geomfn.go

// Copyright 2020 The Cockroach Authors.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.

// Package geomfn contains functions that are used for geometry-based builtins.
package geomfn

import (
	"github.com/ruiaylin/pgparser/types/geo"
	"github.com/cockroachdb/errors"
	"github.com/twpayne/go-geom"
)

// flattenGeometry flattens a geo.Geometry object.
func flattenGeometry(g *geo.Geometry, emptyBehavior geo.EmptyBehavior) ([]geom.T, error) {
	f, err := g.AsGeomT()
	if err != nil {
		return nil, err
	}
	return flattenGeomT(f, emptyBehavior)
}

// flattenGeomT decomposes geom.T collections to individual geom.T components.
func flattenGeomT(g geom.T, emptyBehavior geo.EmptyBehavior) ([]geom.T, error) {
	if g.Empty() {
		switch emptyBehavior {
		case geo.EmptyBehaviorOmit:
			return nil, nil
		case geo.EmptyBehaviorError:
			return nil, geo.NewEmptyGeometryError()
		default:
			return nil, errors.Newf("programmer error: unknown behavior")
		}
	}
	switch g := g.(type) {
	case *geom.Point:
		return []geom.T{g}, nil
	case *geom.LineString:
		return []geom.T{g}, nil
	case *geom.Polygon:
		return []geom.T{g}, nil
	case *geom.MultiPoint:
		ret := make([]geom.T, g.NumPoints())
		for i := 0; i < g.NumPoints(); i++ {
			ret[i] = g.Point(i)
		}
		return ret, nil
	case *geom.MultiLineString:
		ret := make([]geom.T, g.NumLineStrings())
		for i := 0; i < g.NumLineStrings(); i++ {
			ret[i] = g.LineString(i)
		}
		return ret, nil
	case *geom.MultiPolygon:
		ret := make([]geom.T, g.NumPolygons())
		for i := 0; i < g.NumPolygons(); i++ {
			ret[i] = g.Polygon(i)
		}
		return ret, nil
	case *geom.GeometryCollection:
		ret := make([]geom.T, 0, g.NumGeoms())
		for _, subG := range g.Geoms() {
			if subG.Empty() {
				switch emptyBehavior {
				case geo.EmptyBehaviorOmit:
					continue
				case geo.EmptyBehaviorError:
					return nil, geo.NewEmptyGeometryError()
				default:
					return nil, errors.Newf("programmer error: unknown behavior")
				}
			}
			ret = append(ret, subG)
		}
		return ret, nil
	}
	return nil, errors.Newf("unknown geom: %T", g)
}