class HashSchema
  def initialize(schema)
    @schema = schema.map { |key, type|
      [key, HashSchema.lookup(type)]
    }.to_h
  end

  def cast(params)
    params.map { |key, value|
      [key, @schema[key] ? @schema[key].cast(value) : value]
    }.to_h
  end

  class << self
    def lookup(type)
      case type
      when Array  then ArraySchema.new(type[0])
      when Hash   then HashSchema.new(type)
      when Symbol then ActiveModel::Type.lookup(type)
      else             type
      end
    end
  end

  class ArraySchema
    def initialize(type)
      @type = HashSchema.lookup(type)
    end

    def cast(values)
      values.map { |value| @type.cast(value) }
    end
  end
end