-- Add a short human-readable access code to eligible voters for printed notices
ALTER TABLE public.election_eligible_voters
  ADD COLUMN IF NOT EXISTS access_code TEXT;

-- Create a function to generate a unique 6-char alphanumeric code per election
CREATE OR REPLACE FUNCTION public.generate_voter_access_code()
RETURNS TRIGGER
LANGUAGE plpgsql
SECURITY DEFINER
SET search_path = 'public'
AS $$
DECLARE
  new_code TEXT;
  code_exists BOOLEAN;
BEGIN
  LOOP
    new_code := UPPER(SUBSTRING(md5(gen_random_uuid()::text) FROM 1 FOR 6));
    SELECT EXISTS (
      SELECT 1 FROM public.election_eligible_voters
      WHERE election_id = NEW.election_id AND access_code = new_code
    ) INTO code_exists;
    EXIT WHEN NOT code_exists;
  END LOOP;
  NEW.access_code := new_code;
  RETURN NEW;
END;
$$;

-- Auto-generate access codes on insert
CREATE TRIGGER trg_generate_voter_access_code
  BEFORE INSERT ON public.election_eligible_voters
  FOR EACH ROW
  WHEN (NEW.access_code IS NULL)
  EXECUTE FUNCTION public.generate_voter_access_code();

-- Backfill existing voters that have no access code
UPDATE public.election_eligible_voters
SET access_code = UPPER(SUBSTRING(md5(gen_random_uuid()::text || id::text) FROM 1 FOR 6))
WHERE access_code IS NULL;