CREATE TABLE bell_events (
    id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
    producer_id text NOT NULL,
    source_event_id text NOT NULL,
    event_type text NOT NULL,
    occurred_at timestamptz NOT NULL,
    location text NOT NULL,
    severity text NOT NULL CHECK (severity IN ('low','medium','high','critical')),
    evidence_ref text,
    normalized_payload jsonb NOT NULL,
    payload_sha256 bytea NOT NULL,
    created_at timestamptz NOT NULL DEFAULT now(),
    UNIQUE (producer_id, source_event_id)
);
CREATE INDEX bell_events_created_page_idx ON bell_events(created_at DESC,id DESC);
CREATE TABLE bell_event_receipts (
    id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
    event_id uuid NOT NULL UNIQUE REFERENCES bell_events(id),
    producer_id text NOT NULL,
    source_event_id text NOT NULL,
    payload_sha256 bytea NOT NULL,
    accepted_at timestamptz NOT NULL DEFAULT now(),
    UNIQUE (producer_id, source_event_id)
);

CREATE OR REPLACE FUNCTION bell_reject_event_mutation() RETURNS trigger LANGUAGE plpgsql AS $$
BEGIN RAISE EXCEPTION 'Bell Event and Receipt facts are immutable'; END $$;
CREATE TRIGGER bell_event_no_update BEFORE UPDATE OR DELETE ON bell_events FOR EACH ROW EXECUTE FUNCTION bell_reject_event_mutation();
CREATE TRIGGER bell_receipt_no_update BEFORE UPDATE OR DELETE ON bell_event_receipts FOR EACH ROW EXECUTE FUNCTION bell_reject_event_mutation();