class AWS::Core::Options::Validator

def format_error description, opt_name, context
  context = context || "option :#{opt_name}"
  raise ArgumentError, "expected #{description} for #{context}"
end

def initialize rules
  @rules = rules
end

def validate! request_options, rules = @rules
  # Verify all required options are present.
  rules.each_pair do |opt_name, opt_rules|
    if opt_rules[:required]
      unless request_options.key?(opt_name)
        raise ArgumentError, "missing required option #{opt_name.inspect}"
      end
    end
  end
  request_options.inject({}) do |options, (opt_name, value)|
    # Ensure this is a valid/accepted option
    unless rules.key?(opt_name)
      raise ArgumentError, "unexpected option #{opt_name.inspect}"
    end
    # Validate and convert the value
    valid_value = validate_value(rules[opt_name], value, opt_name)
    options.merge(opt_name => valid_value)
  end
end

def validate_array rules, value, opt_name, context = nil
  unless value.respond_to?(:each)
    format_error('enumerable value', opt_name, context)
  end
  values = []
  value.each do |v|
    context = "member #{values.size} of :#{opt_name}"
    values << validate_value(rules[:members], v, opt_name, context)
  end
  values
end

def validate_blob rules, value, opt_name, context = nil
  value
end

def validate_boolean rules, value, opt_name, context = nil
  unless [true, false].include?(value)
    format_error('true or false', opt_name, context)
  end
  value
end

def validate_hash rules, value, opt_name, context = nil
  unless value.respond_to?(:to_hash)
    format_error('hash value', opt_name, context)
  end
  validate!(value.to_hash, rules[:members])
end

def validate_integer rules, value, opt_name, context = nil
  unless value.respond_to?(:to_int)
    format_error('integer value', opt_name, context)
  end
  value.to_int
end

def validate_map rules, value, opt_name, context = nil
  unless value.respond_to?(:to_hash)
    format_error('hash value', opt_name, context)
  end
  value.inject({}) do |values,(k,v)|
    context = "member #{k.inspect} of :#{opt_name}"
    values[k] = validate_value(rules[:members], v, opt_name, context)
    values
  end
end

def validate_string rules, value, opt_name, context = nil
  unless value.respond_to?(:to_str)
    format_error('string value', opt_name, context)
  end
  rules[:lstrip] ?
    value.to_str.sub(/^#{rules[:lstrip]}/, '') :
    value.to_str
end

def validate_timestamp rules, value, opt_name, context = nil
  # TODO : add validation to timestamps values
  value.to_s
end

def validate_value *args
  send("validate_#{args.first[:type]}", *args)
end