feat(flashcards): révision SM-2, génération IA et page /revision

Livre US-FLASHCARDS avec decks, session de révision, stats et migration Prisma. Finalise le Web Clipper (i18n 15 langues) et corrige les erreurs ESLint bloquant la CI.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/app/api/flashcards/stats/route.ts

@@ -0,0 +1,80 @@
+import { NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import prisma from '@/lib/prisma'
+import { isCardMastered } from '@/lib/flashcards/sm2'
+
+export async function GET() {
+  try {
+    const session = await auth()
+    if (!session?.user?.id) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+    }
+
+    const userId = session.user.id
+    const now = new Date()
+
+    const [reviews, allCards] = await Promise.all([
+      prisma.flashcardReview.findMany({
+        where: { card: { deck: { userId } } },
+        select: { reviewedAt: true, grade: true },
+        orderBy: { reviewedAt: 'desc' },
+        take: 500,
+      }),
+      prisma.flashcard.findMany({
+        where: { deck: { userId } },
+        select: { id: true, interval: true, easinessFactor: true, front: true, deck: { select: { name: true } } },
+      }),
+    ])
+
+    const heatmapMap = new Map<string, number>()
+    for (const r of reviews) {
+      const day = r.reviewedAt.toISOString().slice(0, 10)
+      heatmapMap.set(day, (heatmapMap.get(day) || 0) + 1)
+    }
+    const heatmap = Array.from(heatmapMap.entries())
+      .map(([date, count]) => ({ date, count }))
+      .sort((a, b) => a.date.localeCompare(b.date))
+      .slice(-90)
+
+    const totalCards = allCards.length
+    const masteredCount = allCards.filter((c) => isCardMastered(c.interval)).length
+    const retentionRate = totalCards > 0 ? Math.round((masteredCount / totalCards) * 100) : 0
+
+    const weekMs = 7 * 24 * 60 * 60 * 1000
+    const retentionByWeek: { week: string; rate: number }[] = []
+    for (let i = 7; i >= 0; i--) {
+      const weekEnd = new Date(now.getTime() - i * weekMs)
+      const weekStart = new Date(weekEnd.getTime() - weekMs)
+      const cardsAtWeek = allCards.filter((c) => c.interval >= 7 * (8 - i))
+      const masteredAtWeek = cardsAtWeek.filter((c) => isCardMastered(c.interval)).length
+      const rate = cardsAtWeek.length > 0
+        ? Math.round((masteredAtWeek / cardsAtWeek.length) * 100)
+        : retentionRate
+      retentionByWeek.push({
+        week: weekStart.toISOString().slice(0, 10),
+        rate,
+      })
+    }
+
+    const difficultCards = [...allCards]
+      .sort((a, b) => a.easinessFactor - b.easinessFactor)
+      .slice(0, 5)
+      .map((c) => ({
+        id: c.id,
+        front: c.front.slice(0, 120),
+        easinessFactor: c.easinessFactor,
+        deckName: c.deck.name,
+      }))
+
+    return NextResponse.json({
+      heatmap,
+      retentionRate,
+      retentionByWeek,
+      difficultCards,
+      totalReviews: reviews.length,
+    })
+  } catch (error) {
+    console.error('[flashcards/stats]', error)
+    return NextResponse.json({ error: 'Failed to load stats' }, { status: 500 })
+  }
+}