Added handle_maybe function (#2)

Author: Nicolò Pignatelli

src/Maybe/functions.php

@@ -42,3 +42,23 @@ public function ifSome(callable $f): Maybe
         }
     };
 }
+
+/**
+ * @template T
+ * @template U
+ * @template W
+ * @psalm-param Maybe<T> $maybe
+ * @psalm-param callable(T):U $someHandler
+ * @psalm-param callable():W $noneHandler
+ * @psalm-return U|W
+ */
+function handle_maybe(Maybe $maybe, callable $someHandler, callable $noneHandler) {
+    switch (true) {
+        case $maybe instanceof Some:
+            return $someHandler($maybe->extract());
+        case $maybe instanceof None:
+            return $noneHandler();
+        default:
+            throw new \LogicException(sprintf('Unknown maybe type %s', get_class($maybe)));
+    }
+}

tests/Maybe/FunctionsTest.php

@@ -4,7 +4,9 @@
 
 use Careship\Functional\Maybe\None;
 use Careship\Functional\Maybe\Some;
+use PHPUnit\Framework\MockObject\Rule\InvokedCount as InvokedCountMatcher;
 use PHPUnit\Framework\TestCase;
+use function Careship\Functional\Maybe\handle_maybe;
 use function Careship\Functional\Maybe\none;
 use function Careship\Functional\Maybe\some;
 
@@ -59,4 +61,36 @@ public function none_if_some_is_a_no_op()
             $spy->myMethod();
         });
     }
+
+    /** @test */
+    public function some_handler_is_invoked_in_handle_maybe()
+    {
+        $someSpy = $this->getMockBuilder(\stdClass::class)->addMethods(['spy'])->getMock();
+        $someSpy->expects($this->exactly(1))->method('spy');
+
+        $noneSpy = $this->getMockBuilder(\stdClass::class)->addMethods(['spy'])->getMock();
+        $noneSpy->expects($this->never())->method('spy');
+
+        handle_maybe(
+            some('foo'),
+            [$someSpy, 'spy'],
+            [$noneSpy, 'spy']
+        );
+    }
+
+    /** @test */
+    public function none_handler_is_invoked_in_handle_maybe()
+    {
+        $someSpy = $this->getMockBuilder(\stdClass::class)->addMethods(['spy'])->getMock();
+        $someSpy->expects($this->never())->method('spy');
+
+        $noneSpy = $this->getMockBuilder(\stdClass::class)->addMethods(['spy'])->getMock();
+        $noneSpy->expects($this->exactly(1))->method('spy');
+
+        handle_maybe(
+            none(),
+            [$someSpy, 'spy'],
+            [$noneSpy, 'spy']
+        );
+    }
 }