Added IfElse strategy. (#6)

Added IfElse strategy.
Changed IfExists strategy to extend IfElse.
Changed Either strategy to extend IfExists.

Author: Bilge

README.md

@@ -31,6 +31,7 @@ Contents
     1. [Either](#either)
     1. [Filter](#filter)
     1. [Flatten](#flatten)
+    1. [IfElse](#ifelse)
     1. [IfExists](#ifexists)
     1. [Join](#join)
     1. [Merge](#merge)
@@ -294,6 +295,7 @@ The following strategies ship with Mapper and provide a suite of commonly used f
  - [Either](#either) – Either uses the primary strategy, if it returns non-null, otherwise delegates to a fallback expression.
  - [Filter](#filter) – Filters null values or values rejected by the specified callback.
  - [Flatten](#flatten) – Moves all nested values to the top level.
+ - [IfElse](#ifelse) – Delegates to one expression or another depending on whether the specified condition strictly evaluates to true.
  - [IfExists](#ifexists) – Delegates to one expression or another depending on whether the specified condition maps to null.
  - [Join](#join) – Joins sub-string expressions together with a glue string.
  - [Merge](#merge) – Merges two data sets together giving precedence to the latter if keys collide.
@@ -577,6 +579,39 @@ $data = [
 
 > [1, 2, 3, 3, 4, 5]
 
+### IfElse
+
+Delegates to one expression or another depending on whether the specified condition strictly evaluates to true.
+
+If the condition does not return a boolean, `InvalidConditionException` is thrown.
+
+#### Signature
+
+```php
+IfElse(callable $condition, Strategy|Mapping|array|mixed $if, Strategy|Mapping|array|mixed $else = null)
+```
+
+ 1. `$condition` – Condition.
+ 2. `$if` – Expression used when condition evaluates to true.
+ 3. `$else` – Expression used when condition evaluates to false.
+
+#### Example
+
+```php
+(new Mapper)->map(
+    ['foo' => 'foo'],
+    new IfElse(
+        function ($data) {
+            return $data['foo'] !== 'bar';
+        },
+        true,
+        false
+    )
+);
+```
+
+> true
+
 ### IfExists
 
 Delegates to one expression or another depending on whether the specified condition maps to null.

src/InvalidConditionException.php

@@ -0,0 +1,10 @@
+<?php
+namespace ScriptFUSION\Mapper;
+
+/**
+ * The exception that is thrown when an invalid condition is specified.
+ */
+class InvalidConditionException extends \RuntimeException
+{
+    // Intentionally empty.
+}

src/Strategy/Either.php

@@ -6,27 +6,14 @@
 /**
  * Either uses the primary strategy, if it returns non-null, otherwise delegates to a fallback expression.
  */
-class Either extends Decorator
+class Either extends IfExists
 {
-    private $expression;
-
     /**
      * @param Strategy $strategy
      * @param Strategy|Mapping|array|mixed $expression
      */
     public function __construct(Strategy $strategy, $expression)
     {
-        parent::__construct($strategy);
-
-        $this->expression = $expression;
-    }
-
-    public function __invoke($data, $context = null)
-    {
-        if (($result = parent::__invoke($data, $context)) !== null) {
-            return $result;
-        }
-
-        return $this->delegate($this->expression, $data, $context);
+        parent::__construct($strategy, $strategy, $expression);
     }
 }

src/Strategy/IfElse.php

@@ -0,0 +1,60 @@
+<?php
+namespace ScriptFUSION\Mapper\Strategy;
+
+use ScriptFUSION\Mapper\InvalidConditionException;
+use ScriptFUSION\Mapper\Mapping;
+
+/**
+ * Delegates to one expression or another depending on whether the specified condition strictly evaluates to true.
+ */
+class IfElse extends Delegate
+{
+    /** @var callable */
+    private $condition;
+
+    /** @var Strategy|Mapping|array|mixed */
+    private $else;
+
+    /**
+     * Initializes this instance with the specified condition, the specified
+     * expression to be resolved when condition is true and, optionally, the
+     * specified expression to be resolved when condition is false.
+     *
+     * @param callable $condition Condition.
+     * @param Strategy|Mapping|array|mixed $if Primary expression.
+     * @param Strategy|Mapping|array|mixed|null $else Optional. Fallback expression.
+     */
+    public function __construct(callable $condition, $if, $else = null)
+    {
+        parent::__construct($if);
+
+        $this->condition = $condition;
+        $this->else = $else;
+    }
+
+    /**
+     * Resolves the stored expression when the stored condition strictly
+     * evaluates to true, otherwise resolve the stored fallback expression.
+     *
+     * @param mixed $data
+     * @param mixed $context
+     *
+     * @throws InvalidConditionException
+     *
+     * @return mixed
+     */
+    public function __invoke($data, $context = null)
+    {
+        $result = call_user_func($this->condition, $data, $context);
+
+        if (!is_bool($result)) {
+            throw new InvalidConditionException('Invalid return from condition: must be of type boolean.');
+        }
+
+        if ($result === true) {
+            return parent::__invoke($data, $context);
+        }
+
+        return $this->delegate($this->else, $data, $context);
+    }
+}

