class ReeMapper::FilterFieldsContract

def self.message(*)
  "Invalid filter fields contract"
end

def self.to_s
  "FilterFieldsContract"
end

def self.valid?(value)
  return false unless value.is_a? Array
  value.each do |item|
    next if item.is_a? Symbol
    return false unless item.is_a? Hash
    item.each do |key, val|
      return false unless key.is_a?(Symbol)
      return false unless valid?(val)
    end
  end
  true
end