# Store object full path in separate table for easy lookup and uniq validation
# Object must have name and path db fields and respond to parent and parent_changed? methods.
module Routable
  extend ActiveSupport::Concern

  included do
    has_one :route, as: :source, autosave: true, dependent: :destroy

    validates_associated :route
    validates :route, presence: true

    scope :with_route, -> { includes(:route) }

    before_validation do
      if full_path_changed? || full_name_changed?
        prepare_route
      end
    end
  end

  class_methods do
    # Finds a single object by full path match in routes table.
    #
    # Usage:
    #
    #     Klass.find_by_full_path('gitlab-org/gitlab-ce')
    #
    # Returns a single object, or nil.
    def find_by_full_path(path)
      # On MySQL we want to ensure the ORDER BY uses a case-sensitive match so
      # any literal matches come first, for this we have to use "BINARY".
      # Without this there's still no guarantee in what order MySQL will return
      # rows.
      binary = Gitlab::Database.mysql? ? 'BINARY' : ''

      order_sql = "(CASE WHEN #{binary} routes.path = #{connection.quote(path)} THEN 0 ELSE 1 END)"

      where_full_path_in([path]).reorder(order_sql).take
    end

    # Builds a relation to find multiple objects by their full paths.
    #
    # Usage:
    #
    #     Klass.where_full_path_in(%w{gitlab-org/gitlab-ce gitlab-org/gitlab-ee})
    #
    # Returns an ActiveRecord::Relation.
    def where_full_path_in(paths)
      wheres = []
      cast_lower = Gitlab::Database.postgresql?

      paths.each do |path|
        path = connection.quote(path)

        where =
          if cast_lower
            "(LOWER(routes.path) = LOWER(#{path}))"
          else
            "(routes.path = #{path})"
          end

        wheres << where
      end

      if wheres.empty?
        none
      else
        joins(:route).where(wheres.join(' OR '))
      end
    end

    # Builds a relation to find multiple objects that are nested under user membership
    #
    # Usage:
    #
    #     Klass.member_descendants(1)
    #
    # Returns an ActiveRecord::Relation.
    def member_descendants(user_id)
      joins(:route).
        joins("INNER JOIN routes r2 ON routes.path LIKE CONCAT(r2.path, '/%')
               INNER JOIN members ON members.source_id = r2.source_id
               AND members.source_type = r2.source_type").
        where('members.user_id = ?', user_id)
    end

    # Builds a relation to find multiple objects that are nested under user
    # membership. Includes the parent, as opposed to `#member_descendants`
    # which only includes the descendants.
    #
    # Usage:
    #
    #     Klass.member_self_and_descendants(1)
    #
    # Returns an ActiveRecord::Relation.
    def member_self_and_descendants(user_id)
      joins(:route).
        joins("INNER JOIN routes r2 ON routes.path LIKE CONCAT(r2.path, '/%')
               OR routes.path = r2.path
               INNER JOIN members ON members.source_id = r2.source_id
               AND members.source_type = r2.source_type").
        where('members.user_id = ?', user_id)
    end

    # Returns all objects in a hierarchy, where any node in the hierarchy is
    # under the user membership.
    #
    # Usage:
    #
    #     Klass.member_hierarchy(1)
    #
    # Examples:
    #
    #     Given the following group tree...
    #
    #            _______group_1_______
    #           |                     |
    #           |                     |
    #     nested_group_1        nested_group_2
    #           |                     |
    #           |                     |
    #     nested_group_1_1      nested_group_2_1
    #
    #
    #     ... the following results are returned:
    #
    #     * the user is a member of group 1
    #       => 'group_1',
    #          'nested_group_1', nested_group_1_1',
    #          'nested_group_2', 'nested_group_2_1'
    #
    #     * the user is a member of nested_group_2
    #       => 'group1',
    #          'nested_group_2', 'nested_group_2_1'
    #
    #     * the user is a member of nested_group_2_1
    #       => 'group1',
    #          'nested_group_2', 'nested_group_2_1'
    #
    # Returns an ActiveRecord::Relation.
    def member_hierarchy(user_id)
      paths = member_self_and_descendants(user_id).pluck('routes.path')

      return none if paths.empty?

      wheres = paths.map do |path|
        "#{connection.quote(path)} = routes.path
         OR
         #{connection.quote(path)} LIKE CONCAT(routes.path, '/%')"
      end

      joins(:route).where(wheres.join(' OR '))
    end
  end

  def full_name
    if route && route.name.present?
      @full_name ||= route.name
    else
      update_route if persisted?

      build_full_name
    end
  end

  def full_path
    if route && route.path.present?
      @full_path ||= route.path
    else
      update_route if persisted?

      build_full_path
    end
  end

  private

  def full_name_changed?
    name_changed? || parent_changed?
  end

  def full_path_changed?
    path_changed? || parent_changed?
  end

  def build_full_name
    if parent && name
      parent.human_name + ' / ' + name
    else
      name
    end
  end

  def build_full_path
    if parent && path
      parent.full_path + '/' + path
    else
      path
    end
  end

  def update_route
    prepare_route
    route.save
  end

  def prepare_route
    route || build_route(source: self)
    route.path = build_full_path
    route.name = build_full_name
    @full_path = nil
    @full_name = nil
  end
end