share apply dispatch with compiled fixed functions

src/Utils/FixedFunction.php

@@ -11,10 +11,10 @@ namespace Kadet\Functional\Utils;
 
 
 use function Kadet\Functional\apply;
+use function Kadet\Functional\applyWithArity;
 use Kadet\Functional\Compilable;
 use function Kadet\Functional\compile;
 use Kadet\Functional\Decorator;
-use function Kadet\Functional\partial;
 use function Kadet\Functional\reflect;
 
 class FixedFunction implements Decorator, Compilable
@@ -70,22 +70,7 @@ class FixedFunction implements Decorator, Compilable
         $call = $fixed instanceof CurriedFunction ? $fixed : compile($fixed);
 
         $self = static function (...$args) use (&$self, $fixed, $call, $variadic, $required, $all) {
-            array_unshift($args, $self);
-
-            switch (true) {
-                case $variadic:
-                    return partial($fixed, ...$args);
-
-                case count($args) >= $all:
-                    $applied = $call(...array_slice($args, 0, $all));
-                    return is_callable($applied) ? apply($applied, ...array_slice($args, $all)) : $applied;
-
-                case count($args) >= $required:
-                    return $call(...$args);
-
-                default:
-                    return partial($fixed, ...$args);
-            }
+            return applyWithArity($fixed, $call, $variadic, $required, $all, [$self, ...$args]);
         };
 
         return $self;

src/Utils/index.php

@@ -24,29 +24,45 @@ function apply(callable $callable, ...$args)
 {
     try {
         $reflection = reflect($callable);
-        $required   = $reflection->getNumberOfRequiredParameters();
-        $all        = $reflection->getNumberOfParameters();
 
-        switch (true) {
-            case $reflection->isVariadic():
-                return partial($callable, ...$args);
-
-            case count($args) >= $all:
-                $applied = $callable(...array_slice($args, 0, $all));
-                return is_callable($applied) ? apply($applied, ...array_slice($args, $all)) : $applied;
-
-            case count($args) >= $required:
-                return $callable(...$args);
-
-            default:
-                return partial($callable, ...$args);
-        }
+        return applyWithArity(
+            $callable,
+            $callable,
+            $reflection->isVariadic(),
+            $reflection->getNumberOfRequiredParameters(),
+            $reflection->getNumberOfParameters(),
+            $args
+        );
     } catch (\ReflectionException $exception) {
         // if cannot gather necessary information for intelligent application just use normal one
         return $callable(...$args);
     }
 }
 
+/**
+ * The argument dispatch of apply(), with the arity of $callable already known: it calls $call when there are enough
+ * arguments and partially applies $callable otherwise.
+ *
+ * @internal
+ */
+function applyWithArity(callable $callable, callable $call, bool $variadic, int $required, int $all, array $args)
+{
+    switch (true) {
+        case $variadic:
+            return partial($callable, ...$args);
+
+        case count($args) >= $all:
+            $applied = $call(...array_slice($args, 0, $all));
+            return is_callable($applied) ? apply($applied, ...array_slice($args, $all)) : $applied;
+
+        case count($args) >= $required:
+            return $call(...$args);
+
+        default:
+            return partial($callable, ...$args);
+    }
+}
+
 function curry(callable $callable, ?int $threshold = null, ...$args): CurriedFunction
 {
     return new CurriedFunction($callable, $threshold, ...$args);