Implement draft/metadata-2 before-connect optional behavior

Clients with draft/metadata-2 + batch can now METADATA * SET/GET/LIST/
CLEAR before completing registration. Pre-registration values are
buffered on the client atom and replayed in a metadata BATCH at the
end of the welcome burst, then merged into the global metadata atom
under the registered nick.

The value-suffix form ("draft/metadata-2=before-connect") is only sent
in CAP LS 302 replies; CAP LS without a 302 version still emits the
bare name to avoid IRCv3.1 clients seeing name=value capabilities.

1 files changed, 112 insertions, 4 deletions

diff --git a/src/papod.clj b/src/papod.clj
index d96bb87..e20bec8 100644
--- a/src/papod.clj
+++ b/src/papod.clj
@@ -1225,9 +1225,28 @@
                                   " :You have " (count memos)
                                   " unread memo(s)."
                                   " Use /msg MemoServ LIST")])
-                rejoins (auto-rejoin-replies client components)]
+                rejoins (auto-rejoin-replies client components)
+                pending (:pending-metadata @client)
+                meta-burst
+                (when (seq pending)
+                  (let [bid (str (java.util.UUID/randomUUID))
+                        nlow (string/lower-case nick)]
+                    (when-let [meta-atom (:metadata components)]
+                      (swap! meta-atom update nlow
+                             (fnil into {}) pending))
+                    (swap! client dissoc :pending-metadata)
+                    (concat
+                     [(str "BATCH +" bid " metadata " nick)]
+                     (map
+                      (fn [[k v]]
+                        (str "@batch=" bid
+                             " :" +server-name+
+                             " METADATA " nick " " k
+                             " * :" v))
+                      (sort-by first pending))
+                     [(str "BATCH -" bid)])))]
             (notify-monitors! components nick "730")
-            (vec (concat welcome memo-line rejoins)))))))
+            (vec (concat welcome memo-line meta-burst rejoins)))))))
 
 (defn- valid-nick?
   [s]
@@ -1439,7 +1458,7 @@
                      reg-cap
                      " draft/channel-rename"
                      " draft/extended-isupport"
-                     " draft/metadata-2"
+                     " draft/metadata-2=before-connect"
                      " draft/typing")
                 (str "sasl message-tags server-time"
                      " echo-message batch"
@@ -3800,8 +3819,96 @@
     (client-target client)
     requested))
 
+(defn- pending-metadata-handler
+  "Handles METADATA SET/GET/LIST/CLEAR before registration completes
+  (draft/metadata-2 before-connect). Values are buffered in the
+  client atom until the welcome burst replays them."
+  [params client]
+  (let [target (first params)
+        subcmd (when (> (count params) 1)
+                 (string/upper-case (second params)))
+        rest-args (drop 2 params)]
+    (cond
+      (or (nil? target) (string/blank? target))
+      [(numeric-reply client "461"
+         "METADATA :Not enough parameters")]
+
+      (nil? subcmd)
+      [(numeric-reply client "461"
+         "METADATA :Not enough parameters")]
+
+      ;; Only "*" target makes sense pre-registration.
+      (not= target "*")
+      [(str "FAIL METADATA INVALID_TARGET "
+            target " :Invalid target")]
+
+      :else
+      (case subcmd
+        "GET"
+        (let [keys-asked (vec rest-args)
+              cur (or (:pending-metadata @client) {})]
+          (mapv
+           (fn [k]
+             (if-let [v (get cur k)]
+               (numeric-reply client "761"
+                 (str "* " k " * :" v))
+               (numeric-reply client "766"
+                 (str "* " k
+                      " :no matching key"))))
+           keys-asked))
+
+        "LIST"
+        (let [cur (or (:pending-metadata @client) {})]
+          (mapv
+           (fn [[k v]]
+             (numeric-reply client "761"
+               (str "* " k " * :" v)))
+           (sort-by first cur)))
+
+        "SET"
+        (let [k (first rest-args)
+              v-parts (rest rest-args)
+              raw-v (when (seq v-parts)
+                      (string/join " " v-parts))
+              v (when raw-v
+                  (cond-> raw-v
+                    (string/starts-with? raw-v ":") (subs 1)))
+              v-bytes (when v
+                        (alength (.getBytes ^String v "UTF-8")))]
+          (cond
+            (nil? k)
+            [(numeric-reply client "461"
+               "METADATA :Not enough parameters")]
+
+            (and v-bytes (> v-bytes 360))
+            [(str "FAIL METADATA VALUE_INVALID :Value of "
+                  k " is too long")]
+
+            (or (nil? v) (string/blank? v))
+            (do (swap! client update :pending-metadata
+                       (fnil dissoc {}) k)
+                [(numeric-reply client "766"
+                   (str "* " k " :no matching key"))])
+
+            :else
+            (do (swap! client update :pending-metadata
+                       (fnil assoc {}) k v)
+                [(numeric-reply client "761"
+                   (str "* " k " * :" v))])))
+
+        "CLEAR"
+        (do (swap! client assoc :pending-metadata {})
+            [(numeric-reply client "762"
+               "* :end of metadata")])
+
+        ;; SUB/UNSUB/SUBS pre-reg: not useful.
+        [(numeric-reply client "461"
+           "METADATA :Not enough parameters")]))))
+
 (defn- handle-metadata
   [params client components]
+  (if-not (:registered? @client)
+    (pending-metadata-handler params client)
   (let [nick    (client-target client)
         target  (first params)
         subcmd  (when (> (count params) 1)
@@ -3954,7 +4061,7 @@
                ":none"))])
 
         [(str "FAIL METADATA INVALID_SUBCOMMAND "
-              subcmd " :Unknown subcommand")]))))
+              subcmd " :Unknown subcommand")])))))
 
 (defn- handle-markread
   [params client components]
@@ -4936,6 +5043,7 @@
       "CAP"          (handle-cap params client components)
       "AUTHENTICATE" (handle-authenticate params client components)
       "REGISTER"     (handle-register params client components)
+      "METADATA"     (handle-metadata params client components)
       "BATCH"        (let [ref (first params)]
                        (cond
                          (and ref (string/starts-with? ref "+"))