Guide: Implement an Express.js Alternative to the Atlas Data API

/**
* This file initializes the server, validates API keys for added security,
* and routes requests to the appropriate controller methods.
*/
const rateLimit = require("express-rate-limit");
const express = require("express");
const apiRoutes = require("./routes/api");
const logger = require("./utils/logging");
require("dotenv").config();
const API_KEY = process.env.API_KEY; // Load API key from .env
const API_SECRET = process.env.API_SECRET; // Load API secret from .env
const app = express();
// Middleware for rate limiting
const limiter = rateLimit({
   windowMs: parseInt(process.env.RATE_LIMIT_WINDOW_MS, 10), // 15 minutes
   max: parseInt(process.env.RATE_LIMIT_MAX, 10), // Limit each IP to 100 requests per windowMs
   message: { message: process.env.RATE_LIMIT_MESSAGE },
});
// Apply the rate limiter to all requests
app.use(limiter);
// Middleware for parsing requests
app.use(express.json());
// Middleware for API key authentication and logging
app.use((req, res, next) => {
   logger.info({
      method: req.method,
      url: req.originalUrl,
      body: req.body,
      headers: req.headers,
   });
   const apiKey = req.headers["x-api-key"];
   const apiSecret = req.headers["x-api-secret"];
   if (apiKey === API_KEY && apiSecret === API_SECRET) {
      next(); // Proceed to the next middleware or route
   } else {
      res.status(403).json({ message: "Forbidden: Invalid API Key or Secret" });
   }
});
// Middleware for API routing
app.use("/api", apiRoutes);
// Start the server
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
   console.log(`Server is running on port ${PORT}`);
});

 /**
 * Defines the routes for all API endpoints and maps them to the corresponding functions in the dbController class.
 */
 const express = require('express');
 const dbController = require('../controllers/dbController');
 const router = express.Router();
 router.post('/insertOne', dbController.insertOne);
 router.post('/insertMany', dbController.insertMany);
 router.post('/findOne', dbController.findOne);
 router.post('/find', dbController.find);
 router.post('/updateOne', dbController.updateOne);
 router.post('/deleteOne', dbController.deleteOne);
 router.post('/deleteMany', dbController.deleteMany);
 router.post('/aggregate', dbController.aggregate);
 module.exports = router;

const mongoose = require("mongoose");
require("dotenv").config();
const connections = {}; // Cache for database connections
/**
* Manages MongoDB database connections.
* @param {string} database - The database name.
* @returns {mongoose.Connection} - Mongoose connection instance.
*/
const getDatabaseConnection = (database) => {
   const baseURI = process.env.MONGO_URI;
   const options = process.env.MONGO_OPTIONS || "";
   if (!baseURI) {
      throw new Error("MONGO_URI is not defined in .env file");
   }
   // If connection does not exist, create it
   if (!connections[database]) {
      connections[database] = mongoose.createConnection(
         `${baseURI}/${database}${options}`
      );
      // Handle connection errors
      connections[database].on("error", (err) => {
         console.error(`MongoDB connection error for ${database}:`, err);
      });
      connections[database].once("open", () => {
         console.log(`Connected to MongoDB database: ${database}`);
      });
   }
   return connections[database];
};
module.exports = getDatabaseConnection;

 // Import the mongoose library for MongoDB object modeling
 const mongoose = require("mongoose");
 // Import the function to get a database connection
 const getDatabaseConnection = require("../connection/databaseManager");
 // Initialize an empty object to cache models
 // This helps in reusing models and avoiding redundant model creation
 const modelsCache = {}; // Cache for models (database.collection -> Model)
 /**
 * Creates and retrieves a dynamic model for a given database and collection.
 * This function ensures that the same model is reused if it has already been created.
 *
 * @param {string} database - The name of the database.
 * @param {string} collection - The name of the collection.
 * @returns {mongoose.Model} - The Mongoose model instance for the specified collection.
 */
 const getModel = (database, collection) => {
   // Create a unique key for the model based on the database and collection names
   const modelKey = `${database}.${collection}`;
   // Check if the model already exists in the cache
   // If it does, return the cached model
   if (modelsCache[modelKey]) {
      return modelsCache[modelKey];
   }
   // Get the database connection for the specified database
   const dbConnection = getDatabaseConnection(database);
   // Define a flexible schema with no predefined structure
   // This allows the schema to accept any fields
   const schema = new mongoose.Schema({}, { strict: false });
   // Create the model using the database connection, collection name, and schema
   // Cache the model for future use
   const model = dbConnection.model(collection, schema, collection);
   modelsCache[modelKey] = model;
   // Return the newly created model
   return model;
 };
 // Export the getModel function as a module
 module.exports = getModel;

