-- 016: username-based first-party auth.
-- Usernames are the login identity (external_id = local:<username>); email is
-- optional metadata for future password recovery. Existing email-keyed users
-- get a username derived from their email local-part (or display name).
ALTER TABLE users ADD COLUMN username text;

UPDATE users SET username = COALESCE(
  NULLIF(regexp_replace(lower(split_part(coalesce(email, ''), '@', 1)), '[^a-z0-9_.-]', '', 'g'), ''),
  NULLIF(regexp_replace(lower(display_name), '[^a-z0-9_.-]', '', 'g'), ''),
  'member'
);
-- Deterministic dedupe: colliding candidates get a short id suffix.
UPDATE users u SET username = u.username || '_' || substr(u.id::text, 1, 4)
WHERE EXISTS (SELECT 1 FROM users v WHERE v.username = u.username AND v.id < u.id);

ALTER TABLE users ALTER COLUMN username SET NOT NULL;
CREATE UNIQUE INDEX users_username_key ON users (username);
ALTER TABLE users ALTER COLUMN email DROP NOT NULL;

GRANT SELECT, INSERT, UPDATE, DELETE ON users TO sp_app;