class HTTP::Options

def []=(option, val)
  send(:"#{option}=", val)
end

def argument_error!(message)
  raise(Error, message, caller(1..-1))
end

def def_option(name, reader_only: false, &interpreter)
  defined_options << name.to_sym
  interpreter ||= ->(v) { v }
  if reader_only
    attr_reader name
  else
    attr_accessor name
    protected :"#{name}="
  end
  define_method(:"with_#{name}") do |value|
    dup { |opts| opts.send(:"#{name}=", instance_exec(value, &interpreter)) }
  end
end

def defined_options
  @defined_options ||= []
end

def dup
  dupped = super
  yield(dupped) if block_given?
  dupped
end

def feature(name)
  features[name]
end

def features=(features)
  @features = features.each_with_object({}) do |(name, opts_or_feature), h|
    h[name] = if opts_or_feature.is_a?(Feature)
                opts_or_feature
              else
                unless (feature = self.class.available_features[name])
                  argument_error! "Unsupported feature: #{name}"
                end
                feature.new(**opts_or_feature)
              end
  end
end

def follow=(value)
  @follow =
    case
    when !value                    then nil
    when true == value             then {}
    when value.respond_to?(:fetch) then value
    else argument_error! "Unsupported follow options: #{value}"
    end
end

def initialize(options = {})
  defaults = {
    :response           => :auto,
    :proxy              => {},
    :timeout_class      => self.class.default_timeout_class,
    :timeout_options    => {},
    :socket_class       => self.class.default_socket_class,
    :nodelay            => false,
    :ssl_socket_class   => self.class.default_ssl_socket_class,
    :ssl                => {},
    :keep_alive_timeout => 5,
    :headers            => {},
    :cookies            => {},
    :encoding           => nil,
    :features           => {}
  }
  opts_w_defaults = defaults.merge(options)
  opts_w_defaults[:headers] = HTTP::Headers.coerce(opts_w_defaults[:headers])
  opts_w_defaults.each { |(k, v)| self[k] = v }
end

def merge(other)
  h1 = to_hash
  h2 = other.to_hash
  merged = h1.merge(h2) do |k, v1, v2|
    case k
    when :headers
      v1.merge(v2)
    else
      v2
    end
  end
  self.class.new(merged)
end

def new(options = {})
  options.is_a?(self) ? options : super
end

def persistent=(value)
  @persistent = value ? HTTP::URI.parse(value).origin : nil
end

def persistent?
  !persistent.nil?
end

def register_feature(name, impl)
  @available_features[name] = impl
end

def to_hash
  hash_pairs = self.class.
               defined_options.
               flat_map { |opt_name| [opt_name, send(opt_name)] }
  Hash[*hash_pairs]
end