First pass on reorganizing the backend.

This is primarily renames and repackagings.

1 files changed, 85 insertions, 0 deletions

diff --git a/src/event/extract.rs b/src/event/extract.rs
new file mode 100644
index 0000000..e3021e2
--- /dev/null
+++ b/src/event/extract.rs
@@ -0,0 +1,85 @@
+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
+    }
+}