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use std::ops::Deref;
use axum::{
extract::FromRequestParts,
http::{request::Parts, HeaderName, HeaderValue},
};
use axum_extra::typed_header::TypedHeader;
use serde::{de::DeserializeOwned, Serialize};
// A typed header. When used as a bare extractor, reads from the
// `Last-Event-Id` HTTP header.
pub struct LastEventId<T>(pub T);
static LAST_EVENT_ID: HeaderName = HeaderName::from_static("last-event-id");
impl<T> headers::Header for LastEventId<T>
where
T: Serialize + DeserializeOwned,
{
fn name() -> &'static HeaderName {
&LAST_EVENT_ID
}
fn decode<'i, I>(values: &mut I) -> Result<Self, headers::Error>
where
I: Iterator<Item = &'i HeaderValue>,
{
let value = values.next().ok_or_else(headers::Error::invalid)?;
let value = value.to_str().map_err(|_| headers::Error::invalid())?;
let value = serde_json::from_str(value).map_err(|_| headers::Error::invalid())?;
Ok(Self(value))
}
fn encode<E>(&self, values: &mut E)
where
E: Extend<HeaderValue>,
{
let Self(value) = self;
// Must panic or suppress; the trait provides no other options.
let value = serde_json::to_string(value).expect("value can be encoded as JSON");
let value = HeaderValue::from_str(&value).expect("LastEventId is a valid header value");
values.extend(std::iter::once(value));
}
}
#[async_trait::async_trait]
impl<S, T> FromRequestParts<S> for LastEventId<T>
where
S: Send + Sync,
T: Serialize + DeserializeOwned,
{
type Rejection = <TypedHeader<Self> as FromRequestParts<S>>::Rejection;
async fn from_request_parts(parts: &mut Parts, state: &S) -> Result<Self, Self::Rejection> {
// This is purely for ergonomics: it allows `RequestedAt` to be extracted
// without having to wrap it in `Extension<>`. Callers _can_ still do that,
// but they aren't forced to.
let TypedHeader(requested_at) = TypedHeader::from_request_parts(parts, state).await?;
Ok(requested_at)
}
}
impl<T> Deref for LastEventId<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
let Self(header) = self;
header
}
}
impl<T> From<T> for LastEventId<T> {
fn from(value: T) -> Self {
Self(value)
}
}
impl<T> LastEventId<T> {
pub fn into_inner(self) -> T {
let Self(value) = self;
value
}
}
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