feat(geom): add asPolyline() multi-fn

packages/geom/src/index.ts

@@ -20,6 +20,7 @@ export * from "./ops/arc-length";
 export * from "./ops/area";
 export * from "./ops/as-cubic";
 export * from "./ops/as-polygon";
+export * from "./ops/as-polyline";
 export * from "./ops/as-svg";
 export * from "./ops/bounds";
 export * from "./ops/center";

packages/geom/src/ops/as-polyline.ts

@@ -0,0 +1,44 @@
+import { defmulti, MultiFn1O } from "@thi.ng/defmulti";
+import {
+    IShape,
+    Polyline,
+    SamplingOpts,
+    Type,
+    Path
+} from "../api";
+import { dispatch } from "../internal/dispatch";
+import { vertices } from "./vertices";
+
+export const asPolyline: MultiFn1O<IShape, number | Partial<SamplingOpts>, Polyline> = defmulti(dispatch);
+
+asPolyline.addAll({
+
+    [Type.POINTS]:
+        ($, opts) => new Polyline(vertices($, opts), { ...$.attribs }),
+
+    [Type.PATH]:
+        ($: Path, opts) => {
+            const pts = vertices($, opts);
+            return new Polyline(
+                $.closed ?
+                    pts.concat([pts[0]]) :
+                    pts,
+                { ...$.attribs }
+            );
+        },
+
+    [Type.POLYGON]:
+        ($, opts) => {
+            const pts = vertices($, opts);
+            return new Polyline(pts.concat([pts[0]]), { ...$.attribs });
+        },
+
+});
+
+asPolyline.isa(Type.CIRCLE, Type.POLYGON);
+asPolyline.isa(Type.ELLIPSE, Type.POLYGON);
+asPolyline.isa(Type.LINE, Type.POINTS);
+asPolyline.isa(Type.POLYLINE, Type.POINTS);
+asPolyline.isa(Type.QUAD, Type.POLYGON);
+asPolyline.isa(Type.RECT, Type.POLYGON);
+asPolyline.isa(Type.TRIANGLE, Type.POLYGON);