Refactor and support tree node resolution via ToC entry closure

src/lib/components/publications/table_of_contents.svelte.ts

@@ -1,5 +1,5 @@
 import { SvelteMap } from 'svelte/reactivity';
-import type { SveltePublicationTree } from './svelte_publication_tree.svelte.ts';
+import { SveltePublicationTree } from './svelte_publication_tree.svelte.ts';
 import type { NDKEvent } from '../../utils/nostrUtils.ts';
 
 export interface TocEntry {
@@ -9,6 +9,9 @@ export interface TocEntry {
   children: TocEntry[];
   parent?: TocEntry;
   depth: number;
+  expanded: boolean;
+  childrenResolved: boolean;
+  resolveChildren: () => Promise<void>;
 }
 
 /**
@@ -35,10 +38,7 @@ export class TableOfContents {
   constructor(rootAddress: string, publicationTree: SveltePublicationTree, pagePathname: string) {
     this.#publicationTree = publicationTree;
     this.#pagePathname = pagePathname;
-    void this.#initRoot(rootAddress);
-    this.#publicationTree.onNodeResolved((address: string) => {
-      void this.#handleNodeResolved(address);
-    });
+    this.#init(rootAddress);
   }
 
   // #region Public Methods
@@ -84,12 +84,16 @@ export class TableOfContents {
         if (id && title) {
           const href = `${this.#pagePathname}#${id}`;
 
+          // TODO: Check this logic.
           const tocEntry: TocEntry = {
             address: parentEntry.address,
             title,
             href,
             depth,
             children: [],
+            expanded: false,
+            childrenResolved: true,
+            resolveChildren: () => Promise.resolve(),
           };
           parentEntry.children.push(tocEntry);
 
@@ -127,84 +131,96 @@ export class TableOfContents {
 
   // #region Private Methods
 
-  async #initRoot(rootAddress: string) {
+  async #init(rootAddress: string) {
     const rootEvent = await this.#publicationTree.getEvent(rootAddress);
     if (!rootEvent) {
       throw new Error(`[ToC] Root event ${rootAddress} not found.`);
     }
 
-    this.#root = {
-      address: rootAddress,
-      title: this.#getTitle(rootEvent),
-      children: [],
-      depth: 0,
-    };
+    this.#root = await this.#buildTocEntry(rootAddress);
 
     this.addressMap.set(rootAddress, this.#root);
+
+    // TODO: Parallelize this.
     // Handle any other nodes that have already been resolved.
-    await this.#handleNodeResolved(rootAddress);
-  }
+    this.#publicationTree.resolvedAddresses.forEach(async (address) => {
+      await this.#buildTocEntryFromResolvedNode(address);
+    });
 
-  async #handleNodeResolved(address: string) {
-    if (this.addressMap.has(address)) {
-      return;
+    // Set up an observer to handle progressive resolution of the publication tree.
+    this.#publicationTree.onNodeResolved(async (address: string) => {
+      await this.#buildTocEntryFromResolvedNode(address);
+    });
   }
-    const event = await this.#publicationTree.getEvent(address);
+
+  #getTitle(event: NDKEvent | null): string {
     if (!event) {
-      return;
+      // TODO: What do we want to return in this case?
+      return '[untitled]';
+    }
+    const titleTag = event.getMatchingTags?.('title')?.[0]?.[1];
+    return titleTag || event.tagAddress() || '[untitled]';
   }
 
-    const parentEvent = await this.#publicationTree.getParent(address);
-    const parentAddress = parentEvent?.tagAddress();
-    if (!parentAddress) {
-      // All non-root nodes must have a parent.
-      if (!this.#root || address !== this.#root.address) {
-        throw new Error(`[ToC] Parent not found for address ${address}`);
+  #normalizeHashPath(title: string): string {
+    // TODO: Confirm this uses good normalization logic to produce unique hrefs within the page.
+    return title.toLowerCase().replace(/ /g, '-');
   }
+
+  async #buildTocEntry(address: string): Promise<TocEntry> {
+    const resolver = async () => {
+      if (entry.childrenResolved) {
         return;
       }
 
-    const parentEntry = this.addressMap.get(parentAddress);
-    if (!parentEntry) {
-      throw new Error(`[ToC] Parent ToC entry not found for address ${address}`);
+      const childAddresses = await this.#publicationTree.getChildAddresses(address);
+      for (const childAddress of childAddresses) {
+        if (!childAddress) {
+          continue;
+        }
+
+        // Michael J - 05 June 2025 - The `getChildAddresses` method forces node resolution on the
+        // publication tree.  This is acceptable here, because the tree is always resolved
+        // top-down.  Therefore, by the time we handle a node's resolution, its parent and
+        // siblings have already been resolved.
+        const childEntry = await this.#buildTocEntry(childAddress);
+        childEntry.parent = entry;
+        childEntry.depth = entry.depth + 1;
+        entry.children.push(childEntry);
+        this.addressMap.set(childAddress, childEntry);
+      }
+
+      entry.childrenResolved = true;
     }
 
+    const event = await this.#publicationTree.getEvent(address);
+    if (!event) {
+      throw new Error(`[ToC] Event ${address} not found.`);
+    }
+
+    const depth = (await this.#publicationTree.getHierarchy(address)).length;
+
     const entry: TocEntry = {
       address,
       title: this.#getTitle(event),
+      href: `${this.#pagePathname}#${address}`,
       children: [],
-      parent: parentEntry,
-      depth: parentEntry.depth + 1,
+      depth,
+      expanded: false,
+      childrenResolved: false,
+      resolveChildren: resolver,
     };
   
-    // Michael J - 05 June 2025 - The `getChildAddresses` method forces node resolution on the
-    // publication tree.  This is acceptable here, because the tree is always resolved top-down.
-    // Therefore, by the time we handle a node's resolution, its parent and siblings have already
-    // been resolved.
-    const childAddresses = await this.#publicationTree.getChildAddresses(parentAddress);
-    const filteredChildAddresses = childAddresses.filter((a): a is string => !!a);
-    const insertIndex = filteredChildAddresses.findIndex(a => a === address);
-    if (insertIndex === -1 || insertIndex > parentEntry.children.length) {
-      parentEntry.children.push(entry);
-    } else {
-      parentEntry.children.splice(insertIndex, 0, entry);
-    }
-    
-    this.addressMap.set(address, entry);
+    return entry;
   }
 
-  #getTitle(event: NDKEvent | null): string {
-    if (!event) {
-      // TODO: What do we want to return in this case?
-      return '[untitled]';
-    }
-    const titleTag = event.getMatchingTags?.('title')?.[0]?.[1];
-    return titleTag || event.tagAddress() || '[untitled]';
+  async #buildTocEntryFromResolvedNode(address: string) {
+    if (this.addressMap.has(address)) {
+      return;
     }
 
-  #normalizeHashPath(title: string): string {
-    // TODO: Confirm this uses good normalization logic to produce unique hrefs within the page.
-    return title.toLowerCase().replace(/ /g, '-');
+    const entry = await this.#buildTocEntry(address);
+    this.addressMap.set(address, entry);
   }
 
   // #endregion