import { NextResponse } from 'next/server'
import { auth } from '@/lib/auth'
import { prisma } from '@/lib/prisma'
import { updateTransactionSchema } from '@/lib/validations/transaction'

type Params = { params: Promise<{ id: string }> }

export async function PATCH(req: Request, { params }: Params) {
  const session = await auth()
  if (!session?.user?.id) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
  }

  const { id } = await params
  const body = await req.json()
  const parsed = updateTransactionSchema.safeParse(body)
  if (!parsed.success) {
    return NextResponse.json({ error: parsed.error.flatten() }, { status: 400 })
  }

  // Scope check via the account's userId
  const existing = await prisma.transaction.findFirst({
    where: { id, account: { userId: session.user.id } },
  })
  if (!existing) return NextResponse.json({ error: 'Not found' }, { status: 404 })

  // Validate budgetId belongs to this user if provided
  if (parsed.data.budgetId) {
    const budget = await prisma.budget.findFirst({
      where: { id: parsed.data.budgetId, userId: session.user.id },
    })
    if (!budget) return NextResponse.json({ error: 'Budget not found' }, { status: 404 })
  }

  const transaction = await prisma.transaction.update({
    where: { id },
    data: parsed.data,
  })

  return NextResponse.json(transaction)
}