Improve title handling again. (Ticket: #PP-1954)

README-CHANGES.xml

@@ -171,7 +171,7 @@
         </c:change>
       </c:changes>
     </c:release>
-    <c:release date="2024-11-26T13:59:24+00:00" is-open="false" ticket-system="org.lyrasis.jira" version="6.6.0">
+    <c:release date="2024-11-26T00:00:00+00:00" is-open="false" ticket-system="org.lyrasis.jira" version="6.6.0">
       <c:changes>
         <c:change date="2024-11-26T00:00:00+00:00" summary="Do not miss non-leaf titles.">
           <c:tickets>
@@ -180,6 +180,15 @@
         </c:change>
       </c:changes>
     </c:release>
+    <c:release date="2024-11-26T18:06:43+00:00" is-open="true" ticket-system="org.lyrasis.jira" version="6.7.0">
+      <c:changes>
+        <c:change date="2024-11-26T00:00:00+00:00" summary="Improve title handling again.">
+          <c:tickets>
+            <c:ticket id="PP-1954"/>
+          </c:tickets>
+        </c:change>
+      </c:changes>
+    </c:release>
   </c:releases>
   <c:ticket-systems>
     <c:ticket-system default="true" id="org.lyrasis.jira" url="https://ebce-lyrasis.atlassian.net/browse/"/>

org.librarysimplified.r2.vanilla/src/main/java/org/librarysimplified/r2/vanilla/internal/SR2NavigationGraphs.kt

@@ -5,19 +5,32 @@ import org.librarysimplified.r2.vanilla.internal.SR2NavigationNode.SR2Navigation
 import org.librarysimplified.r2.vanilla.internal.SR2NavigationNode.SR2NavigationResourceNode
 import org.readium.r2.shared.publication.Link
 import org.readium.r2.shared.publication.Publication
+import org.slf4j.LoggerFactory
+import java.net.URI
 
 object SR2NavigationGraphs {
 
+  private val logger =
+    LoggerFactory.getLogger(SR2NavigationGraphs::class.java)
+
+  private data class FlatTOCLink(
+    val depth: Int,
+    val link: Link,
+  )
+
   fun create(
     publication: Publication,
   ): SR2NavigationGraph {
+    val flatToc = mutableListOf<FlatTOCLink>()
+    flattenTOC(flatToc, publication.tableOfContents, depth = 0)
+
     val readingOrder =
       publication.readingOrder.mapIndexed { index, link ->
-        this.makeReadingOrderNode(publication, index, link)
+        this.makeReadingOrderNode(flatToc, index, link)
       }
     val resources =
       publication.resources.map { link ->
-        this.makeResourceNode(publication, link)
+        this.makeResourceNode(flatToc, link)
       }
 
     return SR2NavigationGraph(
@@ -26,31 +39,48 @@ object SR2NavigationGraphs {
     )
   }
 
+  private fun flattenTOC(
+    flatToc: MutableList<FlatTOCLink>,
+    tableOfContents: List<Link>,
+    depth: Int,
+  ) {
+    for (entry in tableOfContents) {
+      flatToc.add(FlatTOCLink(depth, entry))
+      flattenTOC(
+        flatToc = flatToc,
+        tableOfContents = entry.children,
+        depth = depth + 1,
+      )
+    }
+  }
+
   private fun makeResourceNode(
-    publication: Publication,
+    flatTOC: List<FlatTOCLink>,
     link: Link,
   ): SR2NavigationResourceNode {
     return SR2NavigationResourceNode(
-      navigationPoint = this.makeNavigationPoint(publication, link),
+      navigationPoint = this.makeNavigationPoint(flatTOC, link),
     )
   }
 
   private fun makeReadingOrderNode(
-    publication: Publication,
+    flatTOC: List<FlatTOCLink>,
     index: Int,
     link: Link,
   ): SR2NavigationReadingOrderNode {
     return SR2NavigationReadingOrderNode(
-      navigationPoint = this.makeNavigationPoint(publication, link),
+      navigationPoint = this.makeNavigationPoint(flatTOC, link),
       index = index,
     )
   }
 
-  private fun makeNavigationPoint(publication: Publication, link: Link): SR2NavigationPoint {
-    val title =
-      link.title?.takeIf(String::isNotBlank)
-        ?: titleFromTOC(null, publication.tableOfContents, link)
-        ?: ""
+  private fun makeNavigationPoint(
+    flatTOC: List<FlatTOCLink>,
+    link: Link,
+  ): SR2NavigationPoint {
+    val title = this.findTitleFor(flatTOC, link)
+    this.logger.debug("Title: {} -> {}", link.href, title)
+
     return SR2NavigationPoint(
       title,
       SR2Locator.SR2LocatorPercent.create(link.href, 0.0),
@@ -59,25 +89,69 @@ object SR2NavigationGraphs {
 
   /**
    * Perform a depth-first search for a title in the toc tree.
-   * In case of multiples matches, deeper items have precedence because they're likely to be more specific.
+   * In case of multiples matches, deeper items have precedence because they're likely to be
+   * more specific.
    */
 
-  private fun titleFromTOC(tocEntryParent: Link?, toc: List<Link>, link: Link): String? {
-    for (entry in toc) {
-      this.titleFromTOC(entry, entry.children, link)?.let {
-        return it
-      }
+  private fun findTitleFor(
+    flatTOC: List<FlatTOCLink>,
+    link: Link,
+  ): String {
+    val linkTitle = link.title?.trim()
+    if (!linkTitle.isNullOrBlank()) {
+      return linkTitle
     }
 
-    for (entry in toc) {
-      if (entry.href == link.href && entry.title != null) {
-        return entry.title
-      }
+    val bestLink =
+      flatTOC.filter { flatLink -> hasSuitableTitle(candidateEntry = flatLink.link, link) }
+        .sortedBy(FlatTOCLink::depth)
+        .lastOrNull()
+
+    return bestLink?.link?.title ?: ""
+  }
+
+  private fun hasSuitableTitle(
+    candidateEntry: Link,
+    link: Link,
+  ): Boolean {
+    /*
+     * If there isn't a non-blank title, then we know this entry isn't suitable.
+     */
+
+    val title = candidateEntry.title ?: return false
+    if (title.isBlank()) {
+      return false
+    }
+
+    /*
+     * If the URLs match exactly, then we know this entry is suitable.
+     */
+
+    if (candidateEntry.href == link.href) {
+      return true
     }
 
-    if (tocEntryParent?.href == link.href && tocEntryParent.title != null) {
-      return tocEntryParent.title
+    /*
+     * Otherwise, if we _don't_ have a fragment, and the target link body matches ours but
+     * _does_ have a fragment, we treat it as suitable.
+     */
+
+    try {
+      val linkAsURI = URI.create(link.href.toString())
+      if (!linkAsURI.fragment.isNullOrBlank()) {
+        return false
+      }
+
+      val linkWithoutFragment =
+        URI.create(linkAsURI.toString().substringBefore('#'))
+      val candidateEntryAsURI =
+        URI.create(candidateEntry.href.toString())
+      val candidateEntryWithoutFragment =
+        URI.create(candidateEntryAsURI.toString().substringBefore('#'))
+
+      return candidateEntryWithoutFragment == linkWithoutFragment
+    } catch (e: Exception) {
+      return false
     }
-    return null
   }
 }