Added Triangulator interface as per #23

planar/triangulate/triangulate.go

@@ -0,0 +1,43 @@
+package triangulate
+
+import (
+	"context"
+
+	"github.com/go-spatial/geom"
+)
+
+type nodata struct{}
+
+// EmptyMetadata can be used to indicate that this point or line does
+// not have any metadata associated with it.
+var EmptyMetadata = nodata{}
+
+// Triangulator describes an object that can take a set of points and produce
+// a triangulation.
+type Triangulator interface {
+
+	// SetPoints sets the nodes to be used in the triangulations
+	// the number of data elements should be equal to or less then
+	// the number of the points, where the index of the data maps
+	// to the point. The EmptyMetadata value can be used to indicate no metadata
+	// for that point.
+	SetPoints(ctx context.Context, pts []geom.Point, data []interface{})
+
+	// Triangles returns the triangles that were produced by the triangulation
+	// If the triangulation uses a frame the includeFrame should be used to
+	// determine if the triangles touching the frame should be included or not.
+	Triangles(ctx context.Context, includeFrame bool) []geom.Triangle
+}
+
+// Constrainer is a Triangulator that can take set of points and ensure that the
+// given set of edges (the constraints) exist in the triangulation.
+type Constrainer interface {
+	Triangulator
+
+	// AddConstraints adds constraint lines to the triangulation, this may require
+	// the triangulation to be recalculated.
+	// Data is any matadata to be attached to each constraint. The number of data
+	// elements must be less then the number of lines. The EmptyMetadata value can be used to
+	// indicate no metadata for that constraint.
+	AddConstraint(ctx context.Context, constraints []geom.Line, data []interface{}) error
+}