import { and, eq } from 'drizzle-orm'
import { useDb } from '../../../../database/client'
import { expenseParticipants, expenses } from '../../../../database/schema'

export default defineEventHandler(async (event) => {
  const slug = getRouterParam(event, 'slug')!
  const id = Number(getRouterParam(event, 'id'))
  await getPotOrThrow(slug)

  const body = await readBody(event)
  const description = typeof body?.description === 'string' ? body.description.trim() : ''
  const amountCents = Number(body?.amountCents)
  const payerId = Number(body?.payerId)
  const participantIds: number[] = Array.isArray(body?.participantIds) ? body.participantIds.map(Number) : []

  if (!description) {
    throw createError({ statusCode: 400, statusMessage: 'description is required' })
  }
  if (!Number.isInteger(amountCents) || amountCents <= 0) {
    throw createError({ statusCode: 400, statusMessage: 'amountCents must be a positive integer' })
  }
  if (participantIds.length === 0) {
    throw createError({ statusCode: 400, statusMessage: 'at least one participant must be selected' })
  }

  const potParticipants = await getParticipants(slug)
  const validIds = new Set(potParticipants.map(p => p.id))
  if (!validIds.has(payerId) || participantIds.some(pid => !validIds.has(pid))) {
    throw createError({ statusCode: 400, statusMessage: 'payerId and participantIds must reference participants of this Pot' })
  }

  const db = useDb()
  const [existing] = await db.select().from(expenses).where(and(eq(expenses.id, id), eq(expenses.potSlug, slug)))
  if (!existing) {
    throw createError({ statusCode: 404, statusMessage: 'Expense not found' })
  }

  await db.update(expenses).set({ description, amountCents, payerId }).where(eq(expenses.id, id))
  await db.delete(expenseParticipants).where(eq(expenseParticipants.expenseId, id))
  await db.insert(expenseParticipants).values(participantIds.map(participantId => ({ expenseId: id, participantId })))

  return { id, description, amountCents, payerId, participantIds }
})