def self.search(agent, params)
  RealPropertySale.where(id: available_ids)
                      .joins(:address)
                      .by_state(state)
                      .by_suburb(suburb)
                      .by_post_code(post_code)
                      .by_country(country)
                      .paginate(page: page)
end

def self.by_state(state)
  where(addresses: {state: state})
end

def self.by_suburb(suburb)
  where(addresses: {suburb: suburb})
end

def self.by_post_code(post_code)
  where(addresses: {post_code: post_code})
end

def self.by_country(country)
  where(addresses: {country: country})
end

def self.by_state(state)
  return current_scope if state.nil?
  where(addresses: {state: state})
end