fix: /ban messages for self/mod bans (#4164)

CHANGELOG.md

@@ -68,8 +68,8 @@
 - Minor: Migrated /followersoff to Helix API. (#4040)
 - Minor: Migrated /raid command to Helix API. Chat command will continue to be used until February 11th 2023. (#4029)
 - Minor: Migrated /unraid command to Helix API. Chat command will continue to be used until February 11th 2023. (#4030)
-- Minor: Migrated /ban to Helix API. (#4049)
+- Minor: Migrated /ban to Helix API. (#4049, #4164)
-- Minor: Migrated /timeout to Helix API. (#4049)
+- Minor: Migrated /timeout to Helix API. (#4049, #4164)
 - Minor: Migrated /w to Helix API. Chat command will continue to be used until February 11th 2023. (#4052)
 - Minor: Migrated /vips to Helix API. Chat command will continue to be used until February 11th 2023. (#4053)
 - Minor: Migrated /uniquechat and /r9kbeta to Helix API. (#4057)

src/controllers/commands/CommandController.cpp

@@ -2658,11 +2658,22 @@ void CommandController::initialize(Settings &, Paths &paths)
 
             case Error::TargetBanned: {
                 // Equivalent IRC error
-                errorMessage = QString("%1 is already banned in this channel.")
+                errorMessage += QString("%1 is already banned in this channel.")
                                     .arg(userDisplayName);
             }
             break;
 
+            case Error::CannotBanUser: {
+                // We can't provide the identical error as in IRC,
+                // because we don't have enough information about the user.
+                // The messages from IRC are formatted like this:
+                // "You cannot {op} moderator {mod} unless you are the owner of this channel."
+                // "You cannot {op} the broadcaster."
+                errorMessage += QString("You cannot %1 %2.")
+                                    .arg(operation, userDisplayName);
+            }
+            break;
+
             case Error::UserMissingScope: {
                 // TODO(pajlada): Phrase MISSING_REQUIRED_SCOPE
                 errorMessage += "Missing required scope. "

src/providers/twitch/api/Helix.cpp

@@ -2064,6 +2064,13 @@ void Helix::banUser(QString broadcasterID, QString moderatorID, QString userID,
                     {
                         failureCallback(Error::TargetBanned, message);
                     }
+                    else if (message.startsWith(
+                                 "The user specified in the user_id field may "
+                                 "not be banned",
+                                 Qt::CaseInsensitive))
+                    {
+                        failureCallback(Error::CannotBanUser, message);
+                    }
                     else
                     {
                         failureCallback(Error::Forwarded, message);

src/providers/twitch/api/Helix.hpp

@@ -551,6 +551,7 @@ enum class HelixBanUserError {  // /timeout, /ban
     Ratelimited,
     ConflictingOperation,
     TargetBanned,
+    CannotBanUser,
 
     // The error message is forwarded directly from the Twitch API
     Forwarded,