Layout checkout, fix TODO in Collection

Collection.js

@@ -1,12 +1,12 @@
 class Collection {
   constructor(nodes) {
-    this.nodes = nodes;
+    this.nodes = new Set(nodes);
   }
 
   setTension() {
     this.vec = [0, 0];
     this.tension = 0;
-    for (let node of this.nodes) {
+    for (let node of this.nodes.values()) {
       node.setTension();
       for (let i of [0, 1]) {
         this.vec[i] += node.vec[i];
@@ -16,11 +16,9 @@ class Collection {
   }
 
   offsetCollides(graph, offset) {
-    // TODO: make this.nodes always a set
-    let nodeSet = new Set(this.nodes);
-    for (let node of this.nodes) {
+    for (let node of this.nodes.values()) {
       let other = node.offsetCollides(graph, offset);
-      if (other && !nodeSet.has(other)) {
+      if (other && !this.nodes.has(other)) {
         return other;
       }
     }
@@ -28,19 +26,19 @@ class Collection {
   }
 
   savePos() {
-    for (let node of this.nodes) {
+    for (let node of this.nodes.values()) {
       node.savePos();
     }
   }
 
   restorePos(graph) {
-    for (let node of this.nodes) {
+    for (let node of this.nodes.values()) {
       node.restorePos(graph);
     }
   }
 
   moveBy(graph, offset) {
-    let nodes = new Set(this.nodes);
+    let nodes = new Set(this.nodes.values());
     while (nodes.size) {
       for (let node of nodes) {
         if (node.offsetCollides(graph, offset)) {

Layout.js

@@ -0,0 +1,38 @@
+class Layout {
+  constructor(graph) {
+    this.nodesByPos = new Map();
+
+    this.graph_ = graph;
+
+    this.setInitialPositions();
+  }
+
+  setInitialPositions() {
+    const SPACING = 4;
+
+    let maxRankNodes = 0;
+    for (let nodes of this.graph_.nodesByPageRank.values()) {
+      maxRankNodes = Math.max(maxRankNodes, nodes.length);
+    }
+
+    let ranks = Array.from(this.graph_.nodesByPageRank.keys());
+    ranks.sort((a, b) => a - b);
+    for (let r = 0; r < ranks.length; ++r) {
+      let nodes = this.graph_.nodesByPageRank.get(ranks[r]);
+      for (let n = 0; n < nodes.length; ++n) {
+        let node = nodes[n];
+        let pos = [
+            r * SPACING,
+            Math.floor((nodes.length / 2) * SPACING) + (n * SPACING) +
+                (node.subgraph * SPACING * maxRankNodes),
+        ];
+        node.pos = pos;
+        this.setNodePos(node, pos);
+      }
+    }
+  }
+
+  setNodePos(node, pos) {
+    this.nodesByPos.set(pos.toString(), node);
+  }
+}

render.js

@@ -1,5 +1,7 @@
 function onmessage(def) {
-  new Graph(def);
+  let graph = new Graph(def);
+  let layout = new Layout(graph);
 }
 
 <!--# include file="Graph.js" -->
+<!--# include file="Layout.js" -->