import { NextRequest, NextResponse } from 'next/server'
import prisma from '@/lib/prisma'
import { getMobileUserId } from '@/lib/mobile-auth'
import { generateFlashcardsFromNote, type FlashcardStyle } from '@/lib/flashcards/generate-flashcards'
import { stripHtmlToText } from '@/lib/flashcards/deck-utils'
import { checkEntitlementOrThrow, QuotaExceededError, incrementUsageAsync } from '@/lib/entitlements'

export async function POST(req: NextRequest) {
  const userId = getMobileUserId(req)
  if (!userId) return NextResponse.json({ error: 'Non autorisé' }, { status: 401 })

  const body = await req.json().catch(() => ({}))
  const noteId = typeof body.noteId === 'string' ? body.noteId : null
  const count = typeof body.count === 'number' ? Math.min(body.count, 20) : 10
  const styleRaw = typeof body.style === 'string' ? body.style : 'qa'
  const style: FlashcardStyle = ['qa', 'cloze', 'concept'].includes(styleRaw) ? (styleRaw as FlashcardStyle) : 'qa'

  if (!noteId) return NextResponse.json({ error: 'noteId requis' }, { status: 400 })

  const note = await prisma.note.findFirst({
    where: { id: noteId, userId, trashedAt: null },
    select: { id: true, title: true, content: true, notebookId: true, language: true },
  })
  if (!note) return NextResponse.json({ error: 'Note introuvable' }, { status: 404 })

  const textContent = stripHtmlToText(note.content)
  if (textContent.length < 80) {
    return NextResponse.json({ error: 'Contenu insuffisant pour générer des flashcards (minimum 80 caractères)' }, { status: 400 })
  }

  try {
    await checkEntitlementOrThrow(userId, 'ai_flashcard')
  } catch (err) {
    if (err instanceof QuotaExceededError) {
      return NextResponse.json({ error: err.currentQuota === 0 ? 'Fonctionnalité non disponible sur votre abonnement' : 'Quota IA atteint' }, { status: 402 })
    }
    throw err
  }

  const cards = await generateFlashcardsFromNote({
    title: note.title || 'Sans titre',
    textContent,
    count,
    style,
    language: note.language || undefined,
  })

  if (cards.length === 0) {
    return NextResponse.json({ error: 'Génération échouée — aucune carte produite' }, { status: 500 })
  }

  // Chercher un deck existant pour cette note, ou en créer un
  const existing = await prisma.flashcard.findFirst({
    where: { noteId: note.id, deck: { userId } },
    select: { deckId: true },
  })

  let deckId: string
  if (existing) {
    deckId = existing.deckId
    // Supprimer les anciennes cartes pour les remplacer
    await prisma.flashcard.deleteMany({ where: { noteId: note.id, deckId } })
  } else {
    const deck = await prisma.flashcardDeck.create({
      data: { userId, notebookId: note.notebookId, name: note.title || 'Sans titre' },
    })
    deckId = deck.id
  }

  await prisma.flashcard.createMany({
    data: cards.map((c) => ({
      deckId,
      noteId: note.id,
      front: c.front,
      back: c.back,
      type: c.type,
    })),
  })

  await prisma.flashcardDeck.update({ where: { id: deckId }, data: { updatedAt: new Date() } })
  incrementUsageAsync(userId, 'ai_flashcard')

  return NextResponse.json({ deckId, count: cards.length, cards })
}