functions.sql

/* Additional database functions for openstreetmap-carto */

/* Access functions below adapted from https://github.com/imagico/osm-carto-alternative-colors/tree/591c861112b4e5d44badd108f4cd1409146bca0b/sql/roads.sql */

/* Simplified 'yes', 'destination', 'no', 'unrecognised', NULL scale for access restriction 
  'no' is returned if the rendering for highway category does not support 'restricted'.
  NULL is functionally equivalent to 'yes', but indicates the absence of a restriction 
  rather than a positive access = yes. 'unrecognised' corresponds to an uninterpretable 
  access restriction e.g. access=unknown or motorcar=occasionally */
CREATE OR REPLACE FUNCTION carto_int_access(accessvalue text, allow_restricted boolean)
	RETURNS text
	LANGUAGE SQL
	IMMUTABLE PARALLEL SAFE
AS $$
SELECT
	CASE
		WHEN accessvalue IN ('yes', 'designated', 'permissive') THEN 'yes'
		WHEN accessvalue IN ('destination',  'delivery', 'customers') THEN
			CASE WHEN allow_restricted = TRUE  THEN 'restricted' ELSE 'yes' END
		WHEN accessvalue IN ('no', 'permit', 'private', 'agricultural', 'forestry', 'agricultural;forestry') THEN 'no'
		WHEN accessvalue IS NULL THEN NULL
		ELSE 'unrecognised'
	END
$$;

/* Try to promote path to cycleway (if bicycle allowed), then bridleway (if horse)
   This duplicates existing behaviour where designated access is required */
CREATE OR REPLACE FUNCTION carto_path_type(bicycle text, horse text)
	RETURNS text
	LANGUAGE SQL
	IMMUTABLE PARALLEL SAFE
AS $$
SELECT
	CASE
		WHEN bicycle IN ('designated') THEN 'cycleway'
		WHEN horse IN ('designated') THEN 'bridleway'
		ELSE 'path'
	END
$$;

/* Return int_access value which will be used to determine access marking.
   Return values are documented above for carto_int_access function.

   Note that the code handling the promotion of highway=path assumes that
   promotion to cycleway or bridleway is based on the value of bicycle or
   horse respectively. A more general formulation would be, for example,
   WHEN 'cycleway' THEN carto_int_access(COALESCE(NULLIF(bicycle, 'unknown'), "access"), FALSE) */
CREATE OR REPLACE FUNCTION carto_highway_int_access(highway text, "access" text, foot text, bicycle text, horse text, motorcar text, motor_vehicle text, vehicle text)
  RETURNS text
  LANGUAGE SQL
  IMMUTABLE PARALLEL SAFE
AS $$
SELECT
	CASE
		WHEN highway IN ('motorway', 'motorway_link', 'trunk', 'trunk_link', 'primary', 'primary_link', 'secondary',
					 'secondary_link', 'tertiary', 'tertiary_link', 'residential', 'unclassified', 'living_street', 'service', 'road') THEN
			carto_int_access(
				COALESCE(
					NULLIF(motorcar, 'unknown'),
					NULLIF(motor_vehicle, 'unknown'),
					NULLIF(vehicle, 'unknown'),
					"access"), TRUE)
		WHEN highway = 'path' THEN
			CASE carto_path_type(bicycle, horse)
				WHEN 'cycleway' THEN carto_int_access(bicycle, FALSE)
				WHEN 'bridleway' THEN carto_int_access(horse, FALSE)
				ELSE carto_int_access(COALESCE(NULLIF(foot, 'unknown'), "access"), FALSE)
			END
		WHEN highway IN ('pedestrian', 'footway', 'steps') THEN carto_int_access(COALESCE(NULLIF(foot, 'unknown'), "access"), FALSE)
		WHEN highway = 'cycleway' THEN carto_int_access(COALESCE(NULLIF(bicycle, 'unknown'), "access"), FALSE)
		WHEN highway = 'bridleway' THEN carto_int_access(COALESCE(NULLIF(horse, 'unknown'), "access"), FALSE)
		ELSE carto_int_access("access", TRUE)
	END
$$;