CREATE TYPE closure_result AS (cvterm_id INTEGER, pathdistance INTEGER);

-- results may not be distinct
CREATE OR REPLACE FUNCTION _closure_over_IS_A(INTEGER, INTEGER) RETURNS SETOF INTEGER AS
$$
DECLARE
    term        ALIAS FOR $1;
    is_a_id     ALIAS FOR $2;
    inner_row               RECORD;
    outer_row               RECORD;
BEGIN
    -- get direct is_a parents
    FOR inner_row IN SELECT object_id AS cvterm_id 
                 FROM cvterm_relationship WHERE subject_id = term AND type_id=is_a_id LOOP
        -- return direct is_a parents
        RETURN NEXT inner_row.cvterm_id;

        -- recursive, self-call
        FOR outer_row IN SELECT * FROM _closure_over_IS_A(inner_row.cvterm_id, is_a_id) LOOP
            RETURN NEXT outer_row._closure_over_IS_A;
        END LOOP;
    END LOOP;
    RETURN;
END;
$$
LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION closure_over_IS_A(INTEGER) RETURNS SETOF INTEGER AS
$$
DECLARE
    is_a_id           INTEGER;
    r                 RECORD;
BEGIN
    SELECT INTO is_a_id get_cvterm_id_for_is_a();
    FOR r IN SELECT * FROM  _closure_over_IS_A($1, is_a_id) LOOP
        RETURN NEXT r._closure_over_IS_A;
    END LOOP;
    RETURN;
END;
$$
LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION closure_over_reflexive_IS_A(INTEGER) RETURNS SETOF INTEGER AS
$$
DECLARE
    is_a_id           INTEGER;
    r                 RECORD;
BEGIN
    SELECT INTO is_a_id get_cvterm_id_for_is_a();
    FOR r IN SELECT * FROM  _closure_over_IS_A($1, is_a_id)
             UNION SELECT $1 
           LOOP
        RETURN NEXT r._closure_over_IS_A;
    END LOOP;
    RETURN;
END;
$$
LANGUAGE 'plpgsql';

-- implements:
--  X R Z <= X is_a* Y, Y R Z
-- but not:
--  X R Z <= X R Y, Y is_a+ Z
CREATE OR REPLACE FUNCTION _closure_over_relation_with_dist_partial(INTEGER,INTEGER,INTEGER,INTEGER) RETURNS SETOF closure_result AS
$$
DECLARE
    term                ALIAS FOR $1; 
    relation_id         ALIAS FOR $2;
    is_a_id             ALIAS FOR $3;
    depth               ALIAS FOR $4;
    depth2              INTEGER;
    isa_plus_r          RECORD;
    direct_link_r       closure_result%ROWTYPE;
    trans_link_r        closure_result%ROWTYPE;
BEGIN
    depth2 := depth+1;
    -- get ALL is_a* parents
    FOR isa_plus_r IN SELECT * FROM _closure_over_is_a(term,is_a_id) AS cvterm_id UNION SELECT term AS cvterm_id LOOP

       RAISE NOTICE ''is_a %'', isa_plus_r.cvterm_id;
       FOR direct_link_r IN SELECT object_id AS cvterm_id, depth2 AS pathdistance
                     FROM cvterm_relationship WHERE subject_id = isa_plus_r.cvterm_id AND type_id=relation_id LOOP
           RAISE NOTICE ''obj % dist % / % '', direct_link_r.cvterm_id, depth2, direct_link_r.pathdistance;
           -- return direct R parents
           RETURN NEXT direct_link_r;
           -- recursive, self-call
           FOR trans_link_r IN SELECT *
                 FROM _closure_over_relation_with_dist_partial(direct_link_r.cvterm_id, relation_id, is_a_id, depth2) LOOP
               RETURN NEXT trans_link_r;
           END LOOP;
       END LOOP;
    END LOOP;
    RETURN;
END;
$$
LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION closure_over_relation_with_dist(INTEGER,INTEGER) RETURNS SETOF closure_result AS
$$
DECLARE
    is_a_id           INTEGER;
    r                 closure_result%ROWTYPE;
    r_plus_is_a       closure_result%ROWTYPE;
BEGIN
    SELECT INTO is_a_id get_cvterm_id_for_is_a();
    FOR r IN SELECT * FROM  _closure_over_relation_with_dist_partial($1,$2,is_a_id,0) AS cvterm_id LOOP
       FOR r_plus_is_a IN 
           SELECT cvterm_id, r.pathdistance FROM  _closure_over_is_a(r.cvterm_id,is_a_id) AS cvterm_id
           UNION SELECT r.* LOOP
             RETURN NEXT r_plus_is_a;
       END LOOP;
    END LOOP;
    RETURN;
END;
$$
LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION forward_chain() RETURNS INT AS
$$
DECLARE
  num_assertions        INTEGER;
  total_assertions      INTEGER;
BEGIN
  total_assertions := 0;

  PERFORM seed_cvtermpath();

  -- keep adding new facts until exhausted
  LOOP
    SELECT INTO num_assertions forward_chain_iteration();
    total_assertions := total_assertions + num_assertions;

