axum/examples/versioning/src/main.rs

//! Run with
//!
//! ```not_rust
//! cd examples && cargo run -p example-versioning
//! ```

use axum::{
    async_trait,
    extract::{FromRequestParts, Path},
    http::{request::Parts, StatusCode},
    response::{IntoResponse, Response},
    routing::get,
    RequestPartsExt, Router,
};
use std::{collections::HashMap, net::SocketAddr};
use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};

#[tokio::main]
async fn main() {
    tracing_subscriber::registry()
        .with(tracing_subscriber::EnvFilter::new(
            std::env::var("RUST_LOG").unwrap_or_else(|_| "example_versioning=debug".into()),
        ))
        .with(tracing_subscriber::fmt::layer())
        .init();

    // build our application with some routes
    let app = Router::new().route("/:version/foo", get(handler));

    // run it
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    tracing::debug!("listening on {}", addr);
    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap();
}

async fn handler(version: Version) {
    println!("received request with version {:?}", version);
}

#[derive(Debug)]
enum Version {
    V1,
    V2,
    V3,
}

#[async_trait]
impl<S> FromRequestParts<S> for Version
where
    S: Send + Sync,
{
    type Rejection = Response;

    async fn from_request_parts(parts: &mut Parts, _state: &S) -> Result<Self, Self::Rejection> {
        let params: Path<HashMap<String, String>> =
            parts.extract().await.map_err(IntoResponse::into_response)?;

        let version = params
            .get("version")
            .ok_or_else(|| (StatusCode::NOT_FOUND, "version param missing").into_response())?;

        match version.as_str() {
            "v1" => Ok(Version::V1),
            "v2" => Ok(Version::V2),
            "v3" => Ok(Version::V3),
            _ => Err((StatusCode::NOT_FOUND, "unknown version").into_response()),
        }
    }
}