Began rebuilding computation engine to be dependency graph centric

app/imports/api/creature/computation/newEngine/applyFnToKey.js

@@ -0,0 +1,46 @@
+import { get } from 'lodash';
+
+export function applyFnToKey(doc, key, fn){
+  if (key.includes('$.')){
+    applyToArrayKey(doc, key, fn);
+  } else {
+    applyToSingleKey(doc, key, fn);
+  }
+}
+
+function applyToSingleKey(doc, key, fn){
+  // call the function with the current value and document for context
+  fn(doc, key);
+}
+
+/**
+ * Applies the given function to all instances in a document key
+ * key.$.with.$.subdocs will apply to all key[i...n].with[j...m].subdocs
+ */
+function applyToArrayKey(doc, key, fn){
+  const keySplit = key.split('.$');
+
+  // Stack based depth first traversal of arrays
+  const stack = [{
+    array: get(doc, keySplit[0]),
+    paths: keySplit.slice(1),
+    currentPath: keySplit[0],
+    indices: [],
+  }];
+  while(stack.length){
+    const state = stack.pop();
+    for (let index in state.array.length){
+      const currentPath = `${state.currentPath}[${index}]${state.paths[0]}`
+      if (state.paths.length == 1){
+        applyToSingleKey(doc, currentPath, fn);
+      } else {
+        stack.push({
+          array: get(doc, currentPath),
+          paths: state.paths.slice(1),
+          currentPath,
+          indices: [...state.indices, index],
+        });
+      }
+    }
+  }
+}