Product API

This repository is a simple Node.js/Express application that provides a RESTful API for managing products stored in a MongoDB database. It demonstrates the use of modern JavaScript features (ES modules), mongoose for data modeling, and basic pagination and CRUD operations.

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🗂️ Project Structure

index.js                    # Application entry point
config/db.js                # MongoDB connection helper
controllers/
  product.controller.js     # Route handlers for products
models/
  product.model.js          # Mongoose schema for products
routes/
  product.routes.js         # Express router defining API endpoints

• index.js: bootstraps the server, loads environment variables, applies middleware (CORS and JSON body parsing), and registers the /products router.
• config/db.js: connects to the database using the MONGO_URI from environment.
• product.model.js: defines Product with embedded variants and reviews sub‑documents, plus virtuals and indexes for performance.
• product.controller.js: contains all business logic for listing, creating, updating, deleting products, adding reviews, and updating stock.
• product.routes.js: wires controller functions to REST endpoints.

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🚀 Getting Started

1. Install dependencies:

   pnpm install

2. Create a .env file in the root with:

   PORT=3000
   MONGO_URI=mongodb://localhost:27017/mydb

3. Run the server:

   pnpm start
   # or: node index.js

4. The API will be available at http://localhost:3000.

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📡 API Endpoints

Method	Path	Description
GET	/products	List products (paginated)
POST	/products	Create a new product
GET	/products/:id	Retrieve a single product by ID
PUT	/products/:id	Update a product
DELETE	/products/:id	Delete a product
POST	/products/:id/reviews	Add a review to a product
PATCH	/products/:id/stock	Update stock for a specific SKU

Request Body Notes

• POST /products and PUT /products/:id can include name, category, variants, and reviews.
• POST /products/:id/reviews expects a single review object in request body: { "userId": "<ObjectId>", "rating": 1-5, "comment": "optional" }.
• PATCH /products/:id/stock expects: { "sku": "<variant_sku>", "delta": <number> }.

Pagination

GET /products supports page and limit query parameters. The response includes a pagination object with totals and current page info.

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🛠️ Technologies Used

• Node.js (ES modules)
• Express.js
• MongoDB & Mongoose
• CORS & dotenv

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✅ Additional Notes

• product.model.js defines a virtual property avgRating calculated from embedded reviews.
• Indexes on { category, name } and on variants.sku (unique, sparse) help with query performance and SKU uniqueness.
• Error handling in controllers returns appropriate HTTP status codes and messages.

Feel free to extend the codebase with authentication, validation, or a front‑end client!

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🧠 Detailed Code Overview

config/db.js

This async helper reads MONGO_URI from the environment and uses mongoose.connect() to establish the connection. In case the variable is missing or the connection fails, it logs an error but does not terminate the process. Successful connection is confirmed by a console message.

models/product.model.js

• Variant Schema: Embedded subdocument without its own _id, containing SKU, color, price, and stock. Stock is non-negative and defaults to 0.
• Review Schema: Also embedded and _id-less; stores a reference to the user (userId), a rating between 1 and 5, and an optional comment. Timestamps are enabled so each review has createdAt/updatedAt.
• Product Schema: Top-level document with name, category, and arrays of variants and reviews. Timestamps are on the product level as well.
• Virtuals: avgRating computes the average review score at read time and is included when converting documents to JSON/Object.
• Indexes: Compound index on category+name to speed up filtered searches and a sparse unique index on variants.sku to enforce SKU uniqueness only when variants exist.

controllers/product.controller.js

Each exported function corresponds to an API action:

1. getProducts
   • Reads page/limit from query string, applies skip/limit on the Product.find() result sorted by creation date (newest first).
   • Returns both the matching documents and pagination metadata (totalProducts, totalPages, etc.).
2. createProduct
   • Constructs a new Product from req.body and saves it. Responds with 201 Created on success.
3. getProductById
   • Fetches a product by its Mongo _id; 404 if not found.
4. updateProduct
   • Uses findByIdAndUpdate with runValidators so schema rules apply to updates. Returns the updated document.
5. deleteProduct
   • Removes the document and returns confirmation plus the deleted object.
6. addReview
   • Pushes a new review into reviews array using $push; returns the updated product with status 201.
7. updateStock
   • Atomically increments ($inc) the stock field of a specific variant identified by SKU. Handles the case where either product or SKU is missing.

Error handling generally catches exceptions and responds with a 500 or 400 as appropriate, including the error message for debugging.

routes/product.routes.js

Express router maps HTTP methods and paths to controller functions for listing, creating, reading, updating, deleting, review creation, and stock update. All routes use path parameters or JSON body payloads as required.

index.js

Loads environment variables (dotenv), creates the Express app, and configures CORS and JSON parsing middleware. Calls connectDB() before setting up routes to ensure the database is available. Finally, it defines a simple root endpoint and starts listening on the PORT from the environment (default 3000).

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With these details in place, the README now gives readers both high-level context and low-level understanding of how each piece works together.