Add m.presence event.

src/presence.rs

@@ -1 +1,45 @@
 //! Events within the *m.presence* namespace.
+
+use core::Event;
+
+/// Informs the client of a user's presence state change.
+pub struct Presence<'a> {
+    content: PresenceContent<'a>,
+    event_id: &'a str,
+}
+
+impl<'a> Event<'a, PresenceContent<'a>> for Presence<'a> {
+    fn content(&'a self) -> &'a PresenceContent {
+        &self.content
+    }
+
+    fn event_type(&self) -> &'static str {
+        "m.presence"
+    }
+}
+
+/// The payload of a `Presence` event.
+pub struct PresenceContent<'a> {
+    /// The current avatar URL for this user.
+    avatar_url: Option<&'a str>,
+    /// The current display name for this user.
+    displayname: Option<&'a str>,
+    /// The last time since this used performed some action, in milliseconds.
+    last_active_ago: Option<u64>,
+    /// The presence state for this user.
+    presence: PresenceState,
+}
+
+/// A description of a user's connectivity and availability for chat.
+pub enum PresenceState {
+    /// Connected to the service and available for chat.
+    FreeForChat,
+    /// Connected to the service but not visible to other users.
+    Hidden,
+    /// Disconnected from the service.
+    Offline,
+    /// Connected to the service.
+    Online,
+    /// Connected to the service but not available for chat.
+    Unavailable,
+}