From c0a2004ea89034e4b99a2e481bc2558b738a6709 Mon Sep 17 00:00:00 2001
From: Florian Hartwich <hardi@noarch.de>
Date: Tue, 10 Oct 2017 19:03:52 +0200
Subject: [PATCH] add limit offset middleware for users

---
 api/middleware/filter-handler-mongo.js        |  2 +-
 .../limitoffset-middleware-mongo.js           | 70 +++++++++++++++++++
 api/routes/users.js                           |  5 +-
 package.json                                  |  3 +-
 4 files changed, 76 insertions(+), 4 deletions(-)
 create mode 100644 api/middleware/limitoffset-middleware-mongo.js

diff --git a/api/middleware/filter-handler-mongo.js b/api/middleware/filter-handler-mongo.js
index 5dd9ad0..9ae5878 100644
--- a/api/middleware/filter-handler-mongo.js
+++ b/api/middleware/filter-handler-mongo.js
@@ -22,7 +22,7 @@
 "use strict";
 
 const express = require('express');
-const logger = require('debug')('me2:filterware');
+const logger = require('debug')('middleware:filterware');
 
 /**
  * private helper function to filter Objects by given keys
diff --git a/api/middleware/limitoffset-middleware-mongo.js b/api/middleware/limitoffset-middleware-mongo.js
new file mode 100644
index 0000000..12eab7e
--- /dev/null
+++ b/api/middleware/limitoffset-middleware-mongo.js
@@ -0,0 +1,70 @@
+/** This module defines a express.Router() instance
+ * - supporting offset=<number> and limit=<number>*
+ * - calls next with error if a impossible offset and/or limit value is given
+ *
+ *  Note: it expects to be called BEFORE any data fetched from DB
+ *  Note: it sets an object { limit: 0, skip: 0 } with the proper number values in req.locals.limitskip
+ *  Note: it sets an Error-Object to next with error.status set to HTTP status code 400
+ *
+ * @author Johannes Konert
+ * @licence CC BY-SA 4.0
+ *
+ * @module restapi/limitoffset-middleware-mongo
+ * @type {Router}
+ */
+
+// remember: in modules you have 3 variables given by CommonJS
+// 1.) require() function
+// 2.) module.exports
+// 3.) exports (which is module.exports)
+"use strict";
+
+const router = require('express').Router();
+const logger = require('debug')('middleware:offsetlimit');
+
+
+// the exported router with handler
+router.use((req, res, next) => {
+  let offset = undefined;
+  let limit = undefined;
+  const offsetString = req.query.offset;
+  const limitString = req.query.limit;
+  let err = null;
+
+
+  if (offsetString) {
+    console.log(offsetString)
+    if (!isNaN(offsetString)) {
+      offset = parseInt(offsetString);
+      if (offset < 0) {
+        err = new Error('offset is negative')
+      }
+    }
+    else {
+      err = new Error('given offset is not a valid number ' + offsetString);
+    }
+  }
+  if (limitString) {
+    if (!isNaN(limitString)) {
+      limit = parseInt(limitString);
+      if (limit < 1) {
+        err = new Error('limit is zero or negative')
+      }
+    }
+    else {
+      err = new Error('given limit is not a valid number ' + limitString);
+    }
+  }
+  if (err) {
+    logger('problem occurred with limit/offset values');
+    err.status = 400;
+    next(err)
+  } else {
+    res.locals.limitskip = {}; // mongoDB uses parameter object for skip/limit
+    if (limit) res.locals.limitskip.limit = limit;
+    if (offset) res.locals.limitskip.skip = offset;
+    next()
+  }
+});
+
+module.exports = router;
diff --git a/api/routes/users.js b/api/routes/users.js
index 948b879..23feea4 100644
--- a/api/routes/users.js
+++ b/api/routes/users.js
@@ -11,6 +11,7 @@ const codes = require('./http-codes');
 const apiAuthenticationMiddleware = require('../middleware/auth-middleware');
 const checkHl = require('../middleware/permission-check').checkHl;
 const sortCollectionBy = require('../middleware/util').sortCollection;
+const offsetlimitMiddleware = require('../middleware/limitoffset-middleware-mongo');
 const routerHandling = require('../middleware/router-handling');
 
 // Mongoose Model using mongoDB
@@ -23,6 +24,8 @@ const resultSet = {'__v': 0, 'updatedAt': 0, 'timestamp': 0};
 
 const users = express.Router();
 
+users.get('/', offsetlimitMiddleware);
+
 // routes **********************
 users.route('/')
   .get((req, res, next) => {
@@ -44,7 +47,7 @@ users.route('/')
       const fractionFilter = req.query.fractFilter;
       const squadFilter = req.query.squadId;
 
-      UserModel.find({}, (err, users) => {
+      UserModel.find({}, res.locals.filter, res.locals.limitskip, (err, users) => {
         if (err) return next(err);
         if (users.length === 0) {
           res.locals.items = users;
diff --git a/package.json b/package.json
index 3976222..755ff8b 100644
--- a/package.json
+++ b/package.json
@@ -15,8 +15,7 @@
     "start-e2e": "npm run deploy-static && npm run e2e --prefix ./api",
     "test-e2e": "npm run e2e --prefix ./static"
   },
-  "dependencies": {
-  },
+  "dependencies": {},
   "devDependencies": {
     "concurrently": "^3.4.0",
     "wait-on": "^2.0.2"