-- Check correctness of an hexagons grid
--
-- Cells must have no overlaps and have a number of
-- intersections with other cells between 2 and 6
--

WITH
 params AS ( SELECT ST_MakeEnvelope(10, 10, 20, 20) as env, 2 as radius ),
 grid AS ( SELECT CDB_HexagonGrid(env, radius) AS cell from params),
 igrid AS ( SELECT row_number() over (), cell from grid )

 SELECT count(row_number) as r1, sum(st_npoints(cell)) as r2, 'count / npoints' as err
 FROM igrid g1

UNION ALL

 SELECT g1.row_number as r1, g2.row_number as r2, 'overlap' as err
 FROM igrid g1, igrid g2
 WHERE g2.row_number > g1.row_number AND
       ST_Overlaps(g1.cell, g2.cell)

UNION ALL

 SELECT g1.row_number, count(g2.row_number) as r2, 'n intersections' as err
 FROM igrid g1, igrid g2
 WHERE g1.row_number != g2.row_number AND
       ST_Intersects(g1.cell, g2.cell)
       GROUP BY g1.row_number
       HAVING count(g2.row_number) > 6 OR count(g2.row_number) < 2

UNION ALL

 SELECT g1.row_number, null::integer, 'centroid out of extent' as err
 FROM igrid g1, params
 WHERE NOT ST_Intersects(ST_Centroid(g1.cell), params.env)

	;


-- Check robustness of HexagonGrid generation

WITH
 params AS ( SELECT
 ST_MakeEnvelope(-20037508.5,20037507,-20037508,20037507.5) as env,
 0.002 as radius ),
 grid AS ( SELECT CDB_HexagonGrid(env, radius) AS cell from params)
SELECT '#160', count(cell) > 23000 from grid;