require 'metaclass'

module Mocha

  class ClassMethod

    PrependedModule = Class.new(Module)

    attr_reader :stubbee, :method

    def initialize(stubbee, method)
      @stubbee = stubbee
      @original_method, @original_visibility = nil, nil
      @method = RUBY_VERSION < '1.9' ? method.to_s : method.to_sym
    end

    def stub
      hide_original_method
      define_new_method
    end

    def unstub
      remove_new_method
      restore_original_method
      mock.unstub(method.to_sym)
      unless mock.any_expectations?
        reset_mocha
      end
    end

    def mock
      stubbee.mocha
    end

    def reset_mocha
      stubbee.reset_mocha
    end

    def hide_original_method
      if method_exists?(method)
        begin
          @original_method = stubbee._method(method)
          @original_visibility = :public
          if stubbee.__metaclass__.protected_instance_methods.include?(method)
            @original_visibility = :protected
          elsif stubbee.__metaclass__.private_instance_methods.include?(method)
            @original_visibility = :private
          end
          if @original_method && @original_method.owner == stubbee.__metaclass__
            stubbee.__metaclass__.send(:remove_method, method)
          end

          include_prepended_module if RUBY_VERSION >= '2.0'
        rescue NameError
          # deal with nasties like ActiveRecord::Associations::AssociationProxy
        end
      end
    end

    def define_new_method
      definition_target.class_eval(<<-CODE, __FILE__, __LINE__ + 1)
        def #{method}(*args, &block)
          mocha.method_missing(:#{method}, *args, &block)
        end
      CODE
      if @original_visibility
        Module.instance_method(@original_visibility).bind(definition_target).call(method)
      end
    end

    def remove_new_method
      definition_target.send(:remove_method, method)
    end

    def restore_original_method
      if @original_method && @original_method.owner == stubbee.__metaclass__
        if RUBY_VERSION < '1.9'
          original_method = @original_method
          stubbee.__metaclass__.send(:define_method, method) do |*args, &block|
            original_method.call(*args, &block)
          end
        else
          stubbee.__metaclass__.send(:define_method, method, @original_method)
        end
      end
      if @original_visibility
        Module.instance_method(@original_visibility).bind(stubbee.__metaclass__).call(method)
      end
    end

    def matches?(other)
      return false unless (other.class == self.class)
      (stubbee.object_id == other.stubbee.object_id) and (method == other.method)
    end

    alias_method :==, :eql?

    def to_s
      "#{stubbee}.#{method}"
    end

    def method_exists?(method)
      symbol = method.to_sym
      __metaclass__ = stubbee.__metaclass__
      __metaclass__.public_method_defined?(symbol) || __metaclass__.protected_method_defined?(symbol) || __metaclass__.private_method_defined?(symbol)
    end

    private

    def include_prepended_module
      possible_prepended_modules = stubbee.__metaclass__.ancestors.take_while do |mod|
        !(Class === mod)
      end

      if possible_prepended_modules.any?
        @definition_target = PrependedModule.new
        stubbee.__metaclass__.__send__ :prepend, @definition_target
      end
    end

    def definition_target
      @definition_target ||= stubbee.__metaclass__
    end

  end

end