Chore/434 parent title interface

CHANGELOG.md

@@ -11,7 +11,9 @@ and this project adheres to
 ### Changed
 
 - Use custom classes for navigation data
-- Create interfaces for page navigation
+- Create interfaces for page navigation 
+- [BREAKING] default value for subItems in PageNavigation introduced as part of interface refactor
+- Create interface for parent title
 
 ## [v2.4.1] - 2026-05-28
 

spec/multipage_parent_title.spec.php

@@ -0,0 +1,67 @@
+<?php
+
+describe(\LongReadPlugin\MultipageParentTitle::class, function () {
+	beforeEach(function () {
+		$this->parentTitle = new \LongReadPlugin\MultipageParentTitle();
+	});
+	it('implements the ParentTitleRetrieverInterface', function () {
+		expect($this->parentTitle)->toBeAnInstanceOf(\LongReadPlugin\ParentTitleRetrieverInterface::class);
+	});
+
+	describe('->get()', function () {
+		it('returns null when post has no ancestors', function () {
+			global $post;
+			$post = (object) [
+				'ID' => 123
+			];
+
+			allow('get_post_ancestors')->toBeCalled()->andReturn([]);
+
+			$result = $this->parentTitle->get();
+
+			expect($result)->toBeNull();
+		});
+
+		it('returns the top-level ancestor title', function () {
+			global $post;
+			$post = (object) [
+				'ID' => 789
+			];
+
+			allow('get_post_ancestors')->toBeCalled()->andReturn([456, 123]);
+			allow('get_the_title')->toBeCalled()->andReturn('Top Level Post');
+			expect('get_the_title')->toBeCalled()->with(123);
+
+			$result = $this->parentTitle->get();
+			expect($result)->toEqual('Top Level Post');
+		});
+
+		it('returns null when get_the_title returns false', function () {
+			global $post;
+			$post = (object) [
+				'ID' => 789
+			];
+
+			allow('get_post_ancestors')->toBeCalled()->andReturn([456, 123]);
+			allow('get_the_title')->toBeCalled()->andReturn(false);
+
+			$result = $this->parentTitle->get();
+
+			expect($result)->toBeNull();
+		});
+
+		it('handles single-level hierarchy', function () {
+			global $post;
+			$post = (object) [
+				'ID' => 456
+			];
+
+			allow('get_post_ancestors')->toBeCalled()->andReturn([123]);
+			allow('get_the_title')->toBeCalled()->andReturn('Parent Post');
+
+			$result = $this->parentTitle->get();
+
+			expect($result)->toEqual('Parent Post');
+		});
+	});
+});

spec/parent_title.spec.php

@@ -1,39 +1,29 @@
 <?php
 
 describe(\LongReadPlugin\ParentTitle::class, function () {
-	describe('::get', function () {
-		context('there is no post parent', function () {
-			it('returns null', function () {
-				global $post;
-				$post = new stdClass();
-				allow('get_post_ancestors')->toBeCalled()->andReturn([]);
-				$result = \LongReadPlugin\ParentTitle::get();
-				expect($result)->toEqual(null);
-			});
-		});
+	describe('::get()', function () {
+		it('calls the getter instance method and returns its result', function () {
+			$mockGetter = \Kahlan\Plugin\Double::instance([
+				'implements' => \LongReadPlugin\ParentTitleRetrieverInterface::class
+			]);
+			allow($mockGetter)->toReceive('get')->andReturn('Parent Title');
+
+			new \LongReadPlugin\ParentTitle($mockGetter);
+			$result = \LongReadPlugin\ParentTitle::get();
 
-		context('there is only one post ancestors', function () {
-			it('returns the title of that parent', function () {
-				global $post;
-				$post = new stdClass();
-				allow('get_post_ancestors')->toBeCalled()->andReturn([123]);
-				allow('get_the_title')->toBeCalled()->andReturn('The parent title');
-				expect('get_the_title')->toBeCalled()->once()->with(123);
-				$result = \LongReadPlugin\ParentTitle::get();
-				expect($result)->toEqual('The parent title');
-			});
+			expect($result)->toEqual('Parent Title');
 		});
 
