# Preferable allows defining preference accessor methods.
#
# A class including Preferable must implement #preferences which should return
# an object responding to .fetch(key), []=(key, val), and .delete(key).
#
# The generated writer method performs typecasting before assignment into the
# preferences object.
#
# Examples:
#
#   # Spree::Base includes Preferable and defines preferences as a serialized
#   # column.
#   class Settings < Spree::Base
#     preference :color,       :string,  default: 'red'
#     preference :temperature, :integer, default: 21
#   end
#
#   s = Settings.new
#   s.preferred_color # => 'red'
#   s.preferred_temperature # => 21
#
#   s.preferred_color = 'blue'
#   s.preferred_color # => 'blue'
#
#   # Typecasting is performed on assignment
#   s.preferred_temperature = '24'
#   s.preferred_color # => 24
#
#   # Modifications have been made to the .preferences hash
#   s.preferences #=> {color: 'blue', temperature: 24}
#
#   # Save the changes. All handled by activerecord
#   s.save!
module Spree::Preferences::Preferable
  extend ActiveSupport::Concern

  included do
    extend Spree::Preferences::PreferableClassMethods
  end

  # Get a preference
  # @param name [#to_sym] name of preference
  # @return [Object] The value of preference +name+
  def get_preference(name)
    has_preference! name
    send self.class.preference_getter_method(name)
  end

  # Set a preference
  # @param name [#to_sym] name of preference
  # @param value [Object] new value for preference +name+
  def set_preference(name, value)
    has_preference! name
    send self.class.preference_setter_method(name), value
  end

  # @param name [#to_sym] name of preference
  # @return [Symbol] The type of preference +name+
  def preference_type(name)
    has_preference! name
    send self.class.preference_type_getter_method(name)
  end

  # @param name [#to_sym] name of preference
  # @return [Object] The default for preference +name+
  def preference_default(name)
    has_preference! name
    send self.class.preference_default_getter_method(name)
  end

  # Raises an exception if the +name+ preference is not defined on this class
  # @param name [#to_sym] name of preference
  def has_preference!(name)
    raise NoMethodError.new "#{name} preference not defined" unless has_preference? name
  end

  # @param name [#to_sym] name of preference
  # @return [Boolean] if preference exists on this class
  def has_preference?(name)
    defined_preferences.include?(name.to_sym)
  end

  # @return [Array<Symbol>] All preferences defined on this class
  def defined_preferences
    self.class.defined_preferences
  end

  # @return [Hash{Symbol => Object}] Default for all preferences defined on this class
  def default_preferences
    Hash[
      defined_preferences.map do |preference|
        [preference, preference_default(preference)]
      end
    ]
  end

  private

  def convert_preference_value(value, type)
    return nil if value.nil?
    case type
    when :string, :text
      value.to_s
    when :password
      value.to_s
    when :decimal
      BigDecimal.new(value.to_s)
    when :integer
      value.to_i
    when :boolean
      if !value ||
         value == 0 ||
         value =~ /\A(f|false|0)\Z/i ||
         (value.respond_to?(:empty?) && value.empty?)
         false
      else
         true
      end
    when :array
      raise TypeError, "Array expected got #{value.inspect}" unless value.is_a?(Array)
      value
    when :hash
      raise TypeError, "Hash expected got #{value.inspect}" unless value.is_a?(Hash)
      value
    else
      value
    end
  end
end