-- Persistent completion records — stage/curriculum/assessment/capstone. Not a certificate
-- (Phase 4/5 territory, see docs/PHASE3B_LEARNING_AND_ASSESSMENT.md): just the durable fact
-- that something was achieved, with enough context to render a certificate from later without
-- re-deriving it from raw attempt history.

CREATE TABLE IF NOT EXISTS achievements (
  achievement_id           BIGSERIAL PRIMARY KEY,
  student_id                 TEXT NOT NULL REFERENCES students(student_id),
  achievement_type           TEXT NOT NULL CHECK (achievement_type IN
                               ('stage_completed', 'curriculum_completed', 'assessment_completed', 'capstone_completed')),
  curriculum_path_id         TEXT,
  curriculum_version         INTEGER,
  stage_id                    TEXT,
  assessment_session_id       UUID REFERENCES assessment_sessions(assessment_session_id),
  achieved_at                 TIMESTAMPTZ NOT NULL DEFAULT now(),
  metadata                    JSONB
);

CREATE INDEX IF NOT EXISTS idx_achievements_student ON achievements(student_id, achievement_type);