import { NextRequest, NextResponse } from 'next/server'
import { auth } from '@/auth'
import prisma from '@/lib/prisma'
import { getAISettings } from '@/app/actions/ai-settings'
import { reserveUsageOrThrow, QuotaExceededError } from '@/lib/entitlements'
import { hasUserAiConsent } from '@/lib/consent/server-consent'
import { generateFlashcardsFromNote, type FlashcardStyle } from '@/lib/flashcards/generate-flashcards'
import { stripHtmlToText } from '@/lib/flashcards/deck-utils'

export async function POST(request: NextRequest) {
  try {
    const session = await auth()
    if (!session?.user?.id) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
    }

    if (!(await hasUserAiConsent())) {
      return NextResponse.json({ error: 'ai_consent_required' }, { status: 403 })
    }

    const userSettings = await getAISettings(session.user.id)
    if (userSettings.paragraphRefactor === false) {
      return NextResponse.json({ error: 'Feature disabled' }, { status: 403 })
    }

    const body = await request.json()
    const noteId = typeof body.noteId === 'string' ? body.noteId : ''
    const count = typeof body.count === 'number' ? body.count : 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 required' }, { status: 400 })
    }

    const note = await prisma.note.findFirst({
      where: { id: noteId, userId: session.user.id, trashedAt: null },
      select: { id: true, title: true, content: true, language: true },
    })
    if (!note) {
      return NextResponse.json({ error: 'Note not found' }, { status: 404 })
    }

    const textContent = stripHtmlToText(note.content)
    if (textContent.length < 80) {
      return NextResponse.json({ error: 'Not enough content to generate flashcards' }, { status: 400 })
    }

    try {
      await reserveUsageOrThrow(session.user.id, 'ai_flashcard')
    } catch (err) {
      if (err instanceof QuotaExceededError) {
        const isTierLocked = err.currentQuota === 0
        return NextResponse.json({
          error: isTierLocked ? 'feature_locked' : 'quota_exceeded',
          errorKey: isTierLocked ? 'ai.featureLocked' : 'ai.quotaExceeded',
          quotaExceeded: true,
        }, { status: 402 })
      }
      throw err
    }

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


    return NextResponse.json({ cards, noteId: note.id, style })
  } catch (error) {
    console.error('[flashcards/generate]', error)
    const message = error instanceof Error ? error.message : 'Generation failed'
    return NextResponse.json({ error: message }, { status: 500 })
  }
}