allow fluent functions registration

resolves #3

src/FluentTranslator.php

@@ -2,19 +2,24 @@
 
 namespace Major\Fluent\Laravel;
 
+use Closure;
 use Countable;
 use Illuminate\Contracts\Translation\Loader;
 use Illuminate\Contracts\Translation\Translator as TranslatorContract;
 use Illuminate\Filesystem\Filesystem;
 use Illuminate\Translation\MessageSelector;
 use Illuminate\Translation\Translator as BaseTranslator;
 use Major\Fluent\Bundle\FluentBundle;
+use Major\Fluent\Exceptions\Bundle\FunctionExistsException;
 
 final class FluentTranslator implements TranslatorContract
 {
     /** @var array<string, array<string, FluentBundle|false>> */
     private array $loaded = [];
 
+    /** @var array<string, Closure> */
+    private array $functions = [];
+
     public function __construct(
         protected BaseTranslator $baseTranslator,
         protected Filesystem $files,
@@ -62,6 +67,23 @@ public function get($key, array $replace = [], $locale = null, bool $fallback =
         return $message ?? $this->baseTranslator->get(...func_get_args());
     }
 
+    public function addFunction(string $name, Closure $function): void
+    {
+        if (array_key_exists($name, $this->functions)) {
+            throw new FunctionExistsException($name);
+        }
+
+        $this->functions[$name] = $function;
+
+        foreach ($this->loaded as $locale) {
+            foreach ($locale as $bundle) {
+                if ($bundle !== false) {
+                    $bundle->addFunction($name, $function);
+                }
+            }
+        }
+    }
+
     private function getBundle(string $locale, string $group): ?FluentBundle
     {
         if (! isset($this->loaded[$locale][$group])) {
@@ -80,7 +102,8 @@ private function loadFtl(string $locale, string $group): ?FluentBundle
         }
 
         return (new FluentBundle($locale, ...$this->bundleOptions))
-            ->addFtl($this->files->get($path));
+            ->addFtl($this->files->get($path))
+            ->addFunctions($this->functions);
     }
 
     /**

tests/FunctionsTest.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace Major\Fluent\Laravel\Tests;
+
+use Major\Fluent\Exceptions\Bundle\FunctionExistsException;
+use Major\Fluent\Exceptions\Resolver\ReferenceException;
+
+final class FunctionsTest extends TestCase
+{
+    /**
+     * @testdox function can be used
+     */
+    public function testUsage(): void
+    {
+        $this->translator->addFunction('CONCAT', fn (string ...$args) => implode($args));
+
+        $this->assertSame('FooBar', __('functions.strings'));
+    }
+
+    /**
+     * @testdox arguments can be passed to function
+     */
+    public function testArguments(): void
+    {
+        $this->translator->addFunction('CONCAT', fn (string ...$args) => implode($args));
+
+        $this->assertSame('BarBaz', __('functions.args', ['foo' => 'Bar', 'bar' => 'Baz']));
+    }
+
+    /**
+     * @testdox function can not be registered twice
+     */
+    public function testRegisterTwice(): void
+    {
+        $this->expectException(FunctionExistsException::class);
+        $this->expectExceptionMessage('Attempt to override an existing function: CONCAT().');
+
+        $this->translator->addFunction('CONCAT', fn (string ...$args) => implode($args));
+        $this->translator->addFunction('CONCAT', fn (string ...$args) => implode(', ', $args));
+    }
+
+    /**
+     * @testdox function can be registered after bundle is resolved
+     */
+    public function testLateRegistration(): void
+    {
+        try {
+            $this->assertSame('FooBar', __('functions.strings'));
+
+            $this->fail('Exception should have been thrown.');
+        } catch (ReferenceException $e) {
+            $this->assertSame('Unknown function: CONCAT().', $e->getMessage());
+        }
+
+        $this->translator->addFunction('CONCAT', fn (string ...$args) => implode($args));
+
+        $this->assertSame('FooBar', __('functions.strings'));
+    }
+}

tests/lang/pl/functions.ftl

@@ -0,0 +1,2 @@
+strings = { CONCAT("Foo", "Bar") }
+args = { CONCAT($foo, $bar) }