Improve INVITE: validate target, channel membership, op status

INVITE now returns:
- 401 ERR_NOSUCHNICK if target user doesn't exist
- 442 ERR_NOTONCHANNEL if inviter is not in the channel
- 482 ERR_CHANOPRIVSNEEDED if channel is +i and inviter is not op

The INVITE message delivered to the invitee now uses the full
nickmask prefix (foo!user@host) rather than just the nick, so
clients can match on prefix=StrRe('foo!.*').

1 files changed, 24 insertions, 3 deletions

diff --git a/src/papod.clj b/src/papod.clj
index a9b4e41..2f79aa3 100644
--- a/src/papod.clj
+++ b/src/papod.clj
@@ -3660,12 +3660,32 @@
         (= command "INVITE")
         (let [{:keys [clients channels]} components
               target  (first params)
-              handle  (second params)]
+              handle  (second params)
+              nick    (client-target client)]
           (cond
             (< (count params) 2)
             [(numeric-reply client "461"
                "INVITE :Not enough parameters")]
 
+            (and clients
+                 (not (get @clients target)))
+            [(numeric-reply client "401"
+               (str target " :No such nick/channel"))]
+
+            (and channels handle
+                 (seq (get @channels handle))
+                 (not (contains? (get @channels handle) nick)))
+            [(numeric-reply client "442"
+               (str handle " :You're not on that channel"))]
+
+            (and channels handle
+                 (let [m (chan-modes-for components handle)]
+                   (and (string/includes? m "i")
+                        (not (is-op? components handle nick)))))
+            [(numeric-reply client "482"
+               (str handle
+                    " :You're not channel operator"))]
+
             (and channels handle
                  (contains? (get @channels handle) target))
             [(numeric-reply client "443"
@@ -3673,14 +3693,15 @@
                     " :is already on channel"))]
 
             :else
-            (let [nick (client-target client)]
+            (do
               (when-let [invites (:invites components)]
                 (swap! invites update handle
                        (fnil conj #{}) target))
               (when-let [m (and clients
                                 (get @clients target))]
                 (deliver-to-client! (:w m)
-                  (str ":" nick " INVITE " target
+                  (str ":" (client-prefix client)
+                       " INVITE " target
                        " " handle)))
               [(numeric-reply client "341"
                  (str target " " handle))])))