fix(select): default value not being centered when not visible

.gitignore

@@ -1,2 +1,3 @@
+/.idea
 /vendor
 composer.lock

playground/select.php

@@ -5,21 +5,41 @@
 require __DIR__.'/../vendor/autoload.php';
 
 $role = select(
-    label: 'What role should the user have?',
+    label: 'Where are you from?',
     options: [
-        'read-only' => 'Read only',
-        'member' => 'Member',
-        'contributor' => 'Contributor',
-        'supervisor' => 'Supervisor',
-        'manager' => 'Manager',
-        'admin' => 'Administrator',
-        'owner' => 'Owner',
+        'argentina' => 'Argentina',
+        'australia' => 'Australia',
+        'belgium' => 'Belgium',
+        'brazil' => 'Brazil',
+        'canada' => 'Canada',
+        'chile' => 'Chile',
+        'china' => 'China',
+        'colombia' => 'Colombia',
+        'egypt' => 'Egypt',
+        'france' => 'France',
+        'germany' => 'Germany',
+        'india' => 'India',
+        'italy' => 'Italy',
+        'japan' => 'Japan',
+        'kenya' => 'Kenya',
+        'mexico' => 'Mexico',
+        'morocco' => 'Morocco',
+        'nigeria' => 'Nigeria',
+        'new-zealand' => 'New Zealand',
+        'portugal' => 'Portugal',
+        'south-africa' => 'South Africa',
+        'south-korea' => 'South Korea',
+        'spain' => 'Spain',
+        'switzerland' => 'Switzerland',
+        'united-kingdom' => 'United Kingdom',
+        'united-states' => 'United States',
     ],
+    default: 'france',
     validate: fn ($value) => match ($value) {
-        'owner' => 'The owner role is already assigned.',
+        'spain' => 'Spain is not available yet.',
         default => null
     },
-    hint: 'The role will determine what the user can do.',
+    hint: 'The country will determine the currency and the timezone of the user.',
 );
 
 var_dump($role);

src/SelectPrompt.php

@@ -49,6 +49,24 @@ public function __construct(
             } else {
                 $this->highlighted = array_search($this->default, array_keys($this->options)) ?: 0;
             }
+
+            // If the default is not visible, scroll and center it.
+            // If it's near the end of the list, we just scroll to the end.
+            if($this->highlighted >= $this->scroll){
+                $optionsLeft = count($this->options) - $this->highlighted - 1;
+                $halfScroll = (int) floor($this->scroll / 2);
+                $endOffset = max(0, $halfScroll - $optionsLeft);
+
+                // If the scroll is even, we need to subtract one more
+                // in order to take the highlighted option into account.
+                // Since when the scroll is odd the halfScroll is floored,
+                // we don't need to do anything.
+                if($this->scroll % 2 === 0){
+                    $endOffset--;
+                }
+
+                $this->firstVisible = $this->highlighted - $halfScroll - $endOffset;
+            }
         }
 
         $this->on('key', fn ($key) => match ($key) {

tests/Feature/SelectPromptTest.php

@@ -133,3 +133,79 @@
 
     expect($result)->toBe('Blue');
 });
+
+it('centers the default value when it\'s not visible', function () {
+    Prompt::fake([Key::ENTER]);
+
+    $result = select(
+        label: 'What is your favorite color?',
+        options: [
+            'Red',
+            'Green',
+            'Blue',
+            'Yellow',
+            'Orange',
+            'Purple',
+            'Pink',
+            'Brown',
+            'Black',
+        ],
+        default: 'Purple',
+        scroll: 3
+    );
+
+    expect($result)->toBe('Purple');
+
+    Prompt::assertOutputContains('Orange');
+    Prompt::assertOutputContains('Purple');
+    Prompt::assertOutputContains('Pink');
+});
+
+it('scrolls to the bottom when the default value is near the end', function (int $scroll, array $outputContains) {
+    Prompt::fake([Key::ENTER]);
+
+    $result = select(
+        label: 'What is your favorite color?',
+        options: [
+            'Red',
+            'Green',
+            'Blue',
+            'Yellow',
+            'Orange',
+            'Purple',
+            'Pink',
+            'Brown',
+            'Black',
+        ],
+        default: 'Brown',
+        scroll: $scroll
+    );
+
+    expect($result)->toBe('Brown');
+
+    foreach ($outputContains as $output) {
+        Prompt::assertOutputContains($output);
+    }
+})->with([
+    'odd' => [
+        'scroll' => 5,
+        'outputContains' => [
+            'Orange',
+            'Purple',
+            'Pink',
+            'Brown',
+            'Black',
+        ]
+    ],
+    'even' => [
+        'scroll' => 6,
+        'outputContains' => [
+            'Yellow',
+            'Orange',
+            'Purple',
+            'Pink',
+            'Brown',
+            'Black',
+        ]
+    ],
+]);