Feature: allow to move and snap to a layer, fix #2120

src/Logic/Osm/Actions/InsertPointIntoWayAction.ts

@@ -0,0 +1,96 @@
+import { ChangeDescription } from "./ChangeDescription"
+import { GeoOperations } from "../../GeoOperations"
+import { OsmWay } from "../OsmObject"
+
+export default class InsertPointIntoWayAction  {
+    private readonly _lat: number
+    private readonly _lon: number
+    private readonly _idToInsert: number
+    private readonly _snapOnto: OsmWay
+    private readonly _options: {
+        allowReuseOfPreviouslyCreatedPoints?: boolean
+        reusePointWithinMeters?: number
+    }
+
+    constructor(
+        lat: number,
+        lon: number,
+        idToInsert: number,
+        snapOnto: OsmWay,
+        options: {
+            allowReuseOfPreviouslyCreatedPoints?: boolean
+            reusePointWithinMeters?: number
+        }
+    ){
+        this._lat = lat
+        this._lon = lon
+        this._idToInsert = idToInsert
+        this._snapOnto = snapOnto
+        this._options = options
+
+    }
+
+    /**
+     * Tries to create the changedescription of the way where the point is inserted
+     * Returns `undefined` if inserting failed
+     */
+    public prepareChangeDescription():  Omit<ChangeDescription, "meta"> | undefined {
+
+
+        // Project the point onto the way
+        console.log("Snapping a node onto an existing way...")
+        const geojson = this._snapOnto.asGeoJson()
+        const projected = GeoOperations.nearestPoint(GeoOperations.outerRing(geojson), [
+            this._lon,
+            this._lat,
+        ])
+        const projectedCoor = <[number, number]>projected.geometry.coordinates
+        const index = projected.properties.index
+        console.log("Attempting to snap:", { geojson, projected, projectedCoor, index })
+        // We check that it isn't close to an already existing point
+        let reusedPointId = undefined
+        let reusedPointCoordinates: [number, number] = undefined
+        let outerring: [number, number][]
+
+        if (geojson.geometry.type === "LineString") {
+            outerring = <[number, number][]>geojson.geometry.coordinates
+        } else if (geojson.geometry.type === "Polygon") {
+            outerring = <[number, number][]>geojson.geometry.coordinates[0]
+        }
+
+        const prev = outerring[index]
+        if (GeoOperations.distanceBetween(prev, projectedCoor) < this._options.reusePointWithinMeters) {
+            // We reuse this point instead!
+            reusedPointId = this._snapOnto.nodes[index]
+            reusedPointCoordinates = this._snapOnto.coordinates[index]
+        }
+        const next = outerring[index + 1]
+        if (GeoOperations.distanceBetween(next, projectedCoor) < this._options.reusePointWithinMeters) {
+            // We reuse this point instead!
+            reusedPointId = this._snapOnto.nodes[index + 1]
+            reusedPointCoordinates = this._snapOnto.coordinates[index + 1]
+        }
+        if (reusedPointId !== undefined) {
+            return undefined
+        }
+
+        const locations = [
+            ...this._snapOnto.coordinates?.map(([lat, lon]) => <[number, number]>[lon, lat]),
+        ]
+        const ids = [...this._snapOnto.nodes]
+
+        locations.splice(index + 1, 0, [this._lon, this._lat])
+        ids.splice(index + 1, 0, this._idToInsert)
+
+        return  {
+            type: "way",
+            id: this._snapOnto.id,
+            changes: {
+                coordinates: locations,
+                nodes: ids,
+            }
+        }
+
+    }
+
+}