-		context('there is only multiple post ancestors', function () {
-			it('returns the title of the top level post ancestor', function () {
-				global $post;
-				$post = new stdClass();
-				allow('get_post_ancestors')->toBeCalled()->andReturn([123, 456, 789]);
-				allow('get_the_title')->toBeCalled()->andReturn('The top ancestor title');
-				expect('get_the_title')->toBeCalled()->once()->with(789);
-				$result = \LongReadPlugin\ParentTitle::get();
-				expect($result)->toEqual('The top ancestor title');
-			});
+		it('returns null when getter returns null', function () {
+			$mockGetter = \Kahlan\Plugin\Double::instance([
+				'implements' => \LongReadPlugin\ParentTitleRetrieverInterface::class
+			]);
+			allow($mockGetter)->toReceive('get')->andReturn(null);
+
+			new \LongReadPlugin\ParentTitle($mockGetter);
+			$result = \LongReadPlugin\ParentTitle::get();
+
+			expect($result)->toBeNull();
 		});
 	});
 });

src/HierarchicalInPageNavigation.php

@@ -10,10 +10,13 @@ class HierarchicalInPageNavigation implements InPageNavigationInterface
 	private function parseHeading(string $html): InPageNavigationItem
 	{
 		$matches = [];
-		preg_match('/(id=")(.*?)"/', $html, $matches);
+		$id = null;
+		if (preg_match('/(id=")(.*?)"/', $html, $matches)) {
+			$id = $matches[2] ?? null;
+		}
 		return new InPageNavigationItem(
 			trim(strip_tags($html)),
-			$matches[2]
+			$id
 		);
 	}
 

src/MultipageParentTitle.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace LongReadPlugin;
+
+class MultipageParentTitle implements ParentTitleRetrieverInterface
+{
+	public function get(): ?string
+	{
+		global $post;
+		$ancestors = get_post_ancestors($post);
+		$topLevelAncestor = array_pop($ancestors);
+		return $topLevelAncestor ? get_the_title($topLevelAncestor) ?: null : null;
+	}
+}

src/ParentTitle.php

@@ -4,16 +4,18 @@
 
 class ParentTitle
 {
-	/**
-	* @return string|null
-	*/
-	public static function get()
+	private static ParentTitleRetrieverInterface $getter;
+
+	public function __construct(ParentTitleRetrieverInterface $getter)
+	{
+		self::$getter = $getter;
+	}
+
+	public static function get(): ?string
 	{
-		global $post;
-		$ancestors = get_post_ancestors($post);
-		$topLevelAncestor = array_pop($ancestors);
-		if ($topLevelAncestor) {
-			return get_the_title($topLevelAncestor);
+		if (!isset(self::$getter)) {
+			return null;
 		}
+		return self::$getter->get();
 	}
 }

src/ParentTitleRetrieverInterface.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace LongReadPlugin;
+
+interface ParentTitleRetrieverInterface
+{
+	public function get(): ?string;
+}

src/di.php

@@ -3,8 +3,11 @@
 $registrar->addInstance(new \LongReadPlugin\PostType());
 $registrar->addInstance(new \LongReadPlugin\HeadingAnchors());
 $registrar->addInstance(new \LongReadPlugin\Navigation(
-	new LongReadPlugin\HierarchicalChapterNavigation(),
-	new LongReadPlugin\HierarchicalInPageNavigation()
+	new \LongReadPlugin\HierarchicalChapterNavigation(),
+	new \LongReadPlugin\HierarchicalInPageNavigation()
 ));
 $registrar->addInstance(new \LongReadPlugin\Options());
 $registrar->addInstance(new \LongReadPlugin\Template());
+$registrar->addInstance(new \LongReadPlugin\ParentTitle(
+	new \LongReadPlugin\MultipageParentTitle()
+));