FIX: ensures users can open channel invites (#24067)

We were incorrectly generating URLs with message id even when it was not provided, resulting in a route ending with "undefined", which was causing an error.

This commit also uses this opportunity to:
- move `invite_users` into a proper controller inside the API namespace
- refactors the code into a service: `Chat::InviteUsersToChannel`

plugins/chat/app/controllers/chat/api/channels_invites_controller.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class Chat::Api::ChannelsInvitesController < Chat::ApiController
+  def create
+    with_service(Chat::InviteUsersToChannel) do
+      on_failed_policy(:can_view_channel) { raise Discourse::InvalidAccess }
+      on_model_not_found(:channel) { raise Discourse::NotFound }
+    end
+  end
+end

plugins/chat/app/controllers/chat/chat_controller.rb

@@ -114,37 +114,6 @@ module Chat
       render json: { chat_enabled: current_user.user_option.chat_enabled }
     end
 
-    def invite_users
-      params.require(:user_ids)
-
-      users =
-        User
-          .includes(:groups)
-          .joins(:user_option)
-          .where(user_options: { chat_enabled: true })
-          .not_suspended
-          .where(id: params[:user_ids])
-      users.each do |user|
-        if user.guardian.can_join_chat_channel?(@chat_channel)
-          data = {
-            message: "chat.invitation_notification",
-            chat_channel_id: @chat_channel.id,
-            chat_channel_title: @chat_channel.title(user),
-            chat_channel_slug: @chat_channel.slug,
-            invited_by_username: current_user.username,
-          }
-          data[:chat_message_id] = params[:chat_message_id] if params[:chat_message_id]
-          user.notifications.create(
-            notification_type: Notification.types[:chat_invitation],
-            high_priority: true,
-            data: data.to_json,
-          )
-        end
-      end
-
-      render json: success_json
-    end
-
     def dismiss_retention_reminder
       params.require(:chatable_type)
       guardian.ensure_can_chat!

plugins/chat/app/services/chat/create_thread.rb

@@ -9,7 +9,7 @@ module Chat
   class CreateThread
     include Service::Base
 
-    # @!method call(thread_id:, channel_id:, guardian:, **params_to_edit)
+    # @!method call(thread_id:, channel_id:, guardian:, **params_to_create)
     #   @param [Integer] original_message_id
     #   @param [Integer] channel_id
     #   @param [Guardian] guardian

plugins/chat/app/services/chat/invite_users_to_channel.rb

@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+module Chat
+  # Invites users to a channel.
+  #
+  # @example
+  #  Chat::InviteUsersToChannel.call(channel_id: 2, user_ids: [2, 43], guardian: guardian, **optional_params)
+  #
+  class InviteUsersToChannel
+    include Service::Base
+
+    # @!method call(user_ids:, channel_id:, guardian:)
+    #   @param [Array<Integer>] user_ids
+    #   @param [Integer] channel_id
+    #   @param [Guardian] guardian
+    #   @option optional_params [Integer, nil] message_id
+    #   @return [Service::Base::Context]
+
+    contract
+    model :channel
+    policy :can_view_channel
+    model :users, optional: true
+    step :send_invite_notifications
+
+    # @!visibility private
+    class Contract
+      attribute :user_ids, :array
+      validates :user_ids, presence: true
+
+      attribute :channel_id, :integer
+      validates :channel_id, presence: true
+
+      attribute :message_id, :integer
+    end
+
+    private
+
+    def fetch_channel(contract:, **)
+      ::Chat::Channel.find_by(id: contract.channel_id)
+    end
+
+    def can_view_channel(guardian:, channel:, **)
+      guardian.can_preview_chat_channel?(channel)
+    end
+
+    def fetch_users(contract:, **)
+      ::User
+        .joins(:user_option)
+        .where(user_options: { chat_enabled: true })
+        .not_suspended
+        .where(id: contract.user_ids)
+        .limit(50)
+    end
+
+    def send_invite_notifications(channel:, guardian:, users:, contract:, **)
+      users&.each do |invited_user|
+        next if !invited_user.guardian.can_join_chat_channel?(channel)
+
+        data = {
+          message: "chat.invitation_notification",
+          chat_channel_id: channel.id,
+          chat_channel_title: channel.title(invited_user),
+          chat_channel_slug: channel.slug,
+          invited_by_username: guardian.user.username,
+        }
+        data[:chat_message_id] = contract.message_id if contract.message_id
+
+        invited_user.notifications.create(
+          notification_type: ::Notification.types[:chat_invitation],
+          high_priority: true,
+          data: data.to_json,
+        )
+      end
+    end
+  end
+end