str_ends_with', $args);
+    }
+
+    public static function substr()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('substr', $args);
+    }
+
+    public static function strpos()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('strpos', $args);
+    }
+
+    public static function strlen()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('strlen', $args);
+    }
+
+    public static function ceil()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('ceil', $args);
+    }
+
+    public static function floor()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('floor', $args);
+    }
+
+    public static function round()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('round', $args);
+    }
+
+    public static function max()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('max', $args);
+    }
+
+    public static function min()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('min', $args);
+    }
+
+    public static function count()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('count', $args);
+    }
+
+    public static function implode()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('implode', $args);
+    }
+
+    public static function explode()
+    {
+        $args = func_get_args();
+
+        return call_user_func_array('explode', $args);
+    }
+
+    public static function empty($value): bool
+    {
+        // empty is not a real function, so call_user_func_array doesn't work
+        return empty($value);
+    }
+
+    public function map(iterable $iterable, string $expression): array
+    {
+        $transformedResult = [];
+        foreach ($iterable as $key => $value) {
+            $transformedResult[$key] = $this->lang->evaluate($expression, ['key' => $key, 'value' => $value, 'relay' => $this]);
+        }
+
+        return $transformedResult;
+    }
+
+    public function filter(iterable $iterable, string $expression): array
+    {
+        $filteredResult = [];
+        foreach ($iterable as $key => $value) {
+            if ($this->lang->evaluate($expression, ['key' => $key, 'value' => $value])) {
+                $filteredResult[] = $value;
+            }
+        }
+
+        return $filteredResult;
+    }
+
+    public static function isNullOrEmpty($value)
+    {
+        return $value === null || $value === '';
+    }
+}