import { NextRequest, NextResponse } from 'next/server'
import { auth } from '@/auth'
import prisma from '@/lib/prisma'
import { exerciseGeneratorService } from '@/lib/ai/services/exercise-generator.service'
import { checkEntitlementOrThrow, QuotaExceededError, incrementUsageAsync } from '@/lib/entitlements'
import { preprocessMathInHtml } from '@/lib/text/math-preprocess'

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

    const { noteId, count, language } = await request.json()
    if (!noteId) {
      return NextResponse.json({ error: 'noteId is required' }, { status: 400 })
    }

    try {
      await checkEntitlementOrThrow(session.user.id, 'reformulate')
    } 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' },
          { status: 402 },
        )
      }
      throw err
    }

    const note = await prisma.note.findUnique({
      where: { id: noteId },
      select: { id: true, title: true, content: true, notebookId: true },
    })

    if (!note) {
      return NextResponse.json({ error: 'Note not found' }, { status: 404 })
    }

    const exercises = await exerciseGeneratorService.generate(
      note.title || 'Sans titre',
      note.content,
      { count: count || 5, language: language || 'fr' }
    )

    // Create exercise notes in the same notebook
    const lang = language || 'fr'
    const exerciseLabel = lang === 'fr' ? 'Exercice' : lang === 'fa' ? 'تمرین' : 'Exercise'
    const answerLabel = lang === 'fr' ? 'Corrigé' : lang === 'fa' ? 'پاسخ' : 'Answer'

    const createdNotes = []
    for (let i = 0; i < exercises.length; i++) {
      const ex = exercises[i]
      const difficultyEmoji = ex.difficulty === 'facile' ? '🟢' : ex.difficulty === 'moyen' ? '🟡' : '🔴'

      const rawContent = `
<div data-type="callout-block" data-callout-type="warning"><p><strong>${exerciseLabel} ${i + 1}</strong> — ${difficultyEmoji} ${ex.difficulty}</p></div>
<h2>Énoncé</h2>
<p>${ex.question}</p>
<div data-type="toggle-block" data-opened="false"><p><strong>${answerLabel}</strong> — cliquer pour révéler</p><h3>Solution</h3><p>${ex.answer}</p></div>
`.trim()

      const content = preprocessMathInHtml(rawContent)

      const created = await prisma.note.create({
        data: {
          title: `${exerciseLabel} ${i + 1} — ${note.title || ''}`,
          content,
          userId: session.user.id,
          notebookId: note.notebookId,
          type: 'richtext',
          order: 999 + i,
        },
      })
      createdNotes.push(created)

      void (async () => {
        try {
          const { embeddingService } = await import('@/lib/ai/services/embedding.service')
          const { upsertNoteEmbedding } = await import('@/lib/embeddings')
          const { chunkIndexingService } = await import('@/lib/ai/services/chunk-indexing.service')
          const { embedding } = await embeddingService.generateNoteEmbedding(created.title, content)
          await upsertNoteEmbedding(created.id, embedding)
          await chunkIndexingService.indexNote(created.id, created.title, content)
        } catch {}
      })()
    }

    incrementUsageAsync(session.user.id, 'reformulate')

    return NextResponse.json({
      exercises: createdNotes.map(n => ({ id: n.id, title: n.title })),
    })
  } catch (error: any) {
    console.error('[Exercise Generator] Error:', error)
    return NextResponse.json({ error: error.message || 'Failed to generate exercises' }, { status: 500 })
  }
}