From e53c7654128496f5ff0a99810990106b506731a8 Mon Sep 17 00:00:00 2001
From: Oluwatobi Omisakin <omisakin.oluwatobi@gmail.com>
Date: Tue, 30 Apr 2024 01:19:32 +0300
Subject: [PATCH] feat: Fix head to return one element

---
 src/Traits/ArrayPrefix.php     | 27 +++++++++++++++++++++++++--
 tests/ArrayPrefixTraitTest.php | 13 +++++++++----
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/src/Traits/ArrayPrefix.php b/src/Traits/ArrayPrefix.php
index 88b6de0..a1f372d 100644
--- a/src/Traits/ArrayPrefix.php
+++ b/src/Traits/ArrayPrefix.php
@@ -6,6 +6,7 @@
 
 use Transprime\Arrayed\Exceptions\ArrayedException;
 use Transprime\Arrayed\Interfaces\ArrayedInterface;
+use Transprime\Arrayed\Types\Undefined;
 
 /**
  * Trait ArrayPrefix
@@ -80,9 +81,18 @@ public function keysExists(array $needles, bool $all = true): bool
             : (!$intersect->empty());
     }
 
-    public function head(bool $preserveKeys = false): ArrayedInterface
+    /**
+     * @throws ArrayedException
+     * @return ArrayedInterface|mixed
+     */
+    public function head(bool $preserveKeys = false)
     {
-        return $this->slice(0, 1, $preserveKeys);
+        return self::makeArrayed(
+            $this->when($this->getWorkableItem())
+                ->slice(0, 1, $preserveKeys)
+                ->values()
+                ->offsetGet(0)
+        );
     }
 
     public function tail(): ArrayedInterface
@@ -90,6 +100,19 @@ public function tail(): ArrayedInterface
         return $this->slice(1);
     }
 
+    private function when($truthyValue, $default = Undefined::class)
+    {
+        if ($truthyValue) {
+            return $this;
+        }
+
+        if ($default === Undefined::class || $default instanceof Undefined) {
+            throw new \InvalidArgumentException('Value cannot be resolved');
+        }
+
+        return $this->setResult($default);
+    }
+
     /**
      * Forward the calls to `array_*` that is not yet implemented
      * <br>
diff --git a/tests/ArrayPrefixTraitTest.php b/tests/ArrayPrefixTraitTest.php
index 39e2770..91cd397 100644
--- a/tests/ArrayPrefixTraitTest.php
+++ b/tests/ArrayPrefixTraitTest.php
@@ -182,16 +182,21 @@ public function testHead(): void
         $data = ['a', 'b', 'c', 'd'];
 
         $this->assertSame(
-            ['a'],
-            arrayed($data)->head()->result(),
+            'a',
+            arrayed($data)->head(),
         );
 
         $data = ['a' => 'b', 'c' => 'd'];
 
         $this->assertSame(
-            ['a' => 'b'],
-            arrayed($data)->head()->result(),
+            'b',
+            arrayed($data)->head(),
         );
+
+        // Test empty.
+        $this->expectException(\InvalidArgumentException::class);
+
+        arrayed([])->head();
     }
 
     public function testTail(): void