module Cuboid

# @author Tasos "Zapotek" Laskos <tasos.laskos@gmail.com>
class OptionGroup

    # @author Tasos "Zapotek" Laskos <tasos.laskos@gmail.com>
    class Error < Options::Error
    end

    class <<self

        # @return   [Hash]
        #   Specified default values for attribute readers.
        def defaults
            @defaults ||= {}
        end

        # Sets default values for attribute readers, when an attribute reader
        # returns `nil` the default values will be returned instead.
        #
        # @param    [Hash]  default_values
        #   Default values for attributes.
        def set_defaults( default_values )
            defaults.merge! default_values

            # Set the specified default values as overrides to the attribute
            # readers.
            defaults.each do |ivar, value|
                define_method "#{ivar}=" do |v|
                    instance_variable_set( "@#{ivar}".to_sym, v.nil? ? value : v)
                end
            end

            defaults
        end

        def inherited( child )
            Options.register_group child
        end
    end

    def initialize
        defaults.each do |k, v|
            send "#{k}=", v
        end
    end

    def to_rpc_data
        to_h.my_stringify_keys(false)
    end

    # @return   [Hash]
    #   Values for all attribute accessors which aren't the defaults.
    def to_h
        h = {}
        instance_variables.each do |ivar|
            method = normalize_ivar( ivar )
            sym    = method.to_sym
            value  = instance_variable_get( ivar )

            next if !respond_to?( "#{method}=" )

            h[sym] = value
        end
        h
    end
    def to_hash
        to_h
    end

    # @return   [Hash]
    #   Hash of errors with the name of the invalid options as the keys.
    #
    # @abstract
    def validate
        {}
    end

    def ==( other )
        hash == other.hash
    end

    def hash
        to_h.hash
    end

    # @param    [Hash]  options
    #   Data to use to update the group's attributes.
    #
    # @return   [OptionGroup]
    #   `self`
    def update( options )
        options.to_hash.each { |k, v| send( "#{k}=", v ) }
        self
    end

    # @param    [OptionGroup]  other
    #
    # @return   [OptionGroup]
    #   `self`
    def merge( other )
        update( other.to_h )
    end

    # @return   (see .defaults)
    def defaults
        self.class.defaults
    end

    def self.attr_accessor( *vars )
        attributes.concat( vars )
        super( *vars )
    end

    def self.attributes
        @attributes ||= []
    end

    def attributes
        self.class.attributes
    end

    private

    def normalize_ivar( ivar )
        ivar.to_s.gsub( '@', '' )
    end
end
end