+from pathlib import Path
+import os
+
+class GeometryFactory:
+ """ Provides functions to create geometries from scenes and data grids.
+ """
+
+ def __init__(self):
+ defpath = Path(__file__) / '..' / '..' / '..' / 'scenes' / 'data'
+ self.scene_path = os.environ.get('SCENE_PATH', defpath.resolve())
+ self.scene_cache = {}
+ self.clear_grid()
+
+ def parse_geometry(self, geom, scene):
+ """ Create a WKT SQL term for the given geometry.
+ The function understands the following formats:
+
+ [<scene>]:<name>
+ Geometry from a scene. If the scene is omitted, use the
+ default scene.
+ <P>
+ Point geometry
+ <P>,...,<P>
+ Line geometry
+ (<P>,...,<P>)
+ Polygon geometry
+
+ <P> may either be a coordinate of the form '<x> <y>' or a single
+ number. In the latter case it must refer to a point in
+ a previously defined grid.
+ """
+ if geom.find(':') >= 0:
+ return "ST_SetSRID({}, 4326)".format(self.get_scene_geometry(scene, geom))
+
+ if geom.find(',') < 0:
+ out = "POINT({})".format(self.mk_wkt_point(geom))
+ elif geom.find('(') < 0:
+ out = "LINESTRING({})".format(self.mk_wkt_points(geom))
+ else:
+ out = "POLYGON(({}))".format(self.mk_wkt_points(geom.strip('() ')))
+
+ return "ST_SetSRID('{}'::geometry, 4326)".format(out)
+
+ def mk_wkt_point(self, point):
+ """ Parse a point description.
+ The point may either consist of 'x y' cooordinates or a number
+ that refers to a grid setup.
+ """
+ geom = point.strip()
+ if geom.find(' ') >= 0:
+ return geom
+
+ try:
+ pt = self.grid_node(int(geom))
+ except ValueError:
+ assert False, "Scenario error: Point '{}' is not a number".format(geom)
+
+ assert pt is not None, "Scenario error: Point '{}' not found in grid".format(geom)
+ return "{} {}".format(*pt)
+
+ def mk_wkt_points(self, geom):
+ """ Parse a list of points.
+ The list must be a comma-separated list of points. Points
+ in coordinate and grid format may be mixed.
+ """
+ return ','.join([self.mk_wkt_point(x) for x in geom.split(',')])
+
+ def get_scene_geometry(self, default_scene, name):
+ """ Load the geometry from a scene.
+ """
+ geoms = []
+ for obj in name.split('+'):
+ oname = obj.strip()
+ if oname.startswith(':'):
+ assert default_scene is not None, "Scenario error: You need to set a scene"
+ defscene = self.load_scene(default_scene)
+ wkt = defscene[oname[1:]]
+ else:
+ scene, obj = oname.split(':', 2)
+ scene_geoms = self.load_scene(scene)
+ wkt = scene_geoms[obj]
+
+ geoms.append("'{}'::geometry".format(wkt))
+
+ if len(geoms) == 1:
+ return geoms[0]
+
+ return 'ST_LineMerge(ST_Collect(ARRAY[{}]))'.format(','.join(geoms))
+
+ def load_scene(self, name):
+ """ Load a scene from a file.
+ """
+ if name in self.scene_cache:
+ return self.scene_cache[name]
+
+ scene = {}
+ with open(Path(self.scene_path) / "{}.wkt".format(name), 'r') as fd:
+ for line in fd:
+ if line.strip():
+ obj, wkt = line.split('|', 2)
+ scene[obj.strip()] = wkt.strip()
+ self.scene_cache[name] = scene
+
+ return scene
+
+ def clear_grid(self):
+ self.grid = {}
+
+ def add_grid_node(self, nodeid, x, y):
+ self.grid[nodeid] = (x, y)
+
+ def grid_node(self, nodeid):
+ return self.grid.get(nodeid)