import { and, eq } from 'drizzle-orm';
import { useDb } from '~~/server/database/client';
import { expenseParticipants, expenses } from '~~/server/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(event);
  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 };
});