serve well-known client and server config

This way users can have a simpler time configuring this stuff and we can
worry about the spec compliance parts and specifying the same thing over
and over parts.

src/api/well_known.rs

@@ -0,0 +1,58 @@
+#![warn(missing_docs, clippy::missing_docs_in_private_items)]
+
+//! Handle requests for `/.well-known/matrix/...` files
+
+use http::StatusCode;
+use ruma::api::{
+    client::discovery::discover_homeserver as client,
+    federation::discovery::discover_homeserver as server,
+};
+
+use crate::{services, Ar, Ra};
+
+/// Handler for `/.well-known/matrix/server`
+pub(crate) async fn server(
+    _: Ar<server::Request>,
+) -> Result<Ra<server::Response>, StatusCode> {
+    let Some(authority) =
+        services().globals.config.server_discovery.server.authority.clone()
+    else {
+        return Err(StatusCode::NOT_FOUND);
+    };
+
+    if authority == services().globals.config.server_name {
+        // Delegation isn't needed in this case
+        return Err(StatusCode::NOT_FOUND);
+    }
+
+    Ok(Ra(server::Response::new(authority)))
+}
+
+/// Handler for `/.well-known/matrix/client`
+pub(crate) async fn client(_: Ar<client::Request>) -> Ra<client::Response> {
+    let authority = services()
+        .globals
+        .config
+        .server_discovery
+        .client
+        .authority
+        .clone()
+        .unwrap_or_else(|| services().globals.config.server_name.clone());
+
+    let scheme = if services().globals.config.server_discovery.client.insecure {
+        "http"
+    } else {
+        "https"
+    };
+
+    let base_url = format!("{scheme}://{authority}");
+
+    // I wish ruma used an actual URL type instead of `String`
+    Ra(client::Response {
+        homeserver: client::HomeserverInfo::new(base_url.clone()),
+        identity_server: None,
+        sliding_sync_proxy: Some(client::SlidingSyncProxyInfo {
+            url: base_url,
+        }),
+    })
+}