add pipeline

src/Utils/FunctionPipeline.php

@@ -0,0 +1,48 @@
+<?php
+/**
+ * Copyright 2018 Kacper Donat
+ *
+ * @author Kacper "Kadet" Donat <kacper@kadet.net>
+ *
+ * Full license available in separate LICENSE file
+ */
+
+namespace Kadet\Functional\Utils;
+
+
+class FunctionPipeline
+{
+    /**
+     * @var callable[]
+     */
+    private $functions = [];
+
+    /**
+     * FunctionPipeline constructor.
+     *
+     * @param callable[] $functions
+     */
+    public function __construct(callable ...$functions)
+    {
+        $this->functions = $functions;
+    }
+
+    public function append(callable $callable)
+    {
+        return new static(...array_merge($this->functions, [ $callable ]));
+    }
+
+    public function prepend(callable $callable)
+    {
+        return new static($callable, ...$this->functions);
+    }
+
+    public function __invoke(...$args)
+    {
+        return array_reduce($this->functions, function ($arg, $callable) {
+            return $arg instanceof UnpackedArgs
+                ? $callable(...$arg->getArrayCopy())
+                : $callable($arg);
+        }, new UnpackedArgs($args));
+    }
+}

src/Utils/UnpackedArgs.php

@@ -0,0 +1,13 @@
+<?php
+/**
+ * Copyright 2018 Kacper Donat
+ *
+ * @author Kacper "Kadet" Donat <kacper@kadet.net>
+ *
+ * Full license available in separate LICENSE file
+ */
+
+namespace Kadet\Functional\Utils;
+
+
+class UnpackedArgs extends \ArrayObject { }

src/Utils/index.php

@@ -10,6 +10,7 @@
 namespace Kadet\Functional;
 
 use Kadet\Functional\Utils\CurriedFunction;
+use Kadet\Functional\Utils\FunctionPipeline;
 use Kadet\Functional\Utils\PartiallyAppliedFunction;
 
 function partial(callable $callable, ...$args): PartiallyAppliedFunction
@@ -25,4 +26,9 @@ function curry(callable $callable, int $threshold = null, ...$args): CurriedFunc
 function uncurry(CurriedFunction $curried)
 {
     return $curried->uncurry();
-}
+}
+
+function pipe(...$functions)
+{
+    return new FunctionPipeline(...$functions);
+}

src/functions.php

@@ -78,4 +78,4 @@ function reflect(callable $callable): \ReflectionFunctionAbstract
     }
 }
 
-define(__NAMESPACE__.'\\_', symbol());
+define(__NAMESPACE__.'\\_', symbol('placeholder'));

tests/FunctionPipelineTest.php

@@ -0,0 +1,95 @@
+<?php
+/**
+ * Copyright 2018 Kacper Donat
+ *
+ * @author Kacper "Kadet" Donat <kacper@kadet.net>
+ *
+ * Full license available in separate LICENSE file
+ */
+
+use \Kadet\Functional as f;
+
+class FunctionPipelineTest extends \PHPUnit\Framework\TestCase
+{
+    /** @var \PHPUnit\Framework\MockObject\MockObject */
+    private $mock;
+
+    protected function setUp()/* The :void return type declaration that should be here would cause a BC issue */
+    {
+        $this->mock = $this
+            ->getMockBuilder('stdClass')
+            ->setMethods(['a', 'b', 'c'])
+            ->getMock();
+    }
+
+    public function testPipelineCalling()
+    {
+        $pipeline = f\pipe(
+            [$this->mock, 'a'],
+            [$this->mock, 'b']
+        );
+
+        $this->mock->method('a')->willReturn('b');
+        $this->mock->method('b')->willReturn('c');
+
+        $this->mock->expects($this->once())->method('a')->with('a');
+        $this->mock->expects($this->once())->method('b')->with('b');
+
+        $this->assertSame('c', $pipeline('a'));
+    }
+
+    public function testPipelineForward()
+    {
+        $pipeline = f\pipe(
+            [$this->mock, 'a']
+        );
+
+        $this->mock->method('a')->willReturn('b');
+
+        $this->mock->expects($this->once())->method('a')->with('a');
+
+        $this->assertSame('b', $pipeline('a'));
+    }
+
+    public function testPipelineAppend()
+    {
+        $pipeline = f\pipe(
+            [$this->mock, 'a'],
+            [$this->mock, 'b']
+        );
+
+        $second = $pipeline->append([$this->mock, 'c']);
+
+        $this->mock->method('a')->willReturn('b');
+        $this->mock->method('b')->willReturn('c');
+        $this->mock->method('c')->willReturn('d');
+
+        $this->mock->expects($this->exactly(2))->method('a')->with('a');
+        $this->mock->expects($this->exactly(2))->method('b')->with('b');
+        $this->mock->expects($this->once())->method('c')->with('c');
+
+        $this->assertSame('c', $pipeline('a'));
+        $this->assertSame('d', $second('a'));
+    }
+
+    public function testPipelinePrepend()
+    {
+        $pipeline = f\pipe(
+            [$this->mock, 'b'],
+            [$this->mock, 'c']
+        );
+
+        $second = $pipeline->prepend([$this->mock, 'a']);
+
+        $this->mock->method('a')->willReturn('b');
+        $this->mock->method('b')->willReturn('c');
+        $this->mock->method('c')->willReturn('d');
+
+        $this->mock->expects($this->exactly(1))->method('a')->with('a');
+        $this->mock->expects($this->exactly(2))->method('b')->with('b');
+        $this->mock->expects($this->exactly(2))->method('c')->with('c');
+
+        $this->assertSame('d', $pipeline('b'));
+        $this->assertSame('d', $second('a'));
+    }
+}

tests/bootstrap.php

@@ -8,4 +8,4 @@
  */
 
 require_once __DIR__.'/../vendor/autoload.php';
-require_once __DIR__.'/RandomDataTrait.php';
+require_once __DIR__.'/RandomDataTrait.php';