require 'active_support/core_ext/hash/indifferent_access'

module Traitorous

  # Use the HashWithIndifferentAccess from the activesupport gem.
  HASH = HashWithIndifferentAccess

  # Read the VERSION file in gem root to set version number.
  VERSION = File.read('VERSION')

  # The converter namespace is used to store Converter classes.
  # Each Converter may take initializer arguments,  to allow specific classes or
  # values to be defined, and 2 methods: :do_import and :do_export.
  # do_import is meant to take the data, and use the initial data to combine to
  # build objects or other data structures.
  module Converter
    # The purpose of the converters are to facilitate the importation of simple
    #   JSON or YAML data and import that data into an arbitrarily nested tree
    #   of objects.  And then to take those object and be able to export that data
    #   in a simple form ready to save.
    #   opts = {some: 'deep', data: ['structures']}
    #    r = Mission.new(opts)
    #    Mission.new(r.export) == r
    require 'traitorous/converter/identity'
    require 'traitorous/converter/default_value_static'
    require 'traitorous/converter/model'
    require 'traitorous/converter/uniform_array'
    require 'traitorous/converter/method_keyed_uniform_hash'
    # if no other converter is declared, use the identity converter which
    # merely pass through the data passed to it.
    DEFAULT_CONVERTER = Converter::Identity.new
  end

  require 'traitorous/equality'

  module ClassMethods
    attr_accessor :traits

    def trait(attr_name, converter = Traitorous::Converter::DEFAULT_CONVERTER)
      self.traits            ||= HASH.new
      # sub hash used here, {} chosen for expansion possibility, but only
      #   :converter is in use
      self.traits[attr_name] = {converter: converter}
      attr_accessor attr_name
    end
  end

  def self.included(base)
    base.extend(ClassMethods)
  end

  def initialize(opts = {})
    raise "No traits have been defined for #{self.class}" unless self.class.traits
    @opts = HASH.new(opts)
    traits.each_pair do |new_trait, trait_opts|
      converter = trait_opts[:converter]
      val = converter.do_import(@opts.fetch(new_trait, nil))
      self.send("#{new_trait}=".intern, val)
    end
  end

  def export
    exported = HASH.new
    traits.each_pair do |trait_name, trait_opts|
      attr_value = self.public_send(trait_name.intern)
      exported[trait_name] = trait_opts[:converter].do_export(attr_value)
    end
    exported
  end

  def traits
    self.class.traits
  end

  def inspect
    string = "#<#{self.class.name}:#{self.object_id} "
    fields = self.class.traits.keys.map{|field| "#{field}: #{self.send(field).inspect}"}
    string << fields.join(", ") << ">"
  end

end