refactor(es modules): move all files to src, try vite 3.0

src/modules/voronoi.js

@@ -0,0 +1,135 @@
+class Voronoi {
+  /**
+   * Creates a Voronoi diagram from the given Delaunator, a list of points, and the number of points. The Voronoi diagram is constructed using (I think) the {@link https://en.wikipedia.org/wiki/Bowyer%E2%80%93Watson_algorithm |Bowyer-Watson Algorithm}
+   * The {@link https://github.com/mapbox/delaunator/ |Delaunator} library uses {@link https://en.wikipedia.org/wiki/Doubly_connected_edge_list |half-edges} to represent the relationship between points and triangles.
+   * @param {{triangles: Uint32Array, halfedges: Int32Array}} delaunay A {@link https://github.com/mapbox/delaunator/blob/master/index.js |Delaunator} instance.
+   * @param {[number, number][]} points A list of coordinates.
+   * @param {number} pointsN The number of points.
+   */
+  constructor(delaunay, points, pointsN) {
+    this.delaunay = delaunay;
+    this.points = points;
+    this.pointsN = pointsN;
+    this.cells = { v: [], c: [], b: [] }; // voronoi cells: v = cell vertices, c = adjacent cells, b = near-border cell
+    this.vertices = { p: [], v: [], c: [] }; // cells vertices: p = vertex coordinates, v = neighboring vertices, c = adjacent cells
+
+    // Half-edges are the indices into the delaunator outputs:
+    // delaunay.triangles[e] gives the point ID where the half-edge starts
+    // delaunay.halfedges[e] returns either the opposite half-edge in the adjacent triangle, or -1 if there's not an adjacent triangle.
+    for (let e = 0; e < this.delaunay.triangles.length; e++) {
+
+      const p = this.delaunay.triangles[this.nextHalfedge(e)];
+      if (p < this.pointsN && !this.cells.c[p]) {
+        const edges = this.edgesAroundPoint(e);
+        this.cells.v[p] = edges.map(e => this.triangleOfEdge(e));                                   // cell: adjacent vertex
+        this.cells.c[p] = edges.map(e => this.delaunay.triangles[e]).filter(c => c < this.pointsN); // cell: adjacent valid cells
+        this.cells.b[p] = edges.length > this.cells.c[p].length ? 1 : 0;                            // cell: is border
+      }
+
+      const t = this.triangleOfEdge(e);
+      if (!this.vertices.p[t]) {
+        this.vertices.p[t] = this.triangleCenter(t);              // vertex: coordinates
+        this.vertices.v[t] = this.trianglesAdjacentToTriangle(t); // vertex: adjacent vertices
+        this.vertices.c[t] = this.pointsOfTriangle(t);            // vertex: adjacent cells
+      }
+    }
+  }
+
+  /**
+   * Gets the IDs of the points comprising the given triangle. Taken from {@link https://mapbox.github.io/delaunator/#triangle-to-points| the Delaunator docs.}
+   * @param {number} t The index of the triangle
+   * @returns {[number, number, number]} The IDs of the points comprising the given triangle.
+   */
+  pointsOfTriangle(t) {
+    return this.edgesOfTriangle(t).map(edge => this.delaunay.triangles[edge]);
+  }
+
+  /**
+   * Identifies what triangles are adjacent to the given triangle. Taken from {@link https://mapbox.github.io/delaunator/#triangle-to-triangles| the Delaunator docs.}
+   * @param {number} t The index of the triangle
+   * @returns {number[]} The indices of the triangles that share half-edges with this triangle.
+   */
+  trianglesAdjacentToTriangle(t) {
+    let triangles = [];
+    for (let edge of this.edgesOfTriangle(t)) {
+      let opposite = this.delaunay.halfedges[edge];
+      triangles.push(this.triangleOfEdge(opposite));
+    }
+    return triangles;
+  }
+
+  /**
+   * Gets the indices of all the incoming and outgoing half-edges that touch the given point. Taken from {@link https://mapbox.github.io/delaunator/#point-to-edges| the Delaunator docs.}
+   * @param {number} start The index of an incoming half-edge that leads to the desired point
+   * @returns {number[]} The indices of all half-edges (incoming or outgoing) that touch the point.
+   */
+  edgesAroundPoint(start) {
+    const result = [];
+    let incoming = start;
+    do {
+      result.push(incoming);
+      const outgoing = this.nextHalfedge(incoming);
+      incoming = this.delaunay.halfedges[outgoing];
+    } while (incoming !== -1 && incoming !== start && result.length < 20);
+    return result;
+  }
+
+  /**
+   * Returns the center of the triangle located at the given index.
+   * @param {number} t The index of the triangle
+   * @returns {[number, number]}
+   */
+  triangleCenter(t) {
+    let vertices = this.pointsOfTriangle(t).map(p => this.points[p]);
+    return this.circumcenter(vertices[0], vertices[1], vertices[2]);
+  }
+
+  /**
+   * Retrieves all of the half-edges for a specific triangle `t`. Taken from {@link https://mapbox.github.io/delaunator/#edge-and-triangle| the Delaunator docs.}
+   * @param {number} t The index of the triangle
+   * @returns {[number, number, number]} The edges of the triangle.
+   */
+  edgesOfTriangle(t) { return [3 * t, 3 * t + 1, 3 * t + 2]; }
+
+  /**
+   * Enables lookup of a triangle, given one of the half-edges of that triangle. Taken from {@link https://mapbox.github.io/delaunator/#edge-and-triangle| the Delaunator docs.}
+   * @param {number} e The index of the edge
+   * @returns {number} The index of the triangle
+   */
+  triangleOfEdge(e) { return Math.floor(e / 3); }
+
+  /**
+   * Moves to the next half-edge of a triangle, given the current half-edge's index. Taken from {@link https://mapbox.github.io/delaunator/#edge-to-edges| the Delaunator docs.}
+   * @param {number} e The index of the current half edge
+   * @returns {number} The index of the next half edge
+   */
+  nextHalfedge(e) { return (e % 3 === 2) ? e - 2 : e + 1; }
+
+  /**
+   * Moves to the previous half-edge of a triangle, given the current half-edge's index. Taken from {@link https://mapbox.github.io/delaunator/#edge-to-edges| the Delaunator docs.}
+   * @param {number} e The index of the current half edge
+   * @returns {number} The index of the previous half edge
+   */
+  prevHalfedge(e) { return (e % 3 === 0) ? e + 2 : e - 1; }
+
+  /**
+   * Finds the circumcenter of the triangle identified by points a, b, and c. Taken from {@link https://en.wikipedia.org/wiki/Circumscribed_circle#Circumcenter_coordinates| Wikipedia}
+   * @param {[number, number]} a The coordinates of the first point of the triangle
+   * @param {[number, number]} b The coordinates of the second point of the triangle
+   * @param {[number, number]} c The coordinates of the third point of the triangle
+   * @return {[number, number]} The coordinates of the circumcenter of the triangle.
+   */
+  circumcenter(a, b, c) {
+    const [ax, ay] = a;
+    const [bx, by] = b;
+    const [cx, cy] = c;
+    const ad = ax * ax + ay * ay;
+    const bd = bx * bx + by * by;
+    const cd = cx * cx + cy * cy;
+    const D = 2 * (ax * (by - cy) + bx * (cy - ay) + cx * (ay - by));
+    return [
+      Math.floor(1 / D * (ad * (by - cy) + bd * (cy - ay) + cd * (ay - by))),
+      Math.floor(1 / D * (ad * (cx - bx) + bd * (ax - cx) + cd * (bx - ax)))
+    ];
+  }
+}