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extern crate log;
extern crate pretty_env_logger;
extern crate serde;
extern crate serde_derive;
extern crate warp;
use std::env;
use std::sync::{Arc, Mutex};
use warp::{http::StatusCode, Filter};
/// So we don't have to tackle how different database work, we'll just use
/// a simple in-memory DB, a vector synchronized by a mutex.
type Db = Arc<Mutex<Vec<Todo>>>;
#[derive(Debug, Deserialize, Serialize)]
struct Todo {
id: u64,
text: String,
completed: bool,
/// Provides a RESTful web server managing some Todos.
/// API will be:
/// - `GET /todos`: return a JSON list of Todos.
/// - `POST /todos`: create a new Todo.
/// - `PUT /todos/:id`: update a specific Todo.
/// - `DELETE /todos/:id`: delete a specific Todo.
fn main() {
if env::var_os("RUST_LOG").is_none() {
// Set `RUST_LOG=todos=debug` to see debug logs,
// this only shows access logs.
env::set_var("RUST_LOG", "todos=info");
// These are some `Filter`s that several of the endpoints share,
// so we'll define them here and reuse them below...
// Turn our "state", our db, into a Filter so we can combine it
// easily with others...
let db = Arc::new(Mutex::new(Vec::<Todo>::new()));
let db = warp::any().map(move || db.clone());
// Just the path segment "todos"...
let todos = warp::path("todos");
// Combined with `end`, this means nothing comes after "todos".
// So, for example: `GET /todos`, but not `GET /todos/32`.
let todos_index = todos.and(warp::path::end());
// Combined with an id path parameter, for refering to a specific Todo.
// For example, `POST /todos/32`, but not `POST /todos/32/something-more`.
let todos_id = todos.and(warp::path::param::<u64>()).and(warp::path::end());
// When accepting a body, we want a JSON body
// (and to reject huge payloads)...
let json_body = warp::body::content_length_limit(1024 * 16).and(warp::body::json());
// Next, we'll define each our 4 endpoints:
// `GET /todos`
let list = warp::get2()
// `POST /todos`
let create = warp::post2()
// `PUT /todos/:id`
let update = warp::put2()
// `DELETE /todos/:id`
let delete = warp::delete2()
// Combine our endpoints, since we want requests to match any of them:
let api = list.or(create).or(update).or(delete);
// View access logs by setting `RUST_LOG=todos`.
let routes = api.with(warp::log("todos"));
// Start up the server...
warp::serve(routes).run(([127, 0, 0, 1], 3030));
// These are our API handlers, the ends of each filter chain.
// Notice how thanks to using `Filter::and`, we can define a function
// with the exact arguments we'd expect from each filter in the chain.
// No tuples are needed, it's auto flattened for the functions.
/// GET /todos
fn list_todos(db: Db) -> impl warp::Reply {
// Just return a JSON array of all Todos.
/// POST /todos with JSON body
fn create_todo(create: Todo, db: Db) -> Result<impl warp::Reply, warp::Rejection> {
debug!("create_todo: {:?}", create);
let mut vec = db.lock().unwrap();
for todo in vec.iter() {
if == {
debug!(" -> id already exists: {}",;
// Todo with id already exists, return `400 BadRequest`.
return Ok(StatusCode::BAD_REQUEST);
// No existing Todo with id, so insert and return `201 Created`.
/// PUT /todos/:id with JSON body
fn update_todo(id: u64, update: Todo, db: Db) -> Result<impl warp::Reply, warp::Rejection> {
debug!("update_todo: id={}, todo={:?}", id, update);
let mut vec = db.lock().unwrap();
// Look for the specified Todo...
for todo in vec.iter_mut() {
if == id {
*todo = update;
return Ok(warp::reply());
debug!(" -> todo id not found!");
// If the for loop didn't return OK, then the ID doesn't exist...
/// DELETE /todos/:id
fn delete_todo(id: u64, db: Db) -> Result<impl warp::Reply, warp::Rejection> {
debug!("delete_todo: id={}", id);
let mut vec = db.lock().unwrap();
let len = vec.len();
vec.retain(|todo| {
// Retain all Todos that aren't this id...
// In other words, remove all that *are* this id... != id
// If the vec is smaller, we found and deleted a Todo!
let deleted = vec.len() != len;
if deleted {
// respond with a `204 No Content`, which means successful,
// yet no body expected...
} else {
debug!(" -> todo id not found!");
// Reject this request with a `404 Not Found`...
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