polygon.go

package basic

import (
	"github.com/terranodo/tegola"
	"github.com/terranodo/tegola/maths"
)

// Polygon describes a basic polygon; made up of multiple lines.
type Polygon []Line

// Just to make basic collection only usable with basic types.
func (Polygon) basicType() {}

// Sublines returns the lines that make up the polygon.
func (p Polygon) Sublines() (slines []tegola.LineString) {
	slines = make([]tegola.LineString, 0, len(p))
	for i := range p {
		slines = append(slines, p[i])
	}
	return slines
}
func (Polygon) String() string {
	return "Polygon"
}

// MultiPolygon describes a set of polygons.
type MultiPolygon []Polygon

// Just to make basic collection only usable with basic types.
func (MultiPolygon) basicType() {}

// Polygons retuns the polygons that make up the set.
func (mp MultiPolygon) Polygons() (polygons []tegola.Polygon) {
	polygons = make([]tegola.Polygon, 0, len(mp))
	for i := range mp {
		polygons = append(polygons, mp[i])
	}
	return polygons
}
func (MultiPolygon) String() string {
	return "MultiPolygon"
}

func NewPolygon(main []maths.Pt, clines ...[]maths.Pt) Polygon {
	p := Polygon{NewLineFromPt(main...)}
	for _, l := range clines {
		p = append(p, NewLineFromPt(l...))
	}
	return p
}
func NewPolygonFromSubLines(lines ...tegola.LineString) (p Polygon) {
	p = make(Polygon, 0, len(lines))
	for i := range lines {
		l := NewLineFromSubPoints(lines[i].Subpoints()...)
		p = append(p, l)
	}
	return p
}

func NewMultiPolygonFromPolygons(polygons ...tegola.Polygon) (mp MultiPolygon) {
	mp = make(MultiPolygon, 0, len(polygons))
	for i := range polygons {
		p := NewPolygonFromSubLines(polygons[i].Sublines()...)
		mp = append(mp, p)
	}
	return mp
}