-- Realtime leerlingactiviteit: een sessie start pas bij echte interactie met
-- een toegewezen widget. Heartbeats houden de sessie live; afgesloten en
-- weggevallen sessies blijven kort terug te zien in het klasdashboard.
CREATE TABLE IF NOT EXISTS live_learning_sessions (
  id BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  pupil_id BIGINT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  teacher_id BIGINT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  class_id BIGINT NOT NULL REFERENCES classes(id) ON DELETE CASCADE,
  assignment_id BIGINT REFERENCES assignments(id) ON DELETE SET NULL,
  board_id TEXT NOT NULL,
  widget_id TEXT NOT NULL,
  widget_type TEXT NOT NULL,
  mode TEXT NOT NULL DEFAULT 'werken' CHECK (mode IN ('werken', 'kijken')),
  started_at TIMESTAMPTZ NOT NULL DEFAULT now(),
  last_seen_at TIMESTAMPTZ NOT NULL DEFAULT now(),
  ended_at TIMESTAMPTZ,
  progress_count INTEGER NOT NULL DEFAULT 0,
  attempts INTEGER NOT NULL DEFAULT 0,
  correct INTEGER NOT NULL DEFAULT 0
);

CREATE INDEX IF NOT EXISTS idx_live_learning_sessions_class_recent
  ON live_learning_sessions (class_id, started_at DESC);
CREATE INDEX IF NOT EXISTS idx_live_learning_sessions_pupil_open
  ON live_learning_sessions (pupil_id, ended_at, last_seen_at DESC);