Parse <nav> elements nested in other HTML elements in EPUB 3 navigation documents (#113)

vers-one · web-flow · commit 57a921e88f3a · 2024-06-03T22:11:52.000-04:00
diff --git a/Source/VersOne.Epub.Test/Unit/Readers/Epub3NavDocumentReaderTests.cs b/Source/VersOne.Epub.Test/Unit/Readers/Epub3NavDocumentReaderTests.cs
@@ -159,6 +159,19 @@ public class Epub3NavDocumentReaderTests
             </html>
             """;
 
+        private const string NAV_FILE_WITH_WITH_NON_TOP_LEVEL_NAV_ELEMENT = """
+            <html xmlns="http://www.w3.org/1999/xhtml">
+              <body>
+                <div>
+                  <nav>
+                    <h1>Test header</h1>
+                    <ol />
+                  </nav>
+                </div>
+              </body>
+            </html>
+            """;
+
         private static EpubPackage MinimalEpubPackageWithNav =>
             new
             (
@@ -447,6 +460,12 @@ public async Task ReadEpub3NavDocumentAsyncWithEscapedAHrefTest()
             await TestSuccessfulReadOperation(NAV_FILE_WITH_ESCAPED_HREF_IN_A_ELEMENT, expectedEpub3NavDocument);
         }
 
+        [Fact(DisplayName = "Reading a NAV file with non-top-level 'nav' element should succeed")]
+        public async Task ReadEpub3NavDocumentAsyncWithNonTopLevelNavElementTest()
+        {
+            await TestSuccessfulReadOperation(NAV_FILE_WITH_WITH_NON_TOP_LEVEL_NAV_ELEMENT, MinimalEpub3NavDocumentWithHeader);
+        }
+
         private static async Task TestSuccessfulReadOperation(string navFileContent, Epub3NavDocument expectedEpub3NavDocument, EpubReaderOptions? epubReaderOptions = null)
         {
             TestZipFile testZipFile = CreateTestZipFileWithNavFile(navFileContent);
diff --git a/Source/VersOne.Epub/Readers/Epub3NavDocumentReader.cs b/Source/VersOne.Epub/Readers/Epub3NavDocumentReader.cs
@@ -49,12 +49,24 @@ public Epub3NavDocumentReader(EpubReaderOptions? epubReaderOptions = null)
             XElement htmlNode = navDocument.Element(xhtmlNamespace + "html") ?? throw new Epub3NavException("EPUB parsing error: navigation file does not contain html element.");
             XElement bodyNode = htmlNode.Element(xhtmlNamespace + "body") ?? throw new Epub3NavException("EPUB parsing error: navigation file does not contain body element.");
             List<Epub3Nav> navs = new();
-            foreach (XElement navNode in bodyNode.Elements(xhtmlNamespace + "nav"))
+            ReadEpub3NavsWithinContainerElement(bodyNode, navs);
+            return new(navFileEntryPath, navs);
+        }
+
+        private static void ReadEpub3NavsWithinContainerElement(XElement containerElement, List<Epub3Nav> resultNavs)
+        {
+            foreach (XElement childElement in containerElement.Elements())
             {
-                Epub3Nav epub3Nav = ReadEpub3Nav(navNode);
-                navs.Add(epub3Nav);
+                if (childElement.GetLowerCaseLocalName() == "nav")
+                {
+                    Epub3Nav epub3Nav = ReadEpub3Nav(childElement);
+                    resultNavs.Add(epub3Nav);
+                }
+                else
+                {
+                    ReadEpub3NavsWithinContainerElement(childElement, resultNavs);
+                }
             }
-            return new(navFileEntryPath, navs);
         }
 
         private static Epub3Nav ReadEpub3Nav(XElement navNode)
