-- cohort_instructors — scopes the 'instructor' role to specific cohorts. 'owner' and 'admin'
-- are never checked against this table (they have global teaching visibility by role alone,
-- see src/rbac.js) — this only matters for the plain 'instructor' role.

CREATE TABLE IF NOT EXISTS cohort_instructors (
  cohort_id       TEXT NOT NULL REFERENCES cohorts(cohort_id),
  instructor_id   UUID NOT NULL REFERENCES instructors(instructor_id),
  role_in_cohort  TEXT NOT NULL DEFAULT 'teacher',
  created_at      TIMESTAMPTZ NOT NULL DEFAULT now(),
  PRIMARY KEY (cohort_id, instructor_id)
);

CREATE INDEX IF NOT EXISTS idx_cohort_instructors_instructor ON cohort_instructors(instructor_id);