    RAISE LOG 'Asserted % new facts; current_total=%', num_assertions, total_assertions;
    EXIT WHEN num_assertions > 0;
  END LOOP;   
  RETURN total_assertions;
END;
$$ LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION seed_cvtermpath() RETURNS INT AS
$$
DECLARE
  num_assertions        INTEGER;
  is_a_id               INTEGER;
BEGIN
  RAISE LOG 'Seeding cvtermpath';

  -- seed cvtermpath with direct asserted links
  INSERT INTO cvtermpath 
    (subject_id,type_id,object_id,pathdistance)
    SELECT DISTINCT
      link.subject_id,
      link.type_id,
      link.object_id,
      1
     FROM 
      cvterm_relationship AS link
      LEFT JOIN cvtermpath AS p1 USING (subject_id,type_id,object_id) -- exclude pre-populated links
     WHERE  p1.cvtermpath_id IS NULL; -- this is how we do a SELECT MINUS
  GET DIAGNOSTICS num_assertions = ROW_COUNT;
  RAISE LOG 'Seeded cvtermpath with % links', num_assertions;

  SELECT INTO is_a_id get_cvterm_id_for_is_a();
  -- seed cvtermpath with reflexive is_a
  INSERT INTO cvtermpath 
    (subject_id,type_id,object_id,pathdistance)
    SELECT DISTINCT
      t.cvterm_id,
      is_a_id,
      t.cvterm_id,
      0
     FROM 
      cvterm AS t
      LEFT JOIN cvtermpath AS p1 ON 
        (p1.subject_id=t.cvterm_id,p1.type_id=t.is_a_id,p1.object_id=t.cvterm_id) -- exclude pre-populated links
     WHERE  p1.cvtermpath_id IS NULL; -- this is how we do a SELECT MINUS
  GET DIAGNOSTICS num_assertions = ROW_COUNT;
  RAISE LOG 'Seeded cvtermpath with % links', num_assertions;

  RETURN num_assertions;
END;
$$ LANGUAGE 'plpgsql';

CREATE OR REPLACE FUNCTION forward_chain_iteration() RETURNS INT AS
$$
DECLARE
  num_assertions        INTEGER;
  total_assertions      INTEGER;
BEGIN
  total_assertions := 0;

  -- add your own rules here:
  SELECT INTO num_assertions forward_chain_iteration_rule_is_a();
  total_assertions := total_assertions + num_assertions;
  -- end of rules section

  RETURN total_assertions;
END;
$$ LANGUAGE 'plpgsql';

-- IS_A rule
-- X is_a Y, Y is_a Z => X is_a Z
CREATE OR REPLACE FUNCTION forward_chain_iteration_rule_is_a() RETURNS INT AS
$$
DECLARE
    is_a_id           INTEGER;
    num_assertions    INTEGER;
BEGIN
    RAISE LOG 'Applying rule: IS_A';
    SELECT INTO is_a_id get_cvterm_id_for_is_a();
    INSERT INTO cvtermpath 
      (subject_id,type_id,object_id,pathdistance)
      SELECT DISTINCT
        p.subject_id,
        is_a_id,
        link.object_id,
        p.pathdistance+1
       FROM 
        cvtermpath AS p -- extend this
        INNER JOIN cvterm_relationship AS link ON (p.object_id = link.subject_id) -- using this
        LEFT JOIN cvtermpath AS p1 ON (p1.subject_id=p.subject_id AND p1.object_id=link.object_id AND p1.type_id=is_a_id) -- excluding this [pathdist??]
       WHERE  link.type_id=is_a_id 
         AND  p.type_id=is_a_id 
         AND  p1.cvtermpath_id IS NULL; -- exclude existing paths
     
    GET DIAGNOSTICS num_assertions = ROW_COUNT;
    RAISE LOG 'RULE:IS_A iteration produced % links', num_assertions;
    RETURN num_assertions;
END;
$$ LANGUAGE 'plpgsql';
  
-- TRANSITIVE-OVER-IS_A rule
-- X is_a+ Y, Y R Z => X R Z
CREATE OR REPLACE FUNCTION forward_chain_iteration_rule_trans_over_is_a() RETURNS INT AS
$$
DECLARE
    is_a_id           INTEGER;
    num_assertions    INTEGER;
BEGIN
    RAISE LOG 'Applying rule: TRANS_OVER_IS_A';
    SELECT INTO is_a_id get_cvterm_id_for_is_a();
    INSERT INTO cvtermpath 
      (subject_id,type_id,object_id,pathdistance)
      SELECT DISTINCT
        p_is_a.subject_id,
        p_rel.type_id
        p_rel.object_id,
        p_rel.pathdistance+1
       FROM 
        cvtermpath AS p_is_a  -- extend this
        INNER JOIN cvtermpath AS p_rel ON (p_is_a.object_id = p_rel.subject_id) -- using this
        LEFT JOIN cvtermpath AS p1 ON (p1.subject_id=p_is_a.subject_id AND p1.object_id=p_rel.object_id AND p1.type_id=p_rel.type_id) -- excluding this [pathdist??]
       WHERE  p_is_a.type_id=is_a_id 
         AND  p1.cvtermpath_id IS NULL; -- exclude existing paths
     
    GET DIAGNOSTICS num_assertions = ROW_COUNT;
    RAISE LOG 'Applied rule:TRANS_OVER_IS_A iteration produced % links', num_assertions;
    RETURN num_assertions;
END;
$$ LANGUAGE 'plpgsql';