import type { RsvpStatus } from '@prisma/client';

export type ParsedSmsRsvpReply = { status: RsvpStatus; numGuests: number };

const YES_WORDS = new Set(['yes', 'y', 'yep', 'yeah', 'yup', 'ya']);
const NO_WORDS = new Set(['no', 'n', 'nope', 'nah']);
const MAYBE_WORDS = new Set(['maybe', 'perhaps', 'unsure', 'tentative', 'possibly']);

/**
 * Parses a guest's free-form SMS reply into an RSVP status plus an optional
 * guest count (e.g. "YES 3", "no", "Maybe, 2 people"). Only the first word is
 * used to determine status - guests reply in all kinds of phrasing, but the
 * status word almost always leads. Returns null when no recognized status
 * word is found, so the caller can ask the guest to try again.
 */
export function parseSmsRsvpReply(rawBody: string): ParsedSmsRsvpReply | null {
  const body = rawBody.trim();
  if (!body) return null;

  const firstWord = body.toLowerCase().match(/[a-z']+/)?.[0];
  if (!firstWord) return null;

  let status: RsvpStatus;
  if (YES_WORDS.has(firstWord)) status = 'YES';
  else if (NO_WORDS.has(firstWord)) status = 'NO';
  else if (MAYBE_WORDS.has(firstWord)) status = 'MAYBE';
  else return null;

  const countMatch = body.match(/\d+/);
  const numGuests = countMatch ? Math.min(Math.max(parseInt(countMatch[0], 10), 1), 50) : 1;

  return { status, numGuests };
}