index.js

import express from 'express'

const app = express()
app.use(express.urlencoded())

const PORT = 4000
let PRODUCTS = [
  {
    "id": 1,
    "title": "Product 1",
    "price": "50",
    "discount": "5"
  },
  {
    "id": 2,
    "title": "Product 2",
    "price": "100",
    "discount": "10"
  },
  {
    "id": 3,
    "title": "Product 3",
    "price": "150",
    "discount": "15"
  }
]
let idCounter = 4

app.get('/', (req, res) => {
  res.send('Welcome to our app :)')
})

// // Products
// // 1. READ - GET /products
app.get('/products', (req, res) => {
  res.json({
    status: 'SUCCESS',
    data: PRODUCTS
  })
})

// 2. CREATE - POST /products
app.post('/products', (req, res) => {
  const { title, price, discount } = req.body

  const newProduct = { id: idCounter++, title, price, discount }

  PRODUCTS.push(newProduct)

  res.status(201).json({
    status: 'SUCCESS',
    message: 'Product created'
  })
})

// 3. UPDATE - PATCH /products/:id
app.patch('/products/:id', (req, res) => {
  const { id } = req.params

  const product = PRODUCTS.find(p => p.id == id)
  if(!product) {
    return res.status(404).json({
      status: 'FAILED',
      message: 'Product not found'
    })
  }

  const { title, price, discount } = req.body

  if(title)
    product.title = title
  if(price)
    product.price = price
  if(discount)
    product.discount = discount

  res.json({
    status: 'SUCCESS',
    message: 'Product updated'
  })
})

// 4. DELETE - DELETE /products/:id
app.delete('/products/:id', (req, res) => {
  const { id } = req.params

  const product = PRODUCTS.find(p => p.id == id)
  if(!product) {
    return res.status(404).json({
      status: 'FAILED',
      message: 'Product not found'
    })
  }

  PRODUCTS = PRODUCTS.filter(p => p.id != id)

  res.json({
    status: 'SUCCESS',
    message: 'Product deleted'
  })
})

/* --------------------------- */
// Query Parameters
// app.get('/products', (req, res) => {
//   let products = [...PRODUCTS]

//   const { minDiscount, budget } = req.query
//   if(minDiscount) {
//     products = products.filter(p => p.discount >= Number(minDiscount))
//   }
//   if(budget) {
//     products = products.filter(p => p.price <= Number(budget))
//   }

//   res.json({
//     status: 'SUCCESS',
//     data: products
//   })
// })

/* --------------------------- */
// Route Parameters
// app.get('/products/:id', (req, res) => {
//   const { id } = req.params

//   const product = PRODUCTS.find(p => p.id == id)
//   if(!product) {
//     return res.status(404).json({
//       status: 'FAILED',
//       message: 'Product not found'
//     })
//   }

//   res.json({
//     status: 'SUCCESS',
//     data: product
//   })
// })

/* --------------------------- */
// UPDATE - PUT /products/:id (Complete replacement)
// app.put('/products/:id', (req, res) => {
//   const { id } = req.params

//   const productIndex = PRODUCTS.findIndex(p => p.id == id)
//   if(productIndex == -1) {
//     return res.status(404).json({
//       status: 'FAILED',
//       message: 'Product not found'
//     })
//   }

//   const { title, price, discount } = req.body

//   PRODUCTS[productIndex] = { id, title, price, discount }

//   res.json({
//     status: 'SUCCESS',
//     message: 'Product updated'
//   })
// })

/* --------------------------- */

app.listen(PORT, () => {
  console.log(`Server is running on http://localhost:${PORT}`)
})

/*
  # REST
    - REpresentational State Transfer
    - A set of guidelines/principles for desigining APIs
    - Introduced in 2000
    - Makes APIs consistent and predictable

    - APIs before REST
      - There was no common standard
      - Different developers designed APIs differently
        - Examples:
          - Fetch products from the server
            - GET /getProducts
            - GET /fetchProducts
            - GET /listProducts
          - Create a product
            - POST /addProduct
            - POST /createProduct
            - POST /newProduct
      - Problems:
        - Difficult to understand
        - Different naming conventions
        - No consistency
      
    - REST Principles:
      1. Resource based URLs
        - Resources are represented using nouns
        - Examples:
          - /products
          - /users
          - /orders
        - Sub resources
          - Add / followed by the sub resource
          - Examples
            - /products/10/reviews (Reviews of product with ID=10)
            - /users/5/followers (Followers of user with ID=5)
      2. Use HTTP Method
        - CRUD operations: Create, Read, Update, Delete
        - CRUD mapped to HTTP Methods
            -----------     ----------- 
            HTTP METHOD     CRUD OPERATION
            -----------     ----------- 
            GET             READ
            POST            CREATE
            PATCH/PUT       UPDATE
            DELETE          DELETE
        - Examples of RESTful APIs:
          - 'products' resource
            - (READ) Fetch products from the server
              - GET /products
            - (Create) Create a product
              - POST /products
            - (Update) Update a product
              - PATCH /products/:id
            - (Delete) Delete a product
              - DELETE /products/:id
          - 'users' resource
            - GET /users
            - POST /users
            - PATCH /users/:id
            - DELETE /users/:id
          - 'orders' resource
            - GET /orders
            - POST /orders
            - PATCH /orders/:id
            - DELETE /orders/:id
      3. Stateless
        - Every request is independent
        - Server does not remember previous requests
        
    - Query parameters
      - Used to send optional information
      - URL: /products?query1=value1&query2=value2
      - Access: req.query
      - Commom uses:
        - Searching
        - Filtering
        - Sorting
        - Pagination

    - Route parameters
      - Used to identify a specific resource
      - URL: /products/10
      - Access: req.params
      - Declare: /products/:id (Hence, req.params.id = 10)

    - PATCH vs PUT
      - PATCH: Partial updates
      - PUT: Complete replacement
      - Reference image: https://javacodehouse.com/assets/img/thumb/PUT-vs-PATCH.svg
*/