chore: snapshot before performance optimization

keep-notes/lib/i18n/detect-user-language.ts

@@ -1,62 +1,54 @@
 /**
  * Detect user's preferred language from their existing notes
- * Analyzes language distribution across all user's notes
+ * Uses a single DB-level GROUP BY query — no note content is loaded
  */
 
 import { auth } from '@/auth'
 import { prisma } from '@/lib/prisma'
+import { unstable_cache } from 'next/cache'
 import { SupportedLanguage } from './load-translations'
 
+const SUPPORTED_LANGUAGES = new Set(['en', 'fr', 'es', 'de', 'fa', 'it', 'pt', 'ru', 'zh', 'ja', 'ko', 'ar', 'hi', 'nl', 'pl'])
+
+const getCachedUserLanguage = unstable_cache(
+  async (userId: string): Promise<SupportedLanguage> => {
+    try {
+      // Single aggregated query — no notes are fetched, only language counts
+      const result = await prisma.note.groupBy({
+        by: ['language'],
+        where: {
+          userId,
+          language: { not: null }
+        },
+        _sum: { languageConfidence: true },
+        _count: true,
+        orderBy: { _sum: { languageConfidence: 'desc' } },
+        take: 1,
+      })
+
+      if (result.length > 0 && result[0].language) {
+        const topLanguage = result[0].language as SupportedLanguage
+        if (SUPPORTED_LANGUAGES.has(topLanguage)) {
+          return topLanguage
+        }
+      }
+
+      return 'en'
+    } catch (error) {
+      console.error('Error detecting user language:', error)
+      return 'en'
+    }
+  },
+  ['user-language'],
+  { tags: ['user-language'] }
+)
+
 export async function detectUserLanguage(): Promise<SupportedLanguage> {
   const session = await auth()
 
-  // Default to English for non-logged-in users
   if (!session?.user?.id) {
     return 'en'
   }
 
-  try {
-    // Get all user's notes with detected languages
-    const notes = await prisma.note.findMany({
-      where: {
-        userId: session.user.id,
-        language: { not: null }
-      },
-      select: {
-        language: true,
-        languageConfidence: true
-      }
-    })
-
-    if (notes.length === 0) {
-      return 'en' // Default for new users
-    }
-
-    // Count language occurrences weighted by confidence
-    const languageScores: Record<string, number> = {}
-
-    for (const note of notes) {
-      if (note.language) {
-        const confidence = note.languageConfidence || 0.8
-        languageScores[note.language] = (languageScores[note.language] || 0) + confidence
-      }
-    }
-
-    // Find language with highest score
-    const sortedLanguages = Object.entries(languageScores)
-      .sort(([, a], [, b]) => b - a)
-
-    if (sortedLanguages.length > 0) {
-      const topLanguage = sortedLanguages[0][0] as SupportedLanguage
-      // Verify it's a supported language
-      if (['en', 'fr', 'es', 'de', 'fa', 'it', 'pt', 'ru', 'zh', 'ja', 'ko', 'ar', 'hi', 'nl', 'pl'].includes(topLanguage)) {
-        return topLanguage
-      }
-    }
-
-    return 'en'
-  } catch (error) {
-    console.error('Error detecting user language:', error)
-    return 'en'
-  }
+  return getCachedUserLanguage(session.user.id)
 }