📖 Assignment: Library Management API with Express, TypeScript & MongoDB

🎯 Objective

Develop a Library Management System using Express, TypeScript, and MongoDB (via Mongoose).

Your project must include:

• Proper schema validation
• Business logic enforcement (e.g., availability control on borrow)
• Use of aggregation pipeline
• At least one Mongoose static or instance method
• Use of Mongoose middleware (pre, post)
• Filtering features

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🔧 Core Requirements

• Use Express and TypeScript
• Connect to MongoDB using Mongoose
• Follow the exact API endpoints and response structures described below

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Book Model Fields & Validation

• title (string) — Mandatory. The book’s title.
• author (string) — Mandatory. The book’s author.
• genre (string) — Mandatory. Must be one of: FICTION, NON_FICTION, SCIENCE, HISTORY, BIOGRAPHY, FANTASY.
• isbn (string) — Mandatory and unique. The book’s International Standard Book Number.
• description (string) — Optional. A brief summary or description of the book.
• copies (number) — Mandatory. Non-negative integer representing total copies available.
• available (boolean) — Defaults to true. Indicates if the book is currently available for borrowing.

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Borrow Model Fields & Validation

• book (objectId) — Mandatory. References the borrowed book’s ID.
• quantity (number) — Mandatory. Positive integer representing the number of copies borrowed.
• dueDate (date) — Mandatory. The date by which the book must be returned.

---

Generic Error Response

1. message: A brief error message explaining what went wrong.
2. success: Set to false for error responses.
3. error: The error message or error object returned by the application

{
  "message": "Validation failed",
  "success": false,
  "error": {
    "name": "ValidationError",
    "errors": {
      "copies": {
        "message": "Copies must be a positive number",
        "name": "ValidatorError",
        "properties": {
          "message": "Copies must be a positive number",
          "type": "min",
          "min": 0
        },
        "kind": "min",
        "path": "copies",
        "value": -5
      }
    }
  }
}

---

✨ Main Section (50 Marks)

1. Create Book

POST /api/books

Request:

{
  "title": "The Theory of Everything",
  "author": "Stephen Hawking",
  "genre": "SCIENCE",
  "isbn": "9780553380163",
  "description": "An overview of cosmology and black holes.",
  "copies": 5,
  "available": true
}

Response:

{
  "success": true,
  "message": "Book created successfully",
  "data": {
    "_id": "64f123abc4567890def12345",
    "title": "The Theory of Everything",
    "author": "Stephen Hawking",
    "genre": "SCIENCE",
    "isbn": "9780553380163",
    "description": "An overview of cosmology and black holes.",
    "copies": 5,
    "available": true,
    "createdAt": "2024-11-19T10:23:45.123Z",
    "updatedAt": "2024-11-19T10:23:45.123Z"
  }
}

---

2. Get All Books

GET /api/books

Supports filtering, and sorting.

Example Query:

/api/books?filter=FANTASY&sortBy=createdAt&sort=desc&limit=5

Query Parameters:

• filter: Filter by genre
• sort: asc or desc
• limit: Number of results (default: 10)

Response:

{
  "success": true,
  "message": "Books retrieved successfully",
  "data": [
    {
      "_id": "64f123abc4567890def12345",
      "title": "The Theory of Everything",
      "author": "Stephen Hawking",
      "genre": "SCIENCE",
      "isbn": "9780553380163",
      "description": "An overview of cosmology and black holes.",
      "copies": 5,
      "available": true,
      "createdAt": "2024-11-19T10:23:45.123Z",
      "updatedAt": "2024-11-19T10:23:45.123Z"
    }
    {...}
  ]
}

---

3. Get Book by ID

GET /api/books/:bookId

Response:

{
  "success": true,
  "message": "Book retrieved successfully",
  "data": {
    "_id": "64f123abc4567890def12345",
    "title": "The Theory of Everything",
    "author": "Stephen Hawking",
    "genre": "SCIENCE",
    "isbn": "9780553380163",
    "description": "An overview of cosmology and black holes.",
    "copies": 5,
    "available": true,
    "createdAt": "2024-11-19T10:23:45.123Z",
    "updatedAt": "2024-11-19T10:23:45.123Z"
  }
}

---

4. Update Book

PUT /api/books/:bookId

Request:

{
  "copies": 50
}

Response:

{
  "success": true,
  "message": "Book updated successfully",
  "data": {
    "_id": "64f123abc4567890def12345",
    "title": "The Theory of Everything",
    "author": "Stephen Hawking",
    "genre": "SCIENCE",
    "isbn": "9780553380163",
    "description": "An overview of cosmology and black holes.",
    "copies": 50,
    "available": true,
    "createdAt": "2024-11-19T10:23:45.123Z",
    "updatedAt": "2024-11-20T08:30:00.000Z"
  }
}

---

5. Delete Book

DELETE /api/books/:bookId

Response:

{
  "success": true,
  "message": "Book deleted successfully",
  "data": null
}

---

6. Borrow a Book

POST /api/borrow

Business Logic:

• Verify the book has enough available copies.
• Deduct the requested quantity from the book’s copies.
• If copies become 0, update available to false (implement this using a static method or instance method).
• Save the borrow record with all relevant details.

Request:

{
  "book": "64ab3f9e2a4b5c6d7e8f9012",
  "quantity": 2,
  "dueDate": "2025-07-18T00:00:00.000Z"
}

Response:

{
  "success": true,
  "message": "Book borrowed successfully",
  "data": {
    "_id": "64bc4a0f9e1c2d3f4b5a6789",
    "book": "64ab3f9e2a4b5c6d7e8f9012",
    "quantity": 2,
    "dueDate": "2025-07-18T00:00:00.000Z",
    "createdAt": "2025-06-18T07:12:15.123Z",
    "updatedAt": "2025-06-18T07:12:15.123Z"
  }
}

---

7. Borrowed Books Summary (Using Aggregation)

GET /api/borrow

Purpose:

Return a summary of borrowed books, including:

• Total borrowed quantity per book (totalQuantity)
• Book details: title and isbn

Details:

Use MongoDB aggregation pipeline to:

• Group borrow records by book
• Sum total quantity borrowed per book
• Return book info and total borrowed quantity

Response:

{
  "success": true,
  "message": "Borrowed books summary retrieved successfully",
  "data": [
    {
      "book": {
        "title": "The Theory of Everything",
        "isbn": "9780553380163"
      },
      "totalQuantity": 5
    },
    {
      "book": {
        "title": "1984",
        "isbn": "9780451524935"
      },
      "totalQuantity": 3
    }
  ]
}

💡 Pro Tip: Strictly follow the exact API endpoints and response formats provided in this document — any deviation may result in mark deduction.

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✨ Bonus Section (10 Marks)

• Code Quality: Clean, readable code with meaningful names.
• API Structure: Follow provided endpoints and response formats exactly.
• Error Handling: Handle invalid input, 404s, and validation errors clearly.
• Video Explanation: Short recorded video explaining key features and logic.
• Documentation: Well-written README.md with setup and API details.

Submission:

1. GitHub Repository Link
2. Live Deployment Link
3. Video Explanation (Public Link)
4. Professional README file with features of your application and instructions on setting up the project locally.

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Deadline:

• 60 Marks: Jun 21, 2025 - 11:59 PM
• 50 Marks: Jun 22, 2025 - 11:59 PM
• 30 Marks: After Jun 22, 2025

🚫 Important Note:

Plagiarism will not be tolerated. Ensure that the code you submit is your work. Any instances of plagiarism will result in 0 Marks.

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By following these instructions, you'll be well-equipped to complete Assignment 3 successfully. Good luck! 🍀