Implement FilteringService

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/services/filtering_service.rb

+# FilteringService class
+#
+# Used to filter Issues and MergeRequests collections by set of params
+#
+# Arguments:
+#   klass - actual class like Issue or MergeRequest
+#   current_user - which user use
+#   params:
+#     scope: 'created-by-me' or 'assigned-to-me' or 'all'
+#     state: 'open' or 'closed' or 'all'
+#     group_id: integer
+#     project_id: integer
+#     milestone_id: integer
+#     assignee_id: integer
+#     search: string
+#     label_name: string
+#     sort: string
+#
+class FilteringService
+  attr_accessor :klass, :current_user, :params
+
+  def execute(klass, current_user, params)
+    @klass = klass
+    @current_user = current_user
+    @params = params
+
+    items = by_scope
+    items = by_state(items)
+    items = by_group(items)
+    items = by_project(items)
+    items = by_search(items)
+    items = by_milestone(items)
+    items = by_assignee(items)
+    items = by_label(items)
+    items = sort(items)
+  end
+
+  private
+
+  def by_scope
+    table_name = klass.table_name
+
+    case params[:scope]
+    when 'created-by-me', 'authored' then
+      current_user.send(table_name)
+    when 'all' then
+      klass.of_projects(current_user.authorized_projects.pluck(:id))
+    when 'assigned-to-me' then
+      current_user.send("assigned_#{table_name}")
+    else
+      raise 'You must specify default scope'
+    end
+  end
+
+  def by_state(items)
+    case params[:state]
+    when 'closed'
+      items.closed
+    when 'all'
+      items
+    when 'opened'
+      items.opened
+    else
+      raise 'You must specify default state'
+    end
+  end
+
+  def by_group(items)
+    if params[:group_id].present?
+      items = items.of_group(Group.find(params[:group_id]))
+    end
+
+    items
+  end
+
+  def by_project(items)
+    if params[:project_id].present?
+      items = items.of_projects(params[:project_id])
+    end
+
+    items
+  end
+
+  def by_search(items)
+    if params[:search].present?
+      items = items.search(params[:search])
+    end
+
+    items
+  end
+
+  def sort(items)
+    items.sort(params[:sort])
+  end
+
+  def by_milestone(items)
+    if params[:milestone_id].present?
+      items = items.where(milestone_id: (params[:milestone_id] == '0' ? nil : params[:milestone_id]))
+    end
+
+    items
+  end
+
+  def by_assignee(items)
+    if params[:assignee_id].present?
+      items = items.where(assignee_id: (params[:assignee_id] == '0' ? nil : params[:assignee_id]))
+    end
+
+    items
+  end
+
+  def by_label(items)
+    if params[:label_name].present?
+      items = items.tagged_with(params[:label_name])
+    end
+
+    items
+  end
+end