From 0acb6b3d47eada67e733a041f650c3adf2719608 Mon Sep 17 00:00:00 2001
From: anyulled <100741+anyulled@users.noreply.github.com>
Date: Mon, 15 Jun 2026 08:38:01 +0000
Subject: [PATCH] feat: optimize tag finding loop in
 app/[year]/tags/[tag]/page.tsx

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
---
 .jules/bolt.md                 |  5 +++++
 app/[year]/tags/[tag]/page.tsx | 31 ++++++++++++++++++++++++++-----
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index 9345ee7a..e2e11609 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -2,3 +2,8 @@
 
 **Learning:** In Next.js/React applications, when grouping items (like schedules or talks) into a `Map` where the values are arrays, using the array spread operator `[...existing, item]` inside a loop (like `forEach` or `map`) causes amortized O(N^2) memory allocations and unnecessary Garbage Collection overhead.
 **Action:** Always use `.push()` on the existing array reference if the data structure permits local mutation. For strict ESLint configurations enforcing `no-restricted-syntax`, extract the existing array, push to it, and handle the fallback elegantly (`if (!existing) { map.set(key, [item]); } else { existing.push(item); }`).
+
+## 2024-05-19 - Avoid flatMap and find for deep tag lookups in large datasets
+
+**Learning:** When searching for a specific item in nested arrays (like finding a specific tag across all talks), using `allTalks.flatMap(getTags).find(...)` creates unnecessary intermediate arrays and forces multiple full O(N) traversals. This is particularly slow during build-time operations like `generateStaticParams` or tag pages rendering with many talks.
+**Action:** Use nested `for...of` loops (or `.some()` with early return and state accumulation) to do a single-pass O(N) search with early breakout to minimize Garbage Collection overhead and CPU cycles.
diff --git a/app/[year]/tags/[tag]/page.tsx b/app/[year]/tags/[tag]/page.tsx
index 35c74f61..5beed8c6 100644
--- a/app/[year]/tags/[tag]/page.tsx
+++ b/app/[year]/tags/[tag]/page.tsx
@@ -47,8 +47,21 @@ export async function generateMetadata({ params }: Readonly<TagPageProps>): Prom
 
   const sessionGroups = await getTalks(year);
   const allTalks = sessionGroups.flatMap((group) => group.sessions);
-  const displayTag =
-    allTalks.flatMap(getTagsFromTalk).find((t) => t.replaceAll(" ", "-").toLowerCase() === decodedTag.toLowerCase()) ?? decodedTag.replaceAll("-", " ");
+  const targetTagLower = decodedTag.toLowerCase();
+  const state = { displayTag: undefined as string | undefined };
+
+  for (const talk of allTalks) {
+    const talkTags = getTagsFromTalk(talk);
+    for (const t of talkTags) {
+      if (t.replaceAll(" ", "-").toLowerCase() === targetTagLower) {
+        state.displayTag = t;
+        break;
+      }
+    }
+    if (state.displayTag) break;
+  }
+
+  const displayTag = state.displayTag ?? decodedTag.replaceAll("-", " ");
 
   return {
     title: `Talks tagged "${displayTag}" - DevBcn ${year}`,
@@ -64,15 +77,23 @@ export default async function TagPage({ params }: Readonly<TagPageProps>) {
   const sessionGroups = await getTalks(year);
   const allTalks = sessionGroups.flatMap((group) => group.sessions);
 
-  const displayTag =
-    allTalks.flatMap(getTagsFromTalk).find((t) => t.replaceAll(" ", "-").toLowerCase() === decodedTag.toLowerCase()) ?? decodedTag.replaceAll("-", " ");
+  const targetTagLower = decodedTag.toLowerCase();
+  const state = { displayTag: undefined as string | undefined };
 
   const filteredTalks = allTalks.filter((talk) => {
     const talkTags = getTagsFromTalk(talk);
 
-    return talkTags.some((t) => t.replaceAll(" ", "-").toLowerCase() === decodedTag.toLowerCase());
+    return talkTags.some((t) => {
+      if (t.replaceAll(" ", "-").toLowerCase() === targetTagLower) {
+        if (!state.displayTag) state.displayTag = t;
+        return true;
+      }
+      return false;
+    });
   });
 
+  const displayTag = state.displayTag ?? decodedTag.replaceAll("-", " ");
+
   if (filteredTalks.length === 0) {
     notFound();
   }