identity-service-api: Add /versions endpoint (MSC2320)

crates/ruma-identity-service-api/src/discovery.rs

@@ -0,0 +1,4 @@
+//! Various endpoints related to identity server status and metadata discovery.
+
+pub mod get_server_status;
+pub mod get_supported_versions;

crates/ruma-identity-service-api/src/discovery/get_supported_versions.rs

@@ -0,0 +1,68 @@
+//! `GET /_matrix/identity/versions` ([spec])
+//!
+//! [spec]: https://spec.matrix.org/v1.2/identity-service-api/#get_matrixidentityversions
+//!
+//! Note: This endpoint was only implemented in/after 1.1, so a 404 could indicate the server only
+//! supports 1.0 endpoints. Please use [`server_status`](crate::discovery::server_status) to
+//! double-check.
+//!
+//! Note: This endpoint does not contain an unstable variant for 1.0.
+
+use std::collections::BTreeMap;
+
+use ruma_common::api::{ruma_api, MatrixVersion};
+
+ruma_api! {
+    metadata: {
+        description: "Get the versions of the identity service API supported by this endpoint.",
+        method: GET,
+        name: "versions",
+        stable_path: "/_matrix/identity/versions",
+        rate_limited: false,
+        authentication: None,
+        added: 1.1,
+    }
+
+    #[derive(Default)]
+    request: {}
+
+    response: {
+        /// A list of Matrix client API protocol versions supported by the endpoint.
+        pub versions: Vec<String>,
+    }
+}
+
+impl Request {
+    /// Creates an empty `Request`.
+    pub fn new() -> Self {
+        Self {}
+    }
+}
+
+impl Response {
+    /// Creates a new `Response` with the given `versions`.
+    pub fn new(versions: Vec<String>) -> Self {
+        Self { versions }
+    }
+
+    /// Extracts known Matrix versions from this response.
+    ///
+    /// Matrix versions that Ruma cannot parse, or does not know about, are discarded.
+    ///
+    /// The versions returned will be sorted from oldest to latest. Use [`.find()`][Iterator::find]
+    /// or [`.rfind()`][DoubleEndedIterator::rfind] to look for a minimum or maximum version to use
+    /// given some constraint.
+    pub fn known_versions(&self) -> impl Iterator<Item = MatrixVersion> + DoubleEndedIterator {
+        self.versions
+            .iter()
+            // Parse, discard unknown versions
+            .flat_map(|s| s.parse::<MatrixVersion>())
+            // Map to key-value pairs where the key is the major-minor representation
+            // (which can be used as a BTreeMap unlike MatrixVersion itself)
+            .map(|v| (v.into_parts(), v))
+            // Collect to BTreeMap
+            .collect::<BTreeMap<_, _>>()
+            // Return an iterator over just the values (`MatrixVersion`s)
+            .into_values()
+    }
+}

crates/ruma-identity-service-api/src/lib.rs

@@ -11,10 +11,10 @@ use std::fmt;
 
 pub mod association;
 pub mod authentication;
+pub mod discovery;
 pub mod invitation;
 pub mod keys;
 pub mod lookup;
-pub mod status;
 pub mod tos;
 
 // Wrapper around `Box<str>` that cannot be used in a meaningful way outside of