hash.rb

{
  nil => "No se encuentra",
  'A' => "Opción A",
  'X' => AMOUNT * RATE
}

ORDER_TO_BD = {
  'cheap' => 'price',
  'expensive' => 'price DESC',
  'popular' => 'likes_count DESC'
}
order = ORDER_TO_BD[param_order] || 'created_at DESC'

PROVINCIA_API = {
  'La Coruña' => 'A Coruña',
  'Gerona' => 'Girona'
}
provincia = PROVINCIA_API[provincia_api] || provincia_api

DEFAULT_PAGINATE = {
  page: 1,
  per_page: 25,
  order: 'created_at',
  total_entries: 1000
}

def pagination(custom_pagination = {})
  options = DEFAULT_PAGINATE.merge(custom_pagination)
  first = 1 + (options[:page] - 1) * options[:per_page]
  ...
end