New Intersect and IntersectKeys operation.

spec/loophp/collection/CollectionSpec.php

@@ -998,6 +998,30 @@ public function it_can_implode(): void
             ->shouldReturn('ABC');
     }
 
+    public function it_can_intersect(): void
+    {
+        $this::fromIterable(range(1, 5))
+            ->intersect(1, 2, 3, 9)
+            ->shouldIterateAs([0 => 1, 1 => 2, 2 => 3]);
+
+        $this::fromIterable(range(1, 5))
+            ->intersect()
+            ->shouldIterateAs([]);
+    }
+
+    public function it_can_intersectKeys(): void
+    {
+        $input = array_combine(range('a', 'e'), range(1, 5));
+
+        $this::fromIterable($input)
+            ->intersectKeys('b', 'd')
+            ->shouldIterateAs(['b' => 2, 'd' => 4]);
+
+        $this::fromIterable($input)
+            ->intersectKeys()
+            ->shouldIterateAs([]);
+    }
+
     public function it_can_intersperse(): void
     {
         $this::fromIterable(range('A', 'F'))

src/Collection.php

@@ -31,6 +31,8 @@
 use loophp\collection\Operation\Forget;
 use loophp\collection\Operation\Frequency;
 use loophp\collection\Operation\Group;
+use loophp\collection\Operation\Intersect;
+use loophp\collection\Operation\IntersectKeys;
 use loophp\collection\Operation\Intersperse;
 use loophp\collection\Operation\Iterate;
 use loophp\collection\Operation\Keys;
@@ -272,6 +274,16 @@ public function implode(string $glue = ''): string
         return $this->transform(new Implode($glue));
     }
 
+    public function intersect(...$values): BaseInterface
+    {
+        return $this->run(new Intersect(...$values));
+    }
+
+    public function intersectKeys(...$values): BaseInterface
+    {
+        return $this->run(new IntersectKeys(...$values));
+    }
+
     public function intersperse($element, int $every = 1, int $startAt = 0): BaseInterface
     {
         return $this->run(new Intersperse($element, $every, $startAt));

src/Contract/Collection.php

@@ -25,6 +25,8 @@
 use loophp\collection\Contract\Operation\Forgetable;
 use loophp\collection\Contract\Operation\Frequencyable;
 use loophp\collection\Contract\Operation\Groupable;
+use loophp\collection\Contract\Operation\Intersectable;
+use loophp\collection\Contract\Operation\Intersectkeysable;
 use loophp\collection\Contract\Operation\Intersperseable;
 use loophp\collection\Contract\Operation\Iterateable;
 use loophp\collection\Contract\Operation\Keysable;
@@ -104,6 +106,8 @@ interface Collection extends
     Getable,
     Groupable,
     Implodeable,
+    Intersectable,
+    Intersectkeysable,
     Intersperseable,
     Iterateable,
     JsonSerializable,

src/Contract/Operation/Intersectable.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Contract\Operation;
+
+use loophp\collection\Contract\Base;
+
+interface Intersectable
+{
+    /**
+     * @param mixed ...$values
+     *
+     * @return \loophp\collection\Base|\loophp\collection\Contract\Collection
+     */
+    public function intersect(...$values): Base;
+}

src/Contract/Operation/Intersectkeysable.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Contract\Operation;
+
+use loophp\collection\Contract\Base;
+
+interface Intersectkeysable
+{
+    /**
+     * @param mixed ...$values
+     *
+     * @return \loophp\collection\Base|\loophp\collection\Contract\Collection
+     */
+    public function intersectKeys(...$values): Base;
+}

src/Operation/Intersect.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Operation;
+
+use Closure;
+use Generator;
+use loophp\collection\Contract\Operation;
+
+use function in_array;
+
+final class Intersect extends AbstractOperation implements Operation
+{
+    /**
+     * @param mixed ...$values
+     */
+    public function __construct(...$values)
+    {
+        $this->storage['values'] = $values;
+    }
+
+    public function __invoke(): Closure
+    {
+        return
+            /**
+             * @param array<int, mixed> $values
+             */
+            static function (iterable $collection, $values): Generator {
+                foreach ($collection as $key => $value) {
+                    if (true === in_array($value, $values, true)) {
+                        yield $key => $value;
+                    }
+                }
+            };
+    }
+}

src/Operation/IntersectKeys.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Operation;
+
+use Closure;
+use Generator;
+use loophp\collection\Contract\Operation;
+
+use function in_array;
+
+final class IntersectKeys extends AbstractOperation implements Operation
+{
+    /**
+     * @param mixed ...$values
+     */
+    public function __construct(...$values)
+    {
+        $this->storage['values'] = $values;
+    }
+
+    public function __invoke(): Closure
+    {
+        return
+            /**
+             * @param array<int, mixed> $values
+             */
+            static function (iterable $collection, $values): Generator {
+                foreach ($collection as $key => $value) {
+                    if (true === in_array($key, $values, true)) {
+                        yield $key => $value;
+                    }
+                }
+            };
+    }
+}