From fb7e2539e6d150036cc9d1ea0c4cb7cfbadcccbc Mon Sep 17 00:00:00 2001
From: buttercat1791 <mjjurkoic@gmail.com>
Date: Sat, 10 May 2025 00:01:52 -0500
Subject: [PATCH] Fix the tree traversal algorithm

The loader's `next()` method now correctly indicates when it has reached the root node in the tree.  From this, the publication component can known when to stop loading and hide the "Load More" button.
---
 src/lib/components/Publication.svelte       |  9 ------
 src/lib/data_structures/publication_tree.ts | 32 +++++++--------------
 2 files changed, 11 insertions(+), 30 deletions(-)

diff --git a/src/lib/components/Publication.svelte b/src/lib/components/Publication.svelte
index adc1489..d8651c5 100644
--- a/src/lib/components/Publication.svelte
+++ b/src/lib/components/Publication.svelte
@@ -43,11 +43,8 @@
     for (let i = 0; i < count; i++) {
       const iterResult = await publicationTree.next();
       const { done, value } = iterResult;
-      
-      console.debug('Iterator result:', iterResult, 'done type:', typeof done);
 
       if (done) {
-        console.debug('Done condition met, setting isDone to true');
         isDone = true;
         break;
       }
@@ -97,10 +94,6 @@
     return () => observer?.unobserve(lastElementRef!);
   });
 
-  $effect(() => {
-    console.debug('isDone changed to:', isDone);
-  });
-
   // #endregion
 
   // #region ToC
@@ -191,7 +184,6 @@
 </script>
 
 <!-- TODO: Keep track of already-loaded leaves. -->
-<!-- TODO: Determine when we've reached the end of the document. -->
 <!-- TODO: Handle entering mid-document and scrolling up. -->
 
 {#if showTocButton && !showToc}
@@ -239,7 +231,6 @@
       />
     {/if}
   {/each}
-  <!-- TODO: Hide the button if there are no more leaves to load. -->
   <div class="flex justify-center my-4">
     {#if isLoading}
       <Button disabled color="primary">
diff --git a/src/lib/data_structures/publication_tree.ts b/src/lib/data_structures/publication_tree.ts
index d703555..f0ecbb6 100644
--- a/src/lib/data_structures/publication_tree.ts
+++ b/src/lib/data_structures/publication_tree.ts
@@ -288,32 +288,22 @@ export class PublicationTree implements AsyncIterable<NDKEvent | null> {
       await this.#cursor.tryMoveTo(this.#bookmark);
     }
 
+    // Based on Raymond Chen's tree traversal algorithm.
+    // https://devblogs.microsoft.com/oldnewthing/20200106-00/?p=103300
     do {
-      if (await this.#cursor.tryMoveToFirstChild()) {
-        continue;
-      }
-
       if (await this.#cursor.tryMoveToNextSibling()) {
-        continue;
-      }
-
-      if (this.#cursor.tryMoveToParent()) {
-        continue;
-      }
-
-      const isRoot = this.#cursor.target?.address === this.#root.address;
-
-      if (isRoot && this.#cursor.target?.type === PublicationTreeNodeType.Branch) {
-        return { done: true, value: null };
-      }
+        while (await this.#cursor.tryMoveToFirstChild()) {
+          continue;
+        }
 
-      if (isRoot && this.#cursor.target?.type === PublicationTreeNodeType.Leaf) {
-        return { done: true, value: this.#events.get(this.#cursor.target!.address)! };
+        const event = await this.getEvent(this.#cursor.target!.address);
+        return { done: false, value: event };
       }
-    } while (this.#cursor.target?.type !== PublicationTreeNodeType.Leaf);
+      this.#cursor.tryMoveToParent();
+    } while (this.#cursor.tryMoveToParent());
 
-    const event = await this.getEvent(this.#cursor.target!.address);
-    return { done: false, value: event };
+    // If we get to this point, we're at the root node (can't move up any more).
+    return { done: true, value: null };
   }
 
   // #endregion