require 'set'

Module.class_eval do
  def alias name = nil
    if name
      name.must_be.a String
      name.must_not_be.blank
      @alias = name.to_s
    else
      @alias ||= self.name.split('::').last
    end
  end

  def is?(base)
    ancestors.include?(base)
  end

  def namespace
    if @module_namespace_defined
      @module_namespace
    else
      @module_namespace_defined = true
      @module_namespace = Module.namespace_for name
    end
  end

  def each_namespace &block
    current = namespace
    while current do
      block.call current
      current = current.namespace
    end
  end

  def each_ancestor include_standard = false, &block
    if include_standard
      ancestors.each{|a| block.call a unless a == self}
    else
      exclude = [self, Object, Kernel]
      ancestors.each do |a|
        block.call a unless exclude.include? a
      end
    end
  end

  def self_ancestors_and_namespaces &b
    b.call self
    each_ancestor &b
    each_namespace &b
  end
  
  # TODO cache it?
  def self.namespace_for class_name    
    list = class_name.split("::")
    if list.size > 1
      list.pop
      return eval(list.join("::"), TOPLEVEL_BINDING, __FILE__, __LINE__)
    else
      return nil
    end
  end

  def inheritable_accessor attribute_name, default_value
    raise "Can be used only for Class and Module" unless self.class.is? Module

    iv_name = "@#{attribute_name}"
    iv_defined = "@#{attribute_name}_defined"

    define_method attribute_name do
      unless instance_variable_get(iv_defined)
        iv = nil
        ancestors[1..-1].each do |a|
          if a.respond_to?(attribute_name) and (value = a.send(attribute_name))
            iv = value.deep_clone
            break
          end
        end
        iv ||= default_value.deep_clone
        instance_variable_set iv_name, iv
        instance_variable_set iv_defined, true
        iv
      else
        instance_variable_get iv_name
      end
    end

    define_method "#{attribute_name}=" do |value|
      instance_variable_set iv_name, value
      instance_variable_set iv_defined, true
    end
  end

  raise "Internal error, it shouldn't be loaded twice!" if defined? ESCAPE_METHOD_SYMBOLS # some tricky error when runing spec with rake
  ESCAPE_METHOD_SYMBOLS = [
    ['==', 'assign'],
    ['>', 'gt'],
    ['<', 'lt'],
    ['>=', 'gte'],
    ['<=', 'lte'],
    ['?', 'qst'],
    ['!', 'imp'],
    ['<=>', 'lorg'],
    ['*', 'mp'],
    ['+', 'add'],
    ['-', 'sub'],
    ['=', 'assign'],
    ['**', 'pw'],
    ['=~', 'sim'],
    ['[]', 'sb'],
  ]

  def escape_method method
    m = method.to_s.clone
    ESCAPE_METHOD_SYMBOLS.each{|from, to| m.gsub! from, to}
    raise "Invalid method name '#{method}'!" unless m =~ /^[_a-zA-Z0-9]+$/
    m.to_sym
  end

  def attr_required *attrs
    attrs.each do |attr|
      define_method(attr){instance_variable_get(:"@#{attr}") || raise("attribute :#{attr} not defined!")}
    end
  end

  public :include, :define_method


  # copied from rails
  def delegate(*methods)
    options = methods.pop
    unless options.is_a?(Hash) && to = options[:to]
      raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)."
    end

    if options[:prefix] == true && options[:to].to_s =~ /^[^a-z_]/
      raise ArgumentError, "Can only automatically set the delegation prefix when delegating to a method."
    end

    prefix = options[:prefix] && "#{options[:prefix] == true ? to : options[:prefix]}_" || ''

    file, line = caller.first.split(':', 2)
    line = line.to_i

    methods.each do |method|
      on_nil =
        if options[:allow_nil]
          'return'
        else
          %(raise "#{self}##{prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}")
        end

      module_eval(<<-EOS, file, line - 5)
        if instance_methods(false).map(&:to_s).include?("#{prefix}#{method}")
          remove_possible_method("#{prefix}#{method}")
        end

        def #{prefix}#{method}(*args, &block)               # def customer_name(*args, &block)
          #{to}.__send__(#{method.inspect}, *args, &block)  #   client.__send__(:name, *args, &block)
        rescue NoMethodError                                # rescue NoMethodError
          if #{to}.nil?                                     #   if client.nil?
            #{on_nil}                                       #     return # depends on :allow_nil
          else                                              #   else
            raise                                           #     raise
          end                                               #   end
        end                                                 # end
      EOS
    end
  end
end