feat: collection max and min (#264)

src/System/Collection/AbstractCollectionImmutable.php

@@ -338,6 +338,26 @@ public function avg(): int
         return $this->sum() / $this->count();
     }
 
+    /**
+     * Find higest value.
+     *
+     * @param string|int|null $key
+     */
+    public function max($key = null): int
+    {
+        return max(array_column($this->collection, $key));
+    }
+
+    /**
+     * Find lowest value.
+     *
+     * @param string|int|null $key
+     */
+    public function min($key = null): int
+    {
+        return min(array_column($this->collection, $key));
+    }
+
     // array able
 
     /**

tests/Collection/CollectionImmutableTest.php

@@ -219,4 +219,36 @@ public function itCanGetLasts()
 
         $this->assertEquals([80, 90], $coll->lasts(2));
     }
+
+    /** @test */
+    public function itCanGetHigest()
+    {
+        $coll = new CollectionImmutable([10, 20, 30, 40, 50, 60, 70, 80, 90]);
+
+        $this->assertEquals(90, $coll->max());
+
+        $coll = new CollectionImmutable([
+            ['rank' => 10],
+            ['rank' => 50],
+            ['rank' => 90],
+        ]);
+
+        $this->assertEquals(90, $coll->max('rank'));
+    }
+
+    /** @test */
+    public function itCanGetLowestValue()
+    {
+        $coll = new CollectionImmutable([10, 20, 30, 40, 50, 60, 70, 80, 90]);
+
+        $this->assertEquals(10, $coll->min());
+
+        $coll = new CollectionImmutable([
+            ['rank' => 10],
+            ['rank' => 50],
+            ['rank' => 90],
+        ]);
+
+        $this->assertEquals(10, $coll->min('rank'));
+    }
 }