# TodosFinder
#
# Used to filter Todos by set of params
#
# Arguments:
#   current_user - which user use
#   params:
#     action_id: integer
#     author_id: integer
#     project_id; integer
#     state: 'pending' (default) or 'done'
#     type: 'Issue' or 'MergeRequest'
#

class TodosFinder
  NONE = '0'.freeze

  attr_accessor :current_user, :params

  def initialize(current_user, params = {})
    @current_user = current_user
    @params = params
  end

  def execute
    items = current_user.todos
    items = include_associations(items)
    items = by_action_id(items)
    items = by_action(items)
    items = by_author(items)
    items = by_state(items)
    items = by_type(items)
    # Filtering by project HAS TO be the last because we use
    # the project IDs yielded by the todos query thus far
    items = by_project(items)

    sort(items)
  end

  private

  def include_associations(items)
    return items unless params[:include_associations]

    items.includes(
      [
        target: { project: [:route, namespace: :route] },
        author: { namespace: :route },
      ]
    )
  end

  def action_id?
    action_id.present? && Todo::ACTION_NAMES.has_key?(action_id.to_i)
  end

  def action_id
    params[:action_id]
  end

  def to_action_id
    Todo::ACTION_NAMES.key(action.to_sym)
  end

  def action?
    action.present? && to_action_id
  end

  def action
    params[:action]
  end

  def author?
    params[:author_id].present?
  end

  def author
    return @author if defined?(@author)

    @author =
      if author? && params[:author_id] != NONE
        User.find(params[:author_id])
      else
        nil
      end
  end

  def project?
    params[:project_id].present?
  end

  def project
    return @project if defined?(@project)

    if project?
      @project = Project.find(params[:project_id])

      unless Ability.allowed?(current_user, :read_project, @project)
        @project = nil
      end
    else
      @project = nil
    end

    @project
  end

  def projects(items)
    item_project_ids = items.reorder(nil).select(:project_id)
    ProjectsFinder.new.execute(current_user, item_project_ids)
  end

  def type?
    type.present? && %w(Issue MergeRequest).include?(type)
  end

  def type
    params[:type]
  end

  def sort(items)
    params[:sort] ? items.sort(params[:sort]) : items.reorder(id: :desc)
  end

  def by_action(items)
    if action?
      items = items.where(action: to_action_id)
    end

    items
  end

  def by_action_id(items)
    if action_id?
      items = items.where(action: action_id)
    end

    items
  end

  def by_author(items)
    if author?
      items = items.where(author_id: author.try(:id))
    end

    items
  end

  def by_project(items)
    if project?
      items = items.where(project: project)
    else
      item_projects = projects(items)
      items = items.merge(item_projects).joins(:project)
    end

    items
  end

  def by_state(items)
    case params[:state].to_s
    when 'done'
      items.done
    else
      items.pending
    end
  end

  def by_type(items)
    if type?
      items = items.where(target_type: type)
    end

    items
  end
end