axum 0.4.8

Web framework that focuses on ergonomics and modularity
Documentation 
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use http::{Request, Uri};
use std::{
    borrow::Cow,
    sync::Arc,
    task::{Context, Poll},
};
use tower_service::Service;

#[derive(Clone)]
pub(super) struct StripPrefix<S> {
    inner: S,
    prefix: Arc<str>,
}

impl<S> StripPrefix<S> {
    pub(super) fn new(inner: S, prefix: &str) -> Self {
        Self {
            inner,
            prefix: prefix.into(),
        }
    }
}

impl<S, B> Service<Request<B>> for StripPrefix<S>
where
    S: Service<Request<B>>,
{
    type Response = S::Response;
    type Error = S::Error;
    type Future = S::Future;

    #[inline]
    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx)
    }

    fn call(&mut self, mut req: Request<B>) -> Self::Future {
        let new_uri = strip_prefix(req.uri(), &self.prefix);
        *req.uri_mut() = new_uri;
        self.inner.call(req)
    }
}

fn strip_prefix(uri: &Uri, prefix: &str) -> Uri {
    let path_and_query = if let Some(path_and_query) = uri.path_and_query() {
        let new_path = if let Some(path) = path_and_query.path().strip_prefix(prefix) {
            path
        } else {
            path_and_query.path()
        };

        let new_path = if new_path.starts_with('/') {
            Cow::Borrowed(new_path)
        } else {
            Cow::Owned(format!("/{}", new_path))
        };

        if let Some(query) = path_and_query.query() {
            Some(
                format!("{}?{}", new_path, query)
                    .parse::<http::uri::PathAndQuery>()
                    .unwrap(),
            )
        } else {
            Some(new_path.parse().unwrap())
        }
    } else {
        None
    };

    let mut parts = http::uri::Parts::default();
    parts.scheme = uri.scheme().cloned();
    parts.authority = uri.authority().cloned();
    parts.path_and_query = path_and_query;

    Uri::from_parts(parts).unwrap()
}