REST APIs

npm init
make sure you use module  instead of commonjs
"type": "module",
npm i express nodemon
insert start script in package.json  "server": "nodemon app.js"
run with 'npm run server' stop with 'ctrl + c'

const express = require("express");

import express from "express";
const app = express();
app.use(express.json());
app.listen(3000, () => {
});

const books = [
  { id: 1, title: "Dune", author: "Herbert", year: 1965 },
  { id: 2, title: "1984", author: "Orwell", year: 1949 },
];
export default app;// at the bottom 

test with http://localhost:3000/
app.get("/", (req, res) => {
  res.json({ message: "success" });
});

test with http://localhost:3000/books/2
app.get("/books/:id", (req, res) => {
  const id = parseInt(req.params.id);
  const book = books.find((b) => b.id === id);
  if (!book) return res.status(404).json({ detail: "book not found" });
  res.json(book);
});

test with http://localhost:3000/books?id=2 
or http://localhost:3000/books 
app.get("/books", (req, res) => {
  const id = req.query.id ? parseInt(req.query.id) : null;
  if (id === null) return res.json(books);
  res.json(books.find((b) => b.id === id));
});

app.post("/books", (req, res) => {
  const book = req.body;
  books.push(book);
  res.json(book);
});

app.use((req, res, next) => {
  console.log(req.method);
  next();
});

if new `uv init[projectName]` then cd into it `code.`
        
`uv add fastapi`
`uv add uvicorn`
Auto-generated interactive docs are served at `/docs` once the app is running
# Run:  uvicorn main:app --reload (serves on http://localhost:8000)
# stop the uvicorn server : ctrl + c
from fastapi import FastAPI, HTTPException

app = FastAPI()

# Using a local list instead of a database for the demo:
books = [
    {"id": 1, "title": "Dune", "author": "Herbert", "year": 1965},
    {"id": 2, "title": "1984", "author": "Orwell", "year": 1949},
]

test with http://localhost:8000/
@app.get("/")
def handler():
    return {"message": "success"}

# The magic of FastAPI: path params, query params, and JSON bodies ALL arrive
# as plain arguments to the handler. Just type-annotate them
# test with http://localhost:8000/books/2
@app.get("/books/{id}")
def get_book(id: int):  # `id: int` -> FastAPI parses/validates it
    for book in books:
        if book["id"] == id:
            return book
    raise HTTPException(status_code=404, detail="book not found")

test with http://localhost:8000/books?id=2 
test with http://localhost:8000/books 
@app.get("/books")
def list_books(id: int | None = None):
    if id is None:
        return books
    return next((b for b in books if b["id"] == id), None)

@app.post("/books")
def create_book(book: dict):
    books.append(book)
    return book

@app.middleware("http")
async def log_requests(request, call_next):
    print(request.method)
    response = await call_next(request)    # call_next is async -> always await it
    return response