class Faraday::Options

def self.attribute_options
  @attribute_options ||= {}
end

def self.fetch_error_class
  @fetch_error_class ||= if Object.const_defined?(:KeyError)
    ::KeyError
  else
    ::IndexError
  end
end

def self.from(value)
  value ? new.update(value) : new
end

def self.inherited(subclass)
  super
  subclass.attribute_options.update(attribute_options)
  subclass.memoized_attributes.update(memoized_attributes)
end

def self.memoized(key)
  memoized_attributes[key.to_sym] = Proc.new
  class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def #{key}() self[:#{key}]; end
  RUBY
end

def self.memoized_attributes
  @memoized_attributes ||= {}
end

def self.options(mapping)
  attribute_options.update(mapping)
end

def self.options_for(key)
  attribute_options[key]
end

def [](key)
  key = key.to_sym
  if method = self.class.memoized_attributes[key]
    super(key) || (self[key] = instance_eval(&method))
  else
    super
  end
end

def clear
  members.each { |member| delete(member) }
end

def deep_dup
  self.class.from(self)
end

def delete(key)
  value = send(key)
  send("#{key}=", nil)
  value
end

def each
  return to_enum(:each) unless block_given?
  members.each do |key|
    yield(key.to_sym, send(key))
  end
end

def each_key
  return to_enum(:each_key) unless block_given?
  keys.each do |key|
    yield(key)
  end
end

def each_value
  return to_enum(:each_value) unless block_given?
  values.each do |value|
    yield(value)
  end
end

def empty?
  keys.empty?
end

def fetch(key, *args)
  unless symbolized_key_set.include?(key.to_sym)
    key_setter = "#{key}="
    if args.size > 0
      send(key_setter, args.first)
    elsif block_given?
      send(key_setter, Proc.new.call(key))
    else
      raise self.class.fetch_error_class, "key not found: #{key.inspect}"
    end
  end
  send(key)
end

def inspect
  values = []
  members.each do |member|
    value = send(member)
    values << "#{member}=#{value.inspect}" if value
  end
  values = values.empty? ? ' (empty)' : (' ' << values.join(", "))
  %(#<#{self.class}#{values}>)
end

def key?(key)
  keys.include?(key)
end

def keys
  members.reject { |member| send(member).nil? }
end

def merge(other)
  dup.merge!(other)
end

def merge!(other)
  other.each do |key, other_value|
    self_value = self.send(key)
    sub_options = self.class.options_for(key)
    new_value = (self_value && sub_options && other_value) ? self_value.merge(other_value) : other_value
    self.send("#{key}=", new_value) unless new_value.nil?
  end
  self
end

def symbolized_key_set
  @symbolized_key_set ||= Set.new(keys.map { |k| k.to_sym })
end

def to_hash
  hash = {}
  members.each do |key|
    value = send(key)
    hash[key.to_sym] = value unless value.nil?
  end
  hash
end

def update(obj)
  obj.each do |key, value|
    sub_options = self.class.options_for(key)
    if sub_options
      new_value = sub_options.from(value) if value
    elsif value.is_a?(Hash)
      new_value = value.dup
    else
      new_value = value
    end
    self.send("#{key}=", new_value) unless new_value.nil?
  end
  self
end

def value?(value)
  values.include?(value)
end

def values_at(*keys)
  keys.map { |key| send(key) }
end