big design update, bugs, etc

src/tree.js

@@ -1,5 +1,78 @@
 var VisNode = Backbone.Model.extend({
+  defaults: {
+    id: null,
+    pos: null,
+    commit: null
+  },
+
+  validateAtInit: function() {
+    if (!this.get('id')) {
+      throw new Error('need id for mapping');
+    }
+    if (!this.get('commit')) {
+      throw new Error('need commit for linking');
+    }
+
+    if (!this.get('pos')) {
+      this.set('pos', {
+        x: Math.random(),
+        y: Math.random(),
+      });
+    }
+  },
+
+  initialize: function() {
+    this.validateAtInit();
+  },
+
+  calcPositionInTree: function() {
+
+  },
+
+  getScreenCoords: function() {
+    var pos = this.get('pos');
+    return gitVisuals.toScreenCoords(pos);
+  },
+
+  genGraphics: function(paper) {
+    var pos = this.getScreenCoords();
+    //var circle = paper.circle(pos.x, pos.y, GRAPHICS.nodeRadius);
+    var circle = cuteSmallCircle(paper, pos.x, pos.y, {
+      radius: GRAPHICS.nodeRadius
+    });
+    this.set('circle', circle);
+  }
 });
 
 var VisEdge = Backbone.Model.extend({
+  defaults: {
+    tail: null,
+    head: null
+  },
+
+  validateAtInit: function() {
+    required = ['tail', 'head'];
+    _.each(required, function(key) {
+      if (!this.get(key)) {
+        throw new Error(key + ' is required!');
+      }
+    }, this);
+  },
+
+  initialize: function() {
+    this.validateAtInit();
+  },
+
+  genGraphics: function(paper) {
+    var tailPos = this.get('tail').getScreenCoords();
+    var headPos = this.get('head').getScreenCoords();
+    var pathString = constructPathStringFromCoords([tailPos, headPos]);
+    var path = cutePath(paper, pathString);
+    this.set('path', path);
+  },
+
+});
+
+var VisEdgeCollection = Backbone.Collection.extend({
+  model: VisEdge
 });