⚙️ Engine: O(1) Column Indexing & Allocation-Free Date Formatting

.Jules/engine.md

@@ -29,3 +29,8 @@
 - **Edge Memory & Performance:** Refactored `splitReleaseBody` in `src/utils/github-releases.ts` and `toVisitorReleaseBody` in `src/utils/visitor-changelog.ts` to use pointer-based line scanning (`indexOf('\n', startPos)`), eliminating dynamic `body.split('\n')` string array allocations during SSR and API execution.
 - **Sentence Counting Optimization:** Refactored `sentenceCount` in `src/utils/release-summary.ts` from regex lookbehind `.split(/(?<=[.!?])\s+/)` into a single-pass character scanning loop. Added whitespace-aware sentence boundary detection to safely ignore dots inside version strings (`2026.08.15.1714`).
 - **Verification:** Added Vitest unit test cases across `release-summary.test.ts`, `visitor-changelog.test.ts`, and `github-releases.test.ts` covering version numbers, CRLF line endings, multiple trailing punctuation, and whitespace handling.
+
+## 2025-06-18 - O(1) Column Map Indexing & Allocation-Free Date Formatting
+
+- **O(1) Column Indexing:** Refactored `parseVisitGlance` in `src/utils/visit-stats.ts` to pre-construct a `Map<string, number>` once per payload from column name arrays. Replaced repeated $O(N)$ `columns.indexOf(key)` array searches across 12 row fields with $O(1)$ map index lookups.
+- **Allocation-Free Date Formatting:** Refactored `formatReleaseDate` in `src/utils/github-releases.ts` to use `date.toISOString().slice(0, 10)` instead of `.split('T')[0]`, eliminating dynamic intermediate string array allocations on Cloudflare Workers V8 edge runtimes.

src/utils/github-releases.ts

@@ -176,7 +176,7 @@ export function formatReleaseDate(dateString: string | null): string {
     return 'Unknown date';
   }
 
-  return date.toISOString().split('T')[0];
+  return date.toISOString().slice(0, 10);
 }
 
 /**

src/utils/visit-stats.ts

@@ -47,16 +47,16 @@ function asIsoTimestamp(raw: unknown): string | null {
 
 function valueFromRow(
   row: unknown,
-  columns: string[] | undefined,
+  columnMap: Map<string, number> | undefined,
   key: string,
   index: number
 ): unknown {
   if (row && typeof row === 'object' && !Array.isArray(row) && key in row) {
     return (row as Record<string, unknown>)[key];
   }
-  if (Array.isArray(row) && columns) {
-    const colIndex = columns.indexOf(key);
-    if (colIndex >= 0) return row[colIndex];
+  if (Array.isArray(row) && columnMap) {
+    const colIndex = columnMap.get(key);
+    if (colIndex !== undefined) return row[colIndex];
   }
   if (Array.isArray(row)) return row[index];
   return undefined;
@@ -76,26 +76,31 @@ export function parseVisitGlance(payload: unknown): VisitGlance | null {
   if (!Array.isArray(results) || results.length === 0) return null;
 
   const columns = (payload as { columns?: unknown }).columns;
-  const columnNames = Array.isArray(columns)
-    ? columns.filter((c): c is string => typeof c === 'string')
-    : undefined;
+  let columnMap: Map<string, number> | undefined;
+  if (Array.isArray(columns)) {
+    columnMap = new Map();
+    for (let i = 0; i < columns.length; i++) {
+      const c = columns[i];
+      if (typeof c === 'string') {
+        columnMap.set(c, i);
+      }
+    }
+  }
 
   const row = results[0];
-  const pageviews = asFiniteNumber(valueFromRow(row, columnNames, 'pageviews', 0));
-  const uniqueVisitors = asFiniteNumber(valueFromRow(row, columnNames, 'unique_visitors', 1));
-  const firstSeen = asIsoTimestamp(valueFromRow(row, columnNames, 'first_seen', 2));
-  const pageviews7d = asFiniteNumber(valueFromRow(row, columnNames, 'pageviews_7d', 3));
-  const uniqueVisitors7d = asFiniteNumber(valueFromRow(row, columnNames, 'unique_visitors_7d', 4));
-  const unique1d = asFiniteNumber(valueFromRow(row, columnNames, 'unique_visitors_1d', 5));
-  const unique1dPrev = asFiniteNumber(valueFromRow(row, columnNames, 'unique_visitors_1d_prev', 6));
-  const unique7dPrev = asFiniteNumber(valueFromRow(row, columnNames, 'unique_visitors_7d_prev', 7));
-  const unique30d = asFiniteNumber(valueFromRow(row, columnNames, 'unique_visitors_30d', 8));
-  const unique30dPrev = asFiniteNumber(
-    valueFromRow(row, columnNames, 'unique_visitors_30d_prev', 9)
-  );
-  const unique365d = asFiniteNumber(valueFromRow(row, columnNames, 'unique_visitors_365d', 10));
+  const pageviews = asFiniteNumber(valueFromRow(row, columnMap, 'pageviews', 0));
+  const uniqueVisitors = asFiniteNumber(valueFromRow(row, columnMap, 'unique_visitors', 1));
+  const firstSeen = asIsoTimestamp(valueFromRow(row, columnMap, 'first_seen', 2));
+  const pageviews7d = asFiniteNumber(valueFromRow(row, columnMap, 'pageviews_7d', 3));
+  const uniqueVisitors7d = asFiniteNumber(valueFromRow(row, columnMap, 'unique_visitors_7d', 4));
+  const unique1d = asFiniteNumber(valueFromRow(row, columnMap, 'unique_visitors_1d', 5));
+  const unique1dPrev = asFiniteNumber(valueFromRow(row, columnMap, 'unique_visitors_1d_prev', 6));
+  const unique7dPrev = asFiniteNumber(valueFromRow(row, columnMap, 'unique_visitors_7d_prev', 7));
+  const unique30d = asFiniteNumber(valueFromRow(row, columnMap, 'unique_visitors_30d', 8));
+  const unique30dPrev = asFiniteNumber(valueFromRow(row, columnMap, 'unique_visitors_30d_prev', 9));
+  const unique365d = asFiniteNumber(valueFromRow(row, columnMap, 'unique_visitors_365d', 10));
   const unique365dPrev = asFiniteNumber(
-    valueFromRow(row, columnNames, 'unique_visitors_365d_prev', 11)
+    valueFromRow(row, columnMap, 'unique_visitors_365d_prev', 11)
   );
 
   if (