-- Fix Race Condition in Member ID Generation
-- ============================================
-- Problem: Current implementation uses MAX() or COUNT() which allows duplicate IDs
-- if two registrations happen simultaneously.
--
-- Solution: Use PostgreSQL sequence for atomic ID generation.

-- Step 1: Create sequence for member IDs
-- Find the highest existing member number to set starting point
DO $$
DECLARE
  max_num INTEGER;
BEGIN
  -- Extract numeric part from existing member_ids (handles both MUSA-XXXX and MUSA-YYYY-XXXX formats)
  SELECT COALESCE(
    MAX(
      CAST(
        SUBSTRING(
          member_id FROM '[0-9]+$'  -- Get trailing digits
        ) AS INTEGER
      )
    ),
    0
  ) INTO max_num
  FROM public.members;

  -- Create sequence starting from next available number
  EXECUTE format('CREATE SEQUENCE IF NOT EXISTS member_id_seq START WITH %s', max_num + 1);
END $$;

-- Step 2: Replace trigger function to use sequence
CREATE OR REPLACE FUNCTION generate_member_id()
RETURNS TRIGGER AS $$
DECLARE
  next_num INTEGER;
  current_year TEXT;
BEGIN
  -- Only generate if member_id is not already set
  IF NEW.member_id IS NOT NULL THEN
    RETURN NEW;
  END IF;

  -- Get next number from sequence (atomic operation)
  next_num := NEXTVAL('member_id_seq');
  current_year := EXTRACT(YEAR FROM CURRENT_DATE)::TEXT;

  -- Format: MUSA-YYYY-XXXX (matches application format)
  NEW.member_id := 'MUSA-' || current_year || '-' || LPAD(next_num::TEXT, 4, '0');

  RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- Step 3: Ensure trigger exists (should already exist from 001_initial_schema.sql)
DROP TRIGGER IF EXISTS set_member_id ON public.members;
CREATE TRIGGER set_member_id
  BEFORE INSERT ON public.members
  FOR EACH ROW
  WHEN (NEW.member_id IS NULL)
  EXECUTE FUNCTION generate_member_id();

-- Step 4: Add index on member_id for faster lookups (if not exists)
CREATE INDEX IF NOT EXISTS idx_members_member_id ON public.members(member_id);

COMMENT ON SEQUENCE member_id_seq IS 'Atomic sequence for generating unique member IDs. Used by generate_member_id() trigger.';
COMMENT ON FUNCTION generate_member_id() IS 'Atomically generates member IDs using NEXTVAL(member_id_seq) to prevent race conditions.';