tile38/geojson/polygon.go

package geojson

import (
	"bytes"
	"strconv"

	"github.com/tidwall/tile38/geojson/geohash"
)

// Polygon is a geojson object with the type "Polygon"
type Polygon struct {
	Coordinates [][]Position
	BBox        *BBox
}

func fillPolygon(coordinates [][]Position, bbox *BBox, err error) (Polygon, error) {
	if err == nil {
		if len(coordinates) == 0 {
			err = errMustBeALinearRing
		}
	}
	if err == nil {
		for _, ps := range coordinates {
			if !isLinearRing(ps) {
				err = errMustBeALinearRing
				break
			}
		}
	}
	return Polygon{
		Coordinates: coordinates,
		BBox:        bbox,
	}, err
}

// CalculatedBBox is exterior bbox containing the object.
func (g Polygon) CalculatedBBox() BBox {
	return level3CalculatedBBox(g.Coordinates, g.BBox, true)
}

// CalculatedPoint is a point representation of the object.
func (g Polygon) CalculatedPoint() Position {
	return g.CalculatedBBox().center()
}

// Geohash converts the object to a geohash value.
func (g Polygon) Geohash(precision int) (string, error) {
	p := g.CalculatedPoint()
	return geohash.Encode(p.Y, p.X, precision)
}

// PositionCount return the number of coordinates.
func (g Polygon) PositionCount() int {
	return level3PositionCount(g.Coordinates, g.BBox)
}

// Weight returns the in-memory size of the object.
func (g Polygon) Weight() int {
	return level3Weight(g.Coordinates, g.BBox)
}

// MarshalJSON allows the object to be encoded in json.Marshal calls.
func (g Polygon) MarshalJSON() ([]byte, error) {
	return []byte(g.JSON()), nil
}

// JSON is the json representation of the object. This might not be exactly the same as the original.
func (g Polygon) JSON() string {
	return level3JSON("Polygon", g.Coordinates, g.BBox)
}

// String returns a string representation of the object. This might be JSON or something else.
func (g Polygon) String() string {
	return g.JSON()
}

func (g Polygon) bboxPtr() *BBox {
	return g.BBox
}
func (g Polygon) hasPositions() bool {
	if g.BBox != nil {
		return true
	}
	for _, c := range g.Coordinates {
		if len(c) > 0 {
			return true
		}
	}
	return false
}

// WithinBBox detects if the object is fully contained inside a bbox.
func (g Polygon) WithinBBox(bbox BBox) bool {
	if g.BBox != nil {
		return rectBBox(g.CalculatedBBox()).InsideRect(rectBBox(bbox))
	}
	if len(g.Coordinates) == 0 {
		return false
	}
	return polyPositions(g.Coordinates[0]).InsideRect(rectBBox(bbox))
}

// IntersectsBBox detects if the object intersects a bbox.
func (g Polygon) IntersectsBBox(bbox BBox) bool {
	if g.BBox != nil {
		return rectBBox(g.CalculatedBBox()).IntersectsRect(rectBBox(bbox))
	}
	if len(g.Coordinates) == 0 {
		return false
	}
	return polyPositions(g.Coordinates[0]).IntersectsRect(rectBBox(bbox))
}

// Within detects if the object is fully contained inside another object.
func (g Polygon) Within(o Object) bool {
	return withinObjectShared(g, o,
		func(v Polygon) bool {
			if len(g.Coordinates) == 0 {
				return false
			}
			return polyPositions(g.Coordinates[0]).Inside(polyExteriorHoles(v.Coordinates))
		},
		func(v MultiPolygon) bool {
			if len(g.Coordinates) == 0 {
				return false
			}
			for _, c := range v.Coordinates {
				if !polyPositions(g.Coordinates[0]).Inside(polyExteriorHoles(c)) {
					return false
				}
			}
			return true
		},
	)
}

// Intersects detects if the object intersects another object.
func (g Polygon) Intersects(o Object) bool {
	return intersectsObjectShared(g, o,
		func(v Polygon) bool {
			if len(g.Coordinates) == 0 {
				return false
			}
			return polyPositions(g.Coordinates[0]).Intersects(polyExteriorHoles(v.Coordinates))
		},
		func(v MultiPolygon) bool {
			if len(g.Coordinates) == 0 {
				return false
			}
			for _, c := range v.Coordinates {
				if polyPositions(g.Coordinates[0]).Intersects(polyExteriorHoles(c)) {
					return true
				}
			}
			return false
		},
	)
}

// Nearby detects if the object is nearby a position.
func (g Polygon) Nearby(center Position, meters float64) bool {
	return nearbyObjectShared(g, center.X, center.Y, meters)
}

// KML outputs kml
func (g Polygon) KML() string {
	var buf bytes.Buffer
	buf.WriteString(`<?xml version="1.0" encoding="UTF-8"?>`)
	buf.WriteString(`<kml xmlns="http://www.opengis.net/kml/2.2">`)
	buf.WriteString(`<Placemark>`)
	buf.WriteString(`<Polygon>`)
	buf.WriteString(`<extrude>1</extrude>`)
	buf.WriteString(`<altitudeMode>relativeToGround</altitudeMode>`)
	for i, c := range g.Coordinates {
		if i == 0 {
			buf.WriteString(`<outerBoundaryIs>`)
		} else {
			buf.WriteString(`<innerBoundaryIs>`)
		}
		buf.WriteString(`<LinearRing>`)
		buf.WriteString(`<coordinates>`)
		for _, c := range c {
			buf.WriteString("\n" + strconv.FormatFloat(c.X, 'f', -1, 64) + `,` + strconv.FormatFloat(c.Y, 'f', -1, 64) + `,` + strconv.FormatFloat(c.Z, 'f', -1, 64))
		}
		if len(c) > 0 {
			buf.WriteString("\n")
		}
		buf.WriteString(`</coordinates>`)
		buf.WriteString(`</LinearRing>`)
		if i == 0 {
			buf.WriteString(`</outerBoundaryIs>`)
		} else {
			buf.WriteString(`</innerBoundaryIs>`)
		}
	}
	buf.WriteString(`</Polygon>`)
	buf.WriteString(`</Placemark>`)
	buf.WriteString(`</kml>`)
	return buf.String()
}

// IsBBoxDefined returns true if the object has a defined bbox.
func (g Polygon) IsBBoxDefined() bool {
	return g.BBox != nil
}

// IsGeometry return true if the object is a geojson geometry object. false if it something else.
func (g Polygon) IsGeometry() bool {
	return true
}