Add the Create Channel dialog

The official client creates and edits channels with one dialog, so
ChannelEditDialog becomes ChannelDialog with two entry points. Creating
starts from caller-chosen defaults instead of a channelinfo and sends a
channelcreate carrying only what deviates from a plain new channel —
TeamSpeak checks a create permission per property that is present.

The server row now has a context menu with "Create Channel" and "Create
Spacer" (pre-filled with the lowest free [spacerN], since channel names
must be unique), and a channel's menu offers "Create Channel" and
"Create Sub-Channel", both starting out temporary.

Verified against the test server: a temporary channel is created, and a
permanent one a guest may not create reports the server's refusal.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ts3-client/core/src/main/java/com/ts3client/net/ChannelAdmin.java

@@ -58,6 +58,31 @@ final class ChannelAdmin {
         return ChannelSettings.from(channelId, info.getMap());
     }
 
+    /**
+     * Creates a channel below {@code parentId} (0 being the top level).
+     *
+     * @param properties the new channel's properties, as {@link ChannelSettings#creationParameters}
+     * @return the new channel's id
+     */
+    int create(int parentId, Map<String, String> properties) throws Exception {
+        SingleCommand cmd = new SingleCommand("channelcreate", ProtocolRole.CLIENT);
+        cmd.add(new CommandSingleParameter("cpid", Integer.toString(parentId)));
+        for (Map.Entry<String, String> property : properties.entrySet()) {
+            cmd.add(new CommandSingleParameter(property.getKey(), property.getValue()));
+        }
+        for (SingleCommand answer : conn.socket().executeCommand(cmd).get()) {
+            int cid = parseInt(answer.toMap().get("cid"), -1);
+            if (cid > 0) return cid;
+        }
+        // Some servers acknowledge the command without naming the channel; the
+        // notifychannelcreated they also send does name it, so read it off the model
+        // once that event has been handled.
+        conn.awaitEventsProcessed();
+        ChannelNode created = conn.getModel().findChannelByName(parentId, properties.get("channel_name"));
+        if (created == null) throw new IllegalStateException("The server did not report the new channel");
+        return created.id;
+    }
+
     /** Applies {@code changes} (property name to value) with a single {@code channeledit}. */
     void edit(int channelId, Map<String, String> changes) throws Exception {
         if (changes.isEmpty()) return;

ts3-client/core/src/main/java/com/ts3client/net/ChannelSettings.java

@@ -143,6 +143,32 @@ public final class ChannelSettings {
         return changes;
     }
 
+    /**
+     * The {@code channelcreate} parameters for a channel that does not exist yet.
+     *
+     * <p>Everything a fresh channel would get anyway is left out, because TeamSpeak checks
+     * a create permission per property that is present — a client allowed to create plain
+     * channels but not, say, ones with a topic must not send an empty topic. What the
+     * server cannot infer is always sent: the name, the channel type (whose absent flags
+     * would silently mean temporary), the codec, and the client limits when they are not
+     * unlimited.
+     */
+    public Map<String, String> creationParameters() {
+        Map<String, String> params = changesFrom(new ChannelSettings());
+        params.put("channel_name", name);
+        params.put("channel_flag_permanent", flag(type == Type.PERMANENT));
+        params.put("channel_flag_semi_permanent", flag(type == Type.SEMI_PERMANENT));
+        params.put("channel_flag_temporary", flag(type == Type.TEMPORARY));
+        params.put("channel_codec", Integer.toString(codec));
+        params.put("channel_codec_quality", Integer.toString(codecQuality));
+        if (!maxClientsUnlimited) params.put("channel_maxclients", Integer.toString(maxClients));
+        if (!familyInherited && !familyUnlimited) {
+            params.put("channel_maxfamilyclients", Integer.toString(maxFamilyClients));
+        }
+        if (password == null || password.isEmpty()) params.remove("channel_password");
+        return params;
+    }
+
     private static void putIfChanged(Map<String, String> into, String key, String value, String was) {
         if (!value.equals(was)) into.put(key, value);
     }

ts3-client/core/src/main/java/com/ts3client/net/ServerModel.java

@@ -218,17 +218,34 @@ public final class ServerModel {
     public synchronized List<ChannelNode> siblingsOf(int channelId) {
         ChannelNode channel = channels.get(channelId);
         if (channel == null) return new ArrayList<>();
-        List<ChannelNode> siblings = new ArrayList<>();
-        for (ChannelNode c : channels.values()) {
-            if (c.parentId == channel.parentId) siblings.add(c);
-        }
         // Ordered with the channel still in place: the order links form a chain, and
         // pulling a link out of it first would strand everything below.
-        sortSiblings(siblings);
+        List<ChannelNode> siblings = childrenOf(channel.parentId);
         siblings.remove(channel);
         return siblings;
     }
 
+    /**
+     * The channels directly below {@code parentId} (0 being the top level), in the order
+     * they appear in the tree — what a new channel can be sorted after.
+     */
+    public synchronized List<ChannelNode> childrenOf(int parentId) {
+        List<ChannelNode> children = new ArrayList<>();
+        for (ChannelNode c : channels.values()) {
+            if (c.parentId == parentId) children.add(c);
+        }
+        sortSiblings(children);
+        return children;
+    }
+
+    /** The channel of that exact name directly below {@code parentId}, or {@code null}. */
+    public synchronized ChannelNode findChannelByName(int parentId, String name) {
+        for (ChannelNode c : channels.values()) {
+            if (c.parentId == parentId && c.name.equals(name)) return c;
+        }
+        return null;
+    }
+
     /** The "/"-separated path of a channel from the root, e.g. {@code "Lobby/Games"}. */
     public synchronized String channelPath(int id) {
         ChannelNode c = channels.get(id);

ts3-client/core/src/main/java/com/ts3client/net/TeamspeakConnection.java

@@ -923,6 +923,29 @@ public final class TeamspeakConnection implements TS3Listener {
         });
     }
 
+    /**
+     * Creates a channel below {@code parentId} (0 being the top level) and gives it the
+     * channel permissions it was created with.
+     *
+     * @param callback given the new channel's id, or the failure message. A channel whose
+     *                 permissions could not be set still exists, and is reported as an error
+     *                 saying so.
+     */
+    public void createChannel(int parentId, Map<String, String> properties,
+                              Map<String, Integer> permissions,
+                              BiConsumer<Integer, String> callback) {
+        run("ts3j-channel-create", callback, () -> {
+            int channelId = channels.create(parentId, properties);
+            try {
+                channels.writePermissions(channelId, permissions, List.of());
+            } catch (Exception e) {
+                throw new IllegalStateException("The channel was created, but its permissions"
+                        + " could not be set: " + rootMessage(e));
+            }
+            return channelId;
+        });
+    }
+
     /** The ids of the icons uploaded to this virtual server. */
     public void requestServerIcons(BiConsumer<List<Long>, String> callback) {
         run("ts3j-icon-list", callback, channels::listIcons);