Support for Aggregate Queries (#4207)

* Support for Aggregate Queries

* improve pg and coverage

* Mongo 3.4 aggregates and tests

* replace _id with objectId

* improve tests for objectId

* project with group query

* typo

src/Routers/AggregateRouter.js

@@ -0,0 +1,77 @@
+import ClassesRouter from './ClassesRouter';
+import rest from '../rest';
+import * as middleware from '../middlewares';
+import Parse         from 'parse/node';
+
+const ALLOWED_KEYS = [
+  'where',
+  'distinct',
+  'project',
+  'match',
+  'redact',
+  'limit',
+  'skip',
+  'unwind',
+  'group',
+  'sample',
+  'sort',
+  'geoNear',
+  'lookup',
+  'out',
+  'indexStats',
+  'facet',
+  'bucket',
+  'bucketAuto',
+  'sortByCount',
+  'addFields',
+  'replaceRoot',
+  'count',
+  'graphLookup',
+];
+
+export class AggregateRouter extends ClassesRouter {
+
+  handleFind(req) {
+    const body = Object.assign(req.body, ClassesRouter.JSONFromQuery(req.query));
+    const options = {};
+    const pipeline = [];
+
+    for (const key in body) {
+      if (ALLOWED_KEYS.indexOf(key) === -1) {
+        throw new Parse.Error(Parse.Error.INVALID_QUERY, `Invalid parameter for query: ${key}`);
+      }
+      if (key === 'group') {
+        if (body[key].hasOwnProperty('_id')) {
+          throw new Parse.Error(
+            Parse.Error.INVALID_QUERY,
+            `Invalid parameter for query: group. Please use objectId instead of _id`
+          );
+        }
+        if (!body[key].hasOwnProperty('objectId')) {
+          throw new Parse.Error(
+            Parse.Error.INVALID_QUERY,
+            `Invalid parameter for query: group. objectId is required`
+          );
+        }
+        body[key]._id = body[key].objectId;
+        delete body[key].objectId;
+      }
+      pipeline.push({ [`$${key}`]: body[key] });
+    }
+    if (body.distinct) {
+      options.distinct = String(body.distinct);
+    }
+    options.pipeline = pipeline;
+    if (typeof body.where === 'string') {
+      body.where = JSON.parse(body.where);
+    }
+    return rest.find(req.config, req.auth, this.className(req), body.where, options, req.info.clientSDK)
+      .then((response) => { return { response }; });
+  }
+
+  mountRoutes() {
+    this.route('GET','/aggregate/:className', middleware.promiseEnforceMasterKeyAccess, req => { return this.handleFind(req); });
+  }
+}
+
+export default AggregateRouter;