import { useDb } from '~~/server/database/client'
import { expenseParticipants, expenses } from '~~/server/database/schema'

export default defineEventHandler(async (event) => {
  const slug = getRouterParam(event, 'slug')!
  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(id => !validIds.has(id))) {
    throw createError({ statusCode: 400, statusMessage: 'payerId and participantIds must reference participants of this Pot' })
  }

  const db = useDb()
  const [expense] = await db.insert(expenses).values({ potSlug: slug, description, amountCents, payerId }).returning()
  await db.insert(expenseParticipants).values(participantIds.map(participantId => ({ expenseId: expense!.id, participantId })))

  return { ...expense, participantIds }
})