src/Strategy/IfExists.php

@@ -6,14 +6,8 @@
 /**
  * Delegates to one expression or another depending on whether the specified condition maps to null.
  */
-class IfExists extends Decorator
+class IfExists extends IfElse
 {
-    /** @var Strategy|Mapping|array|mixed */
-    private $if;
-
-    /** @var Strategy|Mapping|array|mixed */
-    private $else;
-
     /**
      * Initializes this instance with the specified condition, the specified
      * strategy or mapping to be resolved when condition is non-null and,
@@ -26,30 +20,12 @@ class IfExists extends Decorator
      */
     public function __construct(Strategy $condition, $if, $else = null)
     {
-        parent::__construct($condition);
-
-        $this->if = $if;
-        $this->else = $else;
-    }
-
-    /**
-     * Resolves the stored strategy or mapping when the stored condition
-     * resolves to a non-null value, otherwise returns the stored default
-     * value.
-     *
-     * @param mixed $data
-     * @param mixed $context
-     *
-     * @return mixed
-     */
-    public function __invoke($data, $context = null)
-    {
-        if (parent::__invoke($data, $context) !== null) {
-            return $this->delegate($this->if, $data, $context);
-        }
-
-        if ($this->else !== null) {
-            return $this->delegate($this->else, $data, $context);
-        }
+        parent::__construct(
+            function ($data, $context) use ($condition) {
+                return $this->delegate($condition, $data, $context) !== null;
+            },
+            $if,
+            $else
+        );
     }
 }

test/Functional/DocumentationTest.php

@@ -12,6 +12,7 @@
 use ScriptFUSION\Mapper\Strategy\Either;
 use ScriptFUSION\Mapper\Strategy\Filter;
 use ScriptFUSION\Mapper\Strategy\Flatten;
+use ScriptFUSION\Mapper\Strategy\IfElse;
 use ScriptFUSION\Mapper\Strategy\IfExists;
 use ScriptFUSION\Mapper\Strategy\Join;
 use ScriptFUSION\Mapper\Strategy\Merge;
@@ -221,6 +222,22 @@ public function testFlatten()
         self::assertSame([1, 2, 3, 3, 4, 5], (new Mapper)->map($data, (new Flatten(new Copy('foo')))->ignoreKeys()));
     }
 
+    public function testIfElse()
+    {
+        self::assertTrue(
+            (new Mapper)->map(
+                ['foo' => 'foo'],
+                new IfElse(
+                    function ($data) {
+                        return $data['foo'] !== 'bar';
+                    },
+                    true,
+                    false
+                )
+            )
+        );
+    }
+
     public function testIfExists()
     {
         $data = ['foo' => 'foo'];

test/Integration/Mapper/Strategy/IfElseTest.php

@@ -0,0 +1,51 @@
+<?php
+namespace ScriptFUSIONTest\Integration\Mapper\Strategy;
+
+use ScriptFUSION\Mapper\InvalidConditionException;
+use ScriptFUSION\Mapper\Mapper;
+use ScriptFUSION\Mapper\Strategy\IfElse;
+
+final class IfElseTest extends \PHPUnit_Framework_TestCase
+{
+    private $condition;
+
+    public function setUp()
+    {
+        $this->condition = function ($data) {
+            return array_key_exists('baz', $data) && $data['baz'] === 'qux';
+        };
+    }
+
+    public function testIfElse()
+    {
+        $ifElse = (new IfElse($this->condition, 'foo', 'bar'))->setMapper(new Mapper);
+
+        self::assertSame('foo', $ifElse(['baz' =>  'qux']));
+        self::assertSame('bar', $ifElse(['baz' => 'quux']));
+        self::assertSame('bar', $ifElse([]));
+    }
+
+    public function testOnlyIf()
+    {
+        $ifElse = (new IfElse($this->condition, 'foo'))->setMapper(new Mapper);
+
+        self::assertSame('foo', $ifElse(['baz' =>  'qux']));
+        self::assertNull($ifElse(['baz' => 'quux']));
+        self::assertNull($ifElse([]));
+    }
+
+    public function testStrictness()
+    {
+        $this->setExpectedException(InvalidConditionException::class);
+
+        $ifElse = (new IfElse(
+            function () {
+                return 1;
+            },
+            'foo',
+            'bar'
+        ))->setMapper(new Mapper);
+
+        $ifElse([]);
+    }
+}