module Rafters::Component
  extend ActiveSupport::Concern

  attr_writer :controller
  attr_reader :identifier

  included do
    attributes :settings, :identifier
  end

  def initialize(options = {})
    raise IdentifierMissing unless options.has_key?(:as)

    @source = if options.has_key?(:source)
      options.delete(:source).constantize.new(self)
    end

    @identifier = options.delete(:as)
    @settings = options.delete(:settings) || {}
  end

  def name
    self.class.name.underscore
  end

  def source
    if @source.nil?
      raise SourceMissing
    else
      @source
    end
  end

  def template_name
    @_template_name ||= begin
      _template_name = (self.class._template_name || self.class.name.underscore)
      _template_name = _template_name.call(self) if _template_name.is_a?(Proc)
      _template_name
    end
  end

  def attributes
    return {} if self.class._attributes.nil?

    @_attributes ||= Hashie::Mash.new.tap do |_attributes|
      (self.class._attributes || []).each do |name|
        _attributes[name] = send(name)
      end
    end
  end

  def settings
    @_settings ||= Hashie::Mash.new(defaults.merge(@settings).merge(overrides))
  end

  def defaults
    @_defaults ||= Hashie::Mash.new.tap do |_defaults|
      (self.class._defaults || {}).each do |name, value|
        _defaults[name] = value.is_a?(Proc) ? value.call(self) : value
      end
    end
  end

  def overrides
    return {} if @controller.nil?

    @_overrides ||= Hashie::Mash.new.tap do |_overrides|
      (controller(:params)[identifier] || {}).each do |name, value|
        _overrides[name] = value
      end
    end
  end

  def controller(variable_or_method_name)
    if @controller.instance_variable_defined?("@#{variable_or_method_name}")
      @controller.instance_variable_get("@#{variable_or_method_name}")
    elsif @controller.respond_to?(variable_or_method_name, true)
      @controller.send(variable_or_method_name)
    else
      nil
    end
  end

  def as_json
    { identifier => { "class" => self.class.name, "attributes" => attributes.as_json } }
  end

  private

  module ClassMethods
    attr_accessor :_attributes, :_defaults, :_template_name

    def attribute(name)
      self._attributes ||= []
      self._attributes << name
    end

    def attributes(*names)
      names.each { |name| attribute(name) }
    end

    def default(name, value)
      self._defaults ||= {}
      self._defaults[name] = value
    end

    def defaults(settings = {})
      settings.each { |name, value| default(name, value) }
    end

    def template_name(name)
      self._template_name = name.to_s
    end
  end

  class SourceMissing < StandardError; end
  class IdentifierMissing < StandardError; end
  class InvalidSetting < StandardError; end
end