From df0cab306ce8fb2a1b870046441ded6ff1ed95f8 Mon Sep 17 00:00:00 2001
From: Casey McLaughlin <caseyamcl@gmail.com>
Date: Tue, 1 Oct 2019 15:54:44 -0400
Subject: [PATCH] Trim empty levels from top of menu tree (fixes #1)

---
 CHANGELOG.md               |  1 +
 src/TocGenerator.php       | 33 +++++++++++++++++++++++---
 tests/TocGeneratorTest.php | 47 ++++++++++++++++++++++++++++++++++++--
 3 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1ae0135..4ec04a9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ All notable changes to this project are documented in this file.
 ### Fixed
 - Several issues in the README (typos, etc)
 - Version number in COPYRIGHT notice
+- Empty levels are now automatically trimmed from the generated output (fixes #1) 
 
 ### Changed
 - Updated PHP requirements to modern versions (7.1+)
diff --git a/src/TocGenerator.php b/src/TocGenerator.php
index bbab80d..c3707f7 100644
--- a/src/TocGenerator.php
+++ b/src/TocGenerator.php
@@ -36,6 +36,8 @@ class TocGenerator
 {
     use HtmlHelper;
 
+    private const DEFAULT_NAME = 'TOC';
+
     /**
      * @var HTML5
      */
@@ -71,7 +73,7 @@ public function __construct(MenuFactory $menuFactory = null, HTML5 $htmlParser =
     public function getMenu(string $markup, int $topLevel = 1, int $depth = 6): ItemInterface
     {
         // Setup an empty menu object
-        $menu = $this->menuFactory->createItem('TOC');
+        $menu = $this->menuFactory->createItem(static::DEFAULT_NAME);
 
         // Empty?  Return empty menu item
         if (trim($markup) == '') {
@@ -86,7 +88,7 @@ public function getMenu(string $markup, int $topLevel = 1, int $depth = 6): Item
 
         // Do it...
         $domDocument = $this->domParser->loadHTML($markup);
-        foreach ($this->traverseHeaderTags($domDocument, $topLevel, $depth) as $node) {
+        foreach ($this->traverseHeaderTags($domDocument, $topLevel, $depth) as $i => $node) {
             // Skip items without IDs
             if (! $node->hasAttribute('id')) {
                 continue;
@@ -123,7 +125,32 @@ public function getMenu(string $markup, int $topLevel = 1, int $depth = 6): Item
             );
         }
 
-        return $menu;
+        return $this->trimMenu($menu);
+    }
+
+    /**
+     * Trim empty items from the menu
+     *
+     * @param ItemInterface $menuItem
+     * @return ItemInterface
+     */
+    protected function trimMenu(ItemInterface $menuItem): ItemInterface
+    {
+        // if any of these circumstances are true, then just bail and return the menu item
+        if (
+            count($menuItem->getChildren()) === 0
+            or count($menuItem->getChildren()) > 1
+            or ! empty($menuItem->getFirstChild()->getLabel())
+        ) {
+            return $menuItem;
+        }
+
+        // otherwise, find the first level where there is actual content and use that.
+        while (count($menuItem->getChildren()) == 1 && empty($menuItem->getFirstChild()->getLabel())) {
+            $menuItem = $menuItem->getFirstChild();
+        }
+
+        return $menuItem;
     }
 
     /**
diff --git a/tests/TocGeneratorTest.php b/tests/TocGeneratorTest.php
index cacb4f9..4a17b81 100644
--- a/tests/TocGeneratorTest.php
+++ b/tests/TocGeneratorTest.php
@@ -19,6 +19,7 @@
 
 namespace TOC;
 
+use Knp\Menu\ItemInterface;
 use PHPUnit\Framework\TestCase;
 use TOC\Util\TOCTestUtils;
 
@@ -64,7 +65,7 @@ public function testGetMenuTraversesLevelsCorrectly(): void
         $this->assertEquals($fixture, $actual);
     }
 
-    public function testGetMenuGeneratesIdsForElementsWithoutIDs(): void
+    public function testGetMenuDoesNotGenerateIDsForElementsWithoutIDs(): void
     {
         $html = "
             <h1 id='a'>A-Header</h1><p>Foobar</p>
@@ -121,11 +122,53 @@ public function testGetMenuReturnsEmptyMenuItemWhenNoContentOrMatches(): void
         $this->assertEquals(0, count($obj->getMenu("")));
     }
 
-    public function testGetMenuRespectsOlOption(): void
+    public function testGetOrderedMenu(): void
     {
         $obj = new TocGenerator();
         $html = "<h1 id='x'>A-Header</h1><h1 id='y'>A-Header</h1>";
         $menuHtml = $obj->getOrderedHtmlMenu($html, 1, 6, null);
         $this->assertStringStartsWith('<ol>', $menuHtml);
     }
+
+    /**
+     * @dataProvider unusedHeadingLevelsAreTrimmedDataProvider
+     * @param ItemInterface $menuItem
+     * @param int $expectedTopLevelItems
+     * @param int $expectedSubItems
+     */
+    public function testUnusedHeadingLevelsAreTrimmedFromGeneratedMenu(
+        ItemInterface $menuItem,
+        int $expectedTopLevelItems,
+        int $expectedSubItems = 0
+    ): void {
+        $this->assertEquals($expectedTopLevelItems, count($menuItem->getChildren()));
+
+        if ($expectedSubItems > 0) {
+            $this->assertEquals($expectedSubItems, count($menuItem->getFirstChild()->getChildren()));
+        }
+    }
+
+    /**
+     * @return iterable|ItemInterface[]
+     */
+    public function unusedHeadingLevelsAreTrimmedDataProvider(): iterable
+    {
+        $obj = new TocGenerator();
+
+        yield [
+            $obj->getMenu("<h3 id='x'>X-Header</h3><h4 id='y'>Y-Header</h4><h4 id='z'>Z-Header</h4>", 1, 6),
+            1,
+            2
+        ];
+
+        yield [$obj->getMenu("<h1 id='x'>X-Header</h1>", 1, 6), 1];
+
+        yield [
+            $obj->getMenu('<h5 id="x">X-Header</h5><h5 id="y">Y-Header</h5>', 1, 6), 2
+        ];
+
+        yield [
+            $obj->getMenu('<h6 id="y">Y-Header</h6>', 1, 5), 0
+        ];
+    }
 }