Implement LUSERS, WHOWAS, INFO, INVITE; fix AWAY, LIST, WHO

New commands:
- LUSERS: return 251-255 with user/channel counts (only counts
  registered clients to avoid stale-state inflation)
- WHOWAS: return 406 (no such nickname) + 369 (end of WHOWAS)
  for all queries (no history tracking yet)
- INFO: return 371 (server info) + 374 (end of INFO)
- INVITE: send invite to target, return 341 (inviting) or
  443 (already on channel)

Fixes:
- AWAY: empty trailing param (AWAY :) now unsets away status
- LIST: only show channels with active members; support
  LIST #specific filtering
- WHO: include away flag (H=here, G=gone) in 352 replies

irctest: 214 passed, 440 failed, 218 skipped (up from 205).
Unit: 260 assertions, Integration: 38 assertions — all pass.

1 files changed, 113 insertions, 28 deletions

diff --git a/src/papod.clj b/src/papod.clj
index f29b3f6..94c7bb2 100644
--- a/src/papod.clj
+++ b/src/papod.clj
@@ -2432,16 +2432,17 @@
 
 (defn- handle-away
   [params client]
-  (if (empty? params)
-    (do (swap! client dissoc :away)
-        [(numeric-reply client "305"
-           ":You are no longer marked as being away")])
-    (let [msg (string/join " " params)
-          msg (cond-> msg
-                (string/starts-with? msg ":") (subs 1))]
-      (swap! client assoc :away msg)
-      [(numeric-reply client "306"
-         ":You have been marked as being away")])))
+  (let [msg (when (seq params)
+              (let [raw (string/join " " params)]
+                (cond-> raw
+                  (string/starts-with? raw ":") (subs 1))))]
+    (if (or (empty? params) (string/blank? msg))
+      (do (swap! client dissoc :away)
+          [(numeric-reply client "305"
+             ":You are no longer marked as being away")])
+      (do (swap! client assoc :away msg)
+          [(numeric-reply client "306"
+             ":You have been marked as being away")]))))
 
 (defn- replies-for!
   [message client components]
@@ -2566,38 +2567,107 @@
                 (for [mn members
                       :let [m (when clients
                                 (get @clients mn))]
-                      :when m]
+                      :when m
+                      :let [ca   (:client-atom m)
+                            away (when ca (:away @ca))
+                            flag (if away "G" "H")
+                            uname (or (some-> ca deref
+                                        :user :username)
+                                      mn)]]
                   (numeric-reply client "352"
-                    (str target " "
-                         (or (some-> (:client-atom m) deref
-                                     :user :username)
-                             mn)
+                    (str target " " uname
                          " localhost " +server-name+
-                         " " mn " H :0 " mn))))
+                         " " mn " " flag " :0 " mn))))
                [(numeric-reply client "315"
                   (str target " :End of /WHO list"))]))
             ;; WHO <nick>
             :else
             (let [m (when clients (get @clients target))]
               (if m
-                [(numeric-reply client "352"
-                   (str "* "
-                        (or (some-> (:client-atom m) deref
-                                     :user :username)
-                            target)
-                        " localhost " +server-name+
-                        " " target " H :0 " target))
-                 (numeric-reply client "315"
-                   (str target " :End of /WHO list"))]
+                (let [ca   (:client-atom m)
+                      away (when ca (:away @ca))
+                      flag (if away "G" "H")
+                      uname (or (some-> ca deref
+                                  :user :username)
+                                target)]
+                  [(numeric-reply client "352"
+                     (str "* " uname
+                          " localhost " +server-name+
+                          " " target " " flag
+                          " :0 " target))
+                   (numeric-reply client "315"
+                     (str target " :End of /WHO list"))])
                 [(numeric-reply client "315"
                    (str target " :End of /WHO list"))]))))
 
         (= command "LUSERS")
-        []
+        (let [{:keys [clients channels]} components
+              n-users (if clients
+                        (count
+                         (filter
+                          (fn [[_ m]]
+                            (some-> (:client-atom m) deref
+                                    :registered?))
+                          @clients))
+                        0)
+              n-chans (if channels (count @channels) 0)]
+          [(numeric-reply client "251"
+             (str ":There are " n-users
+                  " users and 0 invisible on 1 servers"))
+           (numeric-reply client "252"
+             "0 :operator(s) online")
+           (numeric-reply client "253"
+             "0 :unknown connection(s)")
+           (numeric-reply client "254"
+             (str n-chans " :channels formed"))
+           (numeric-reply client "255"
+             (str ":I have " n-users
+                  " clients and 0 servers"))])
 
         (= command "MOTD")
         [(numeric-reply client "422" ":MOTD File is missing")]
 
+        (= command "WHOWAS")
+        (if (empty? params)
+          [(numeric-reply client "431" ":No nickname given")]
+          (let [target (first params)]
+            [(numeric-reply client "406"
+               (str target " :There was no such nickname"))
+             (numeric-reply client "369"
+               (str target " :End of WHOWAS"))]))
+
+        (= command "INFO")
+        [(numeric-reply client "371"
+           (str ":papod " +version+
+                " - IRC server"))
+         (numeric-reply client "374"
+           ":End of /INFO list")]
+
+        (= command "INVITE")
+        (let [{:keys [clients channels]} components
+              target  (first params)
+              handle  (second params)]
+          (cond
+            (< (count params) 2)
+            [(numeric-reply client "461"
+               "INVITE :Not enough parameters")]
+
+            (and channels handle
+                 (contains? (get @channels handle) target))
+            [(numeric-reply client "443"
+               (str target " " handle
+                    " :is already on channel"))]
+
+            :else
+            (let [nick (client-target client)]
+              (when-let [m (and clients
+                                (get @clients target))]
+                (deliver-to-client! (:w m)
+                  (str ":" nick " INVITE " target
+                       " " handle)))
+              [(numeric-reply client "341"
+                 (str target " " handle))])))
+
         ;; Network-scoped commands
         (not (:network-id @client))
         [(numeric-reply client "451"
@@ -2616,8 +2686,23 @@
           "EDIT"        (handle-edit params client components)
           "TAGMSG"      (handle-tagmsg message client components)
           "MARKREAD"    (handle-markread params client components)
-          "LIST"        [(numeric-reply client "323"
-                           ":End of /LIST")]
+          "LIST"        (let [filter-ch (first params)
+                              chans (when (:channels components)
+                                      @(:channels components))
+                              active (filter
+                                      (fn [[ch members]]
+                                        (and (seq members)
+                                             (or (nil? filter-ch)
+                                                 (= ch filter-ch))))
+                                      chans)]
+                          (conj
+                           (vec
+                            (for [[ch members] active]
+                              (numeric-reply client "322"
+                                (str ch " "
+                                     (count members) " :"))))
+                           (numeric-reply client "323"
+                             ":End of /LIST")))
           "NAMES"       (let [handle (first params)]
                           (if (and handle
                                    (:channels components)