 /**
 * Contains the logic for all CRUD and aggregation operations.
 * Each method interacts with the database and handles errors gracefully.
 */
 const getModel = require("../models/dynamicModel");
 class DbController {
   async insertOne(req, res) {
      const { database, collection, document } = req.body;
      try {
         const Model = getModel(database, collection);
         const result = await Model.insertOne(document);
         if (!result) {
            return res
            .status(400)
            .json({ success: false, message: "Insertion failed" });
         }
         res.status(201).json({ success: true, result });
      } catch (error) {
         res.status(500).json({ success: false, error: error.message });
      }
   }
   async insertMany(req, res) {
      const { database, collection, documents } = req.body;
      try {
         const Model = getModel(database, collection);
         const result = await Model.insertMany(documents);
         if (!result || result.length === 0) {
            return res
            .status(400)
            .json({ success: false, message: "Insertion failed" });
         }
         res.status(201).json({ success: true, result });
      } catch (error) {
         res.status(500).json({ success: false, error: error.message });
      }
   }
   async findOne(req, res) {
      const { database, collection, filter, projection } = req.body;
      try {
         const Model = getModel(database, collection);
         const result = await Model.findOne(filter, projection);
         if (!result) {
            return res
            .status(404)
            .json({ success: false, message: "No record found" });
         }
         res.status(200).json({ success: true, result });
      } catch (error) {
         res.status(500).json({ success: false, error: error.message });
      }
   }
   async find(req, res) {
      const { database, collection, filter, projection, sort, limit } = req.body;
      try {
         const Model = getModel(database, collection);
         const result = await Model.find(filter, projection).sort(sort).limit(limit);
         if (!result || result.length === 0) {
            return res
            .status(404)
            .json({ success: false, message: "No records found" });
         }
         res.status(200).json({ success: true, result });
      } catch (error) {
      r  es.status(500).json({ success: false, error: error.message });
      }
   }
   async updateOne(req, res) {
      const { database, collection, filter, update, upsert } = req.body;
      try {
         const Model = getModel(database, collection);
         const result = await Model.updateOne(filter, update, { upsert });
         if (result.matchedCount === 0) {
            return res
            .status(404)
            .json({ success: false, message: "No records updated" });
         }
         res.status(200).json({ success: true, result });
      } catch (error) {
         res.status(500).json({ success: false, error: error.message });
      }
   }
   async updateMany(req, res) {
      const { database, collection, filter, update } = req.body;
      try {
         const Model = getModel(database, collection);
         const result = await Model.updateMany(filter, update);
         if (result.matchedCount === 0) {
            return res
            .status(404)
            .json({ success: false, message: "No records updated" });
         }
         res.status(200).json({ success: true, result });
      } catch (error) {
         res.status(500).json({ success: false, error: error.message });
      }
   }
   async deleteOne(req, res) {
      const { database, collection, filter } = req.body;
      try {
         const Model = getModel(database, collection);
         const result = await Model.deleteOne(filter);
         if (result.deletedCount === 0) {
            return res
            .status(404)
            .json({ success: false, message: "No records deleted" });
         }
         res.status(200).json({ success: true, result });
      } catch (error) {
         res.status(500).json({ success: false, error: error.message });
      }
   }
   async deleteMany(req, res) {
      const { database, collection, filter } = req.body;
      try {
      const Model = getModel(database, collection);
      const result = await Model.deleteMany(filter);
      if (result.deletedCount === 0) {
            return res
            .status(404).json({ success: false, message: "No records deleted" });
         }
         res.status(200).json({ success: true, result });
      } catch (error) {
         res.status(500).json({ success: false, error: error.message });
      }
   }
   async aggregate(req, res) {
      const { database, collection, pipeline } = req.body;
      try {
         const Model = getModel(database, collection);
         const result = await Model.aggregate(pipeline);
         if (!result || result.length === 0) {
            return res
            .status(404)
            .json({ success: false, message: "No aggregation results found" });
         }
         res.status(200).json({ success: true, result });
      } catch (error) {
         res.status(500).json({ success: false, error: error.message });
      }
   }
 }
 module.exports = new DbController();