\set ECHO none
\pset format unaligned
SET search_path TO provsql_test,provsql;

/* The security semiring */
CREATE FUNCTION security_min_state(state classification_level, level classification_level)
  RETURNS classification_level AS
$$
  SELECT CASE WHEN state IS NULL THEN level WHEN state<level THEN state ELSE level END
$$ LANGUAGE SQL IMMUTABLE;

CREATE FUNCTION security_max_state(state classification_level, level classification_level)
  RETURNS classification_level AS
$$
  SELECT CASE WHEN state IS NULL THEN level WHEN state<level THEN level ELSE state END
$$ LANGUAGE SQL IMMUTABLE;

CREATE AGGREGATE security_min(classification_level)
(
  sfunc = security_min_state,
  stype = classification_level,
  initcond = 'top_secret'
);

CREATE AGGREGATE security_max(classification_level)
(
  sfunc = security_max_state,
  stype = classification_level,
  initcond = 'unclassified'
);

CREATE FUNCTION security(token UUID, token2value regclass)
  RETURNS classification_level AS
$$
BEGIN
  RETURN provenance_evaluate(
    token,
    token2value,
    'unclassified'::classification_level,
    'security_min',
    'security_max');
END
$$ LANGUAGE plpgsql PARALLEL SAFE;

/* Example of provenance evaluation */
SELECT create_provenance_mapping('personnel_level', 'personnel', 'classification');
CREATE TABLE result_security AS SELECT
  p1.city,
  security(provenance(),'personnel_level')
FROM personnel p1, personnel p2
WHERE p1.city = p2.city AND p1.id < p2.id
GROUP BY p1.city
ORDER BY p1.city;

SELECT remove_provenance('result_security');
SELECT * FROM result_security;

DROP TABLE result_security;