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#![deny(warnings)]
use std::convert::Infallible;
use std::error::Error;
use std::num::NonZeroU16;
use serde_derive::{Deserialize, Serialize};
use warp::http::StatusCode;
use warp::{reject, Filter, Rejection, Reply};
/// Rejections represent cases where a filter should not continue processing
/// the request, but a different filter *could* process it.
#[tokio::main]
async fn main() {
let math = warp::path!("math" / u16);
let div_with_header = math
.and(warp::get())
.and(div_by())
.map(|num: u16, denom: NonZeroU16| {
warp::reply::json(&Math {
op: format!("{} / {}", num, denom),
output: num / denom.get(),
})
});
let div_with_body =
math.and(warp::post())
.and(warp::body::json())
.map(|num: u16, body: DenomRequest| {
warp::reply::json(&Math {
op: format!("{} / {}", num, body.denom),
output: num / body.denom.get(),
})
});
let routes = div_with_header.or(div_with_body).recover(handle_rejection);
warp::serve(routes).run(([127, 0, 0, 1], 3030)).await;
}
/// Extract a denominator from a "div-by" header, or reject with DivideByZero.
fn div_by() -> impl Filter<Extract = (NonZeroU16,), Error = Rejection> + Copy {
warp::header::<u16>("div-by").and_then(|n: u16| async move {
if let Some(denom) = NonZeroU16::new(n) {
Ok(denom)
} else {
Err(reject::custom(DivideByZero))
}
})
}
#[derive(Deserialize)]
struct DenomRequest {
pub denom: NonZeroU16,
}
#[derive(Debug)]
struct DivideByZero;
impl reject::Reject for DivideByZero {}
// JSON replies
/// A successful math operation.
#[derive(Serialize)]
struct Math {
op: String,
output: u16,
}
/// An API error serializable to JSON.
#[derive(Serialize)]
struct ErrorMessage {
code: u16,
message: String,
}
// This function receives a `Rejection` and tries to return a custom
// value, otherwise simply passes the rejection along.
async fn handle_rejection(err: Rejection) -> Result<impl Reply, Infallible> {
let code;
let message;
if err.is_not_found() {
code = StatusCode::NOT_FOUND;
message = "NOT_FOUND";
} else if let Some(DivideByZero) = err.find() {
code = StatusCode::BAD_REQUEST;
message = "DIVIDE_BY_ZERO";
} else if let Some(e) = err.find::<warp::filters::body::BodyDeserializeError>() {
// This error happens if the body could not be deserialized correctly
// We can use the cause to analyze the error and customize the error message
message = match e.source() {
Some(cause) => {
if cause.to_string().contains("denom") {
"FIELD_ERROR: denom"
} else {
"BAD_REQUEST"
}
}
None => "BAD_REQUEST",
};
code = StatusCode::BAD_REQUEST;
} else if let Some(_) = err.find::<warp::reject::MethodNotAllowed>() {
// We can handle a specific error, here METHOD_NOT_ALLOWED,
// and render it however we want
code = StatusCode::METHOD_NOT_ALLOWED;
message = "METHOD_NOT_ALLOWED";
} else {
// We should have expected this... Just log and say its a 500
eprintln!("unhandled rejection: {:?}", err);
code = StatusCode::INTERNAL_SERVER_ERROR;
message = "UNHANDLED_REJECTION";
}
let json = warp::reply::json(&ErrorMessage {
code: code.as_u16(),
message: message.into(),
});
Ok(warp::reply::with_status(json, code))
}