Started restructuring the library with attacks, saves, and limited parenting

app/imports/api/parenting/parenting.js

@@ -1,5 +1,41 @@
 import fetchDocByRef from '/imports/api/parenting/fetchDocByRef.js';
 import getCollectionByName from '/imports/api/parenting/getCollectionByName.js';
+import { flatten } from 'lodash';
+
+const generalParents = [
+  'attribute',
+  'buff',
+  'classLevel',
+  'feature',
+  'folder',
+  'root',
+  'item',
+  'spell',
+];
+
+// Which types are allowed as parents for other types
+const allowedParenting = {
+  folder: [...generalParents, 'container'],
+  rollResult: ['roll', 'rollResult'],
+  container: ['root', 'folder'],
+  item: ['root', 'container', 'folder'],
+};
+
+const allParentTypes = new Set(flatten(Object.values(allowedParenting)));
+
+export function canBeParent(type){
+  return type && allParentTypes.has(type);
+}
+
+export function getAllowedParents({childType}){
+  return allowedParenting[childType] || generalParents;
+}
+
+export function isParentAllowed({parentType = 'root', childType}){
+  if (!childType) throw 'childType is required';
+  let allowedParents = getAllowedParents({childType});
+  return allowedParents.includes(parentType);
+}
 
 export function fetchParent({id, collection}){
   return fetchDocByRef({id, collection});
@@ -55,7 +91,7 @@ export function getAncestry({parentRef, inheritedFields = {}}){
   let ancestors = parentDoc.ancestors || [];
   ancestors.push(parent);
 
-  return {parent, ancestors};
+  return {parentDoc, parent, ancestors};
 }
 
 export function updateParent({docRef, parentRef}){
@@ -63,14 +99,30 @@ export function updateParent({docRef, parentRef}){
   let oldDoc = fetchDocByRef(docRef, {fields: {
     parent: 1,
     ancestors: 1,
+    type: 1,
   }});
   let updateOptions = { selector: {type: 'any'} };
 
   // Skip if we aren't changing the parent id
   if (oldDoc.parent.id === parentRef.id) return;
 
+  // Get the parent and its ancestry
+  let {parentDoc, parent, ancestors} = getAncestry({parentRef});
+
+  // If the doc and its parent are in the same collection, apply the allowed
+  // parent rules based on type
+  if (docRef.collection === parentRef.collection){
+    let parentAllowed = isParentAllowed({
+      parentType: parentDoc.type,
+      childType: oldDoc.type
+    });
+    if (!parentAllowed){
+      throw new Meteor.Error('invalid parenting',
+        `Can't make ${oldDoc.type} a child of ${parentDoc.type}`)
+    }
+  }
+
   // update the document's parenting
-  let {parent, ancestors} = getAncestry({parentRef});
   collection.update(docRef.id, {
     $set: {parent, ancestors}
   }, updateOptions);