import { NextRequest, NextResponse } from 'next/server'
import { auth } from '@/auth'
import { mathFromTextService } from '@/lib/ai/services/math-from-text.service'
import { reserveUsageOrThrow, QuotaExceededError } from '@/lib/entitlements'

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

    const { description } = await request.json()
    if (!description || typeof description !== 'string' || !description.trim()) {
      return NextResponse.json({ error: 'Description is required' }, { status: 400 })
    }

    try {
      await reserveUsageOrThrow(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', upgradeTier: err.upgradeTier, quotaExceeded: true },
          { status: 402 },
        )
      }
      throw err
    }

    const latex = await mathFromTextService.generate(description)

    return NextResponse.json({ latex })
  } catch (error: any) {
    return NextResponse.json({ error: error.message || 'Failed to generate LaTeX' }, { status: 500 })
  }
}