Add Command->parameters() method to introspect arguments

src/Command.php

@@ -2,6 +2,8 @@
 
 namespace NoccyLabs\React\CommandBus;
 
+use ReflectionFunction;
+use ReflectionNamedType;
 use React\Promise\Deferred;
 use React\Promise\Promise;
 use React\Promise\PromiseInterface;
@@ -38,5 +40,31 @@ class Command
         });
     }
 
+    public function parameters(): array
+    {
+        $refl = new ReflectionFunction($this->handler);
+        $args = [];
+
+        foreach ($refl->getParameters() as $parameter) {
+            $name = $parameter->getName();
+            $type = null;
+            if (!$parameter->hasType()) {
+                $type = 'any';
+            } else {
+                $type = $parameter->getType();
+                if ($type instanceof ReflectionNamedType && $type->isBuiltin()) {
+                    $type = $type->getName();
+                } else {
+                    $type = null;
+                }
+            }
+            
+            if ($parameter->isOptional()) $type = "?{$type}";
+            if ($type !== null) $args[$name] = $type;
+        }
+
+        return $args;
+    }
+
 }