import { NextRequest, NextResponse } from 'next/server'
import { auth } from '@/auth'
import prisma from '@/lib/prisma'
import { studyPlannerService } from '@/lib/ai/services/study-planner.service'
import { checkEntitlementOrThrow, QuotaExceededError, incrementUsageAsync } 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 { notebookId, examDate } = await request.json()
    if (!notebookId || !examDate) {
      return NextResponse.json({ error: 'notebookId and examDate are 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 notes = await prisma.note.findMany({
      where: { notebookId, trashedAt: null, userId: session.user.id },
      select: { id: true, title: true },
      orderBy: { order: 'asc' },
    })

    if (notes.length === 0) {
      return NextResponse.json({ error: 'No notes found in notebook' }, { status: 400 })
    }

    const userLang = await prisma.user.findUnique({
      where: { id: session.user.id },
      select: { theme: true },
    })

    const plan = await studyPlannerService.generate(notes, examDate)

    // Set reminders on notes based on the plan
    for (const day of plan.days) {
      for (const noteId of day.noteIds) {
        try {
          const reminderDate = new Date(day.date)
          reminderDate.setHours(9, 0, 0, 0)
          await prisma.note.update({
            where: { id: noteId },
            data: { reminder: reminderDate },
          })
        } catch {}
      }
    }

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

    return NextResponse.json(plan)
  } catch (error: any) {
    console.error('[Study Planner] Error:', error)
    return NextResponse.json({ error: error.message || 'Failed to generate study plan' }, { status: 500 })
  }
}