FEATURE: Group logs.

app/models/group_history.rb

@@ -0,0 +1,72 @@
+class GroupHistory < ActiveRecord::Base
+  belongs_to :group
+  belongs_to :acting_user, class_name: 'User'
+  belongs_to :target_user, class_name: 'User'
+
+  validates :acting_user_id, presence: true
+  validates :group_id, presence: true
+  validates :action, presence: true
+
+  def self.actions
+    @actions ||= Enum.new(
+      change_group_setting: 1,
+      add_user_to_group: 2,
+      remove_user_from_group: 3,
+      make_user_group_owner: 4,
+      remove_user_as_group_owner: 5
+    )
+  end
+
+  def self.filters
+    [
+      :acting_user,
+      :target_user,
+      :action,
+      :subject
+    ]
+  end
+
+  def self.with_filters(group, params = {})
+    records = self.includes(:acting_user, :target_user)
+      .where(group_id: group.id)
+      .order('group_histories.created_at DESC')
+
+    if !params.blank?
+      params = params.slice(*filters)
+      records = records.where(action: self.actions[params[:action].to_sym]) unless params[:action].blank?
+      records = records.where(subject: params[:subject]) unless params[:subject].blank?
+
+      [:acting_user, :target_user].each do |filter|
+        unless params[filter].blank?
+          id = User.where(username_lower: params[filter]).pluck(:id)
+          records = records.where("#{filter}_id" => id)
+        end
+      end
+    end
+
+    records
+  end
+end
+
+# == Schema Information
+#
+# Table name: group_histories
+#
+#  id             :integer          not null, primary key
+#  group_id       :integer          not null
+#  acting_user_id :integer          not null
+#  target_user_id :integer
+#  action         :integer          not null
+#  subject        :string
+#  prev_value     :text
+#  new_value      :text
+#  created_at     :datetime         not null
+#  updated_at     :datetime         not null
+#
+# Indexes
+#
+#  index_group_histories_on_acting_user_id  (acting_user_id)
+#  index_group_histories_on_action          (action)
+#  index_group_histories_on_group_id        (group_id)
+#  index_group_histories_on_target_user_id  (target_user_id)
+#