105 lines
3.4 KiB
JavaScript
105 lines
3.4 KiB
JavaScript
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/** This module defines a express.Router() instance
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* - supporting filter=key1,key2
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* - it sets res.locals.filter to a string "key1 key2"
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* - calls next with error if a filter=key is given, but key does not exist (not raised on empty item arrays!)
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*
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* Note: it expects to be called before any data is fetched from DB
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* Note: it sets an Error-Object to next with error.status set to HTTP status code 400
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*
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* @author Johannes Konert
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* @licence CC BY-SA 4.0
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*
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* @module restapi/filter-middleware-mongo
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* @type {Factory function returning an Router}
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* @param Schema {Object} a MongooseSchema.path value or similar object with attributes representing the valid keys
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* @param suppressId {Boolean} if true, the _id is not returned implicitly
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*/
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// remember: in modules you have 3 variables given by CommonJS
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// 1.) require() function
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// 2.) module.exports
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// 3.) exports (which is module.exports)
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"use strict";
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const express = require('express');
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const logger = require('debug')('me2:filterware');
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/**
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* private helper function to filter Objects by given keys
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* @param keys {Array} the keys from GET parameter filter
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* @param schema [Object} containing the keys as attributes that are allowed
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* @returns {Object or Error} either the filtered items or an Error object
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*/
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const limitFilterToSchema = (keys, schema) => {
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if (!keys || !schema) { // empty arrays evaluate to false
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return undefined; // means no filter at all
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}
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let error = null;
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const result = [];
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// now for each given filter=key1,key2in the array check that the schema allows this key and store it in result
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keys.forEach((key) => {
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if (schema.hasOwnProperty(key)) {
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result.push(key);
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} else {
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error = new Error('given key for filter does not exist in ressource: ' + key);
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}
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});
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return error ? error : result
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};
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/**
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* closure function as factory returning the router
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*
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* @param Schema {Object} a MongooseSchema.path value or similar object with attributes representing the valid keys
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* @param suppressId {Boolean} if true, the _id is not returned implicitly
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* @returns {Router}
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*/
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const createFilterRouter = (schema, supressID) => {
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const router = express.Router();
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// the exported router with handler
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router.use((req, res, next) => {
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const filterString = req.query.filter;
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let filterKeys = [];
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let err = null;
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if (filterString !== undefined) {
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filterKeys = filterString.split(',');
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filterKeys.forEach((item, index, array) => {
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array[index] = item.trim();
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});
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filterKeys = filterKeys.filter((item) => {
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return item.length > 0;
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});
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if (filterKeys.length === 0) {
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err = new Error('given filter does not contain any keys');
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err.status = 400;
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} else {
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const result = limitFilterToSchema(filterKeys, schema);
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if (result instanceof Error) {
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err = result;
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err.status = 400;
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} else {
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res.locals.filter = result.join(' '); // create a string with space as seperator
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if (supressID) {
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res.locals.filter = '-_id ' + res.locals.filter;
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}
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}
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}
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}
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if (err) {
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logger(err);
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next(err)
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} else {
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if (res.locals.filter) {
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logger('Successfully set filter to ' + res.locals.filter);
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}
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next()
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}
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});
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return router;
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};
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module.exports = createFilterRouter;
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