Add channel_join script command (#7970)

doc/script_commands.txt

@@ -11140,6 +11140,17 @@ Returns 1 on success.
 
 ---------------------------------------
 
+*channel_join "<channel_name>"{, <char_id>};
+
+Join an existing channel.
+The command returns 0 upon success, and these values upon failure:
+ -1 : Invalid channel or player
+ -2 : Player already in channel
+ -3 : Player banned
+ -4 : Reached max limit
+
+---------------------------------------
+
 *channel_setopt "<chname>",<option>,<value>;
 
 Set option for the channel. Use 1 in <value> to set it, or 0 to unset.

src/map/script.cpp

@@ -24656,6 +24656,37 @@ BUILDIN_FUNC(channel_create) {
 	return SCRIPT_CMD_SUCCESS;
 }
 
+// ===================================
+// *channel_join "<channel_name>"{, <char_id>};
+// Join an existing channel.
+// The command returns 0 upon success, and these values upon failure:
+// -1 : Invalid channel or player
+// -2 : Player already in channel
+// -3 : Player banned
+// -4 : Reached max limit
+// ===================================
+BUILDIN_FUNC(channel_join) {
+	map_session_data *sd = nullptr;
+
+	if (!script_charid2sd(3, sd)) {
+		script_pushint(st, -1);
+		return SCRIPT_CMD_FAILURE;
+	}
+
+	struct Channel *channel = nullptr;
+	const char *chname = script_getstr(st, 2);
+
+	if (!(channel = channel_name2channel((char *)chname, nullptr, 0))) {
+		ShowError("buildin_channel_join: Channel name '%s' is invalid.\n", chname);
+		script_pushint(st, -1);
+		return SCRIPT_CMD_FAILURE;
+	}
+
+	script_pushint(st, channel_join(channel, sd));
+
+	return SCRIPT_CMD_SUCCESS;
+}
+
 /**
  * Set channel option
  * channel_setopt "<chname>",<option>,<value>;
@@ -27634,6 +27665,7 @@ struct script_function buildin_func[] = {
 
 	// Channel System
 	BUILDIN_DEF(channel_create,"ss?????"),
+	BUILDIN_DEF(channel_join, "s?"),
 	BUILDIN_DEF(channel_setopt,"sii"),
 	BUILDIN_DEF(channel_getopt,"si"),
 	BUILDIN_DEF(channel_setcolor,"si"),