Sort the list of memberships

src/data/conversation.rs

@@ -4,7 +4,7 @@
 
 use crate::data::user::UserID;
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq, Eq)]
 pub struct Conversation {
     pub id: u64,
     pub owner_id: UserID,

src/data/friend.rs

@@ -4,6 +4,7 @@
 
 use crate::data::user::UserID;
 
+#[derive(PartialEq, Eq)]
 pub struct Friend {
     pub friend_id: UserID,
     pub accepted: bool,

src/data/user_membership.rs

@@ -2,12 +2,37 @@
 //!
 //! @author Pierre Hubert
 
-use crate::data::friend::Friend;
+use std::cmp::Ordering;
+
 use crate::data::conversation::Conversation;
+use crate::data::friend::Friend;
 use crate::data::group_id::GroupID;
 
+#[derive(PartialEq, Eq)]
 pub enum UserMembership {
     Group(GroupID, u64),
     Friend(Friend),
-    Conversation(Conversation)
+    Conversation(Conversation),
+}
+
+impl UserMembership {
+    pub fn last_active(&self) -> u64 {
+        match self {
+            UserMembership::Group(_, last_active) => *last_active,
+            UserMembership::Friend(f) => f.last_activity_time,
+            UserMembership::Conversation(c) => c.last_active,
+        }
+    }
+}
+
+impl PartialOrd for UserMembership {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        self.last_active().partial_cmp(&other.last_active())
+    }
+}
+
+impl Ord for UserMembership {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.last_active().cmp(&other.last_active())
+    }
 }