Remove unneeded code from the join method

app/controllers/groups_controller.rb

@@ -410,78 +410,24 @@ class GroupsController < ApplicationController
 
   def join
     group = Group.find(params[:id])
-    group.public_admission ? ensure_logged_in : guardian.ensure_can_edit!(group)
-    users = users_from_params.to_a
+    ensure_logged_in
 
-    if group.public_admission
-      if !guardian.can_log_group_changes?(group) && current_user != users.first
-        raise Discourse::InvalidAccess
-      end
+    raise Discourse::InvalidAccess unless group.public_admission
 
-      unless current_user.staff?
-        RateLimiter.new(current_user, "public_group_membership", 3, 1.minute).performed!
-      end
+    unless current_user.staff?
+      RateLimiter.new(current_user, "public_group_membership", 3, 1.minute).performed!
     end
 
-    emails = []
-    if params[:emails]
-      params[:emails].split(",").each do |email|
-        existing_user = User.find_by_email(email)
-        existing_user.present? ? users.push(existing_user) : emails.push(email)
-      end
-    end
+    already_in_group = group.users.exists?(id: current_user.id)
+    return if already_in_group
 
-    guardian.ensure_can_invite_to_forum!([group]) if emails.present?
-
-    if users.empty? && emails.empty?
-      raise Discourse::InvalidParameters.new(I18n.t("groups.errors.usernames_or_emails_required"))
-    end
-
-    if users.length > ADD_MEMBERS_LIMIT
-      return render_json_error(
-        I18n.t("groups.errors.adding_too_many_users", count: ADD_MEMBERS_LIMIT)
-      )
-    end
-
-    usernames_already_in_group = group.users.where(id: users.map(&:id)).pluck(:username)
-    if usernames_already_in_group.present? &&
-      usernames_already_in_group.length == users.length &&
-      emails.blank?
-      render_json_error(I18n.t(
-        "groups.errors.member_already_exist",
-        username: usernames_already_in_group.sort.join(", "),
-        count: usernames_already_in_group.size
-      ))
-    else
-      uniq_users = users.uniq
-      uniq_users.each do |user|
-        begin
-          group.add(user)
-          GroupActionLogger.new(current_user, group).log_add_user_to_group(user)
-          group.notify_added_to_group(user) if params[:notify_users]&.to_s == "true"
-        rescue ActiveRecord::RecordNotUnique
-          # Under concurrency, we might attempt to insert two records quickly and hit a DB
-          # constraint. In this case we can safely ignore the error and act as if the user
-          # was added to the group.
-        end
-      end
-
-      emails.each do |email|
-        begin
-          Invite.generate(current_user, email: email, group_ids: [group.id])
-        rescue RateLimiter::LimitExceeded => e
-          return render_json_error(I18n.t(
-            "invite.rate_limit",
-            count: SiteSetting.max_invites_per_day,
-            time_left: e.time_left
-          ))
-        end
-      end
-
-      render json: success_json.merge!(
-        usernames: uniq_users.map(&:username),
-        emails: emails
-      )
+    begin
+      group.add(current_user)
+      GroupActionLogger.new(current_user, group).log_add_user_to_group(current_user)
+    rescue ActiveRecord::RecordNotUnique
+      # Under concurrency, we might attempt to insert two records quickly and hit a DB
+      # constraint. In this case we can safely ignore the error and act as if the user
+      # was added to the group.
     end
   end