require 'set'
require 'surrounded/context/role_map'
module Surrounded
  module Context
    def self.extended(base)
      base.send(:include, InstanceMethods)
      base.singleton_class.send(:alias_method, :setup, :initialize)
    end

    def triggers
      @triggers.dup
    end

    def policy
      @policy ||= :trigger
    end

    private

    def apply_roles_on(which)
      @policy = which
    end

    def initialize(*setup_args)
      private_attr_reader(*setup_args)

      # I want this to work so I can set the arity on initialize:
      # class_eval %Q<
      #   def initialize(#{*setup_args})
      #     arguments = parameters.map{|arg| eval(arg[1].to_s) }
      #     map_roles(setup_args.zip(arguments))
      #     apply_roles if policy == :initialize
      #   end
      # >

      define_method(:initialize){ |*args|
        map_roles(setup_args.zip(args))

        apply_roles if policy == :initialize
      }
    end

    def private_attr_reader(*method_names)
      attr_reader(*method_names)
      private(*method_names)
    end

    def trigger(name, *args, &block)
      store_trigger(name)

      define_method(:"trigger_#{name}", *args, &block)

      private :"trigger_#{name}"

      define_method(name, *args){
        begin
          apply_roles if policy == :trigger

          self.send("trigger_#{name}", *args)

        ensure
          remove_roles if policy == :trigger
        end
      }
    end

    def store_trigger(name)
      @triggers ||= Set.new
      @triggers << name
    end

    module InstanceMethods
      def role?(name, &block)
        return false unless role_map.role?(name)
        accessor = eval('self', block.binding)
        role_map.role_player?(accessor) && role_map.assigned_player(name)
      end

      def triggers
        self.class.triggers
      end

      private

      def role_map
        @role_map ||= RoleMap.new
      end

      def map_roles(role_object_array)
        role_object_array.each do |role, object|
          map_role(role, role_behavior_name(role), object)
        end
      end

      def map_role(role, mod_name, object)
        instance_variable_set("@#{role}", object)
        role_map.update(role, mod_name, object)
      end

      def policy
        @policy ||= self.class.policy
      end

      def add_interface(role, behavior, object)
        applicator = behavior.is_a?(Class) ? method(:add_class_interface) : method(:add_module_interface)

        role_player = applicator.call(object, behavior)
        map_role(role, role_module_basename(behavior), role_player)
        role_player.store_context(self)
        role_player
      end

      def add_module_interface(obj, mod)
        adder_name = module_extension_methods.find{|meth| obj.respond_to?(meth) }
        return obj if !adder_name

        obj.method(adder_name).call(mod)
        obj
      end

      def add_class_interface(obj, klass)
        wrapper_name = wrap_methods.find{|meth| klass.respond_to?(meth) }
        return obj if !wrapper_name

        klass.method(wrapper_name).call(obj)
      end

      def remove_interface(role, behavior, object)
        remover_name = (module_removal_methods + unwrap_methods).find{|meth| object.respond_to?(meth) }
        return object if !remover_name

        object.remove_context
        role_player = object.method(remover_name).call

        map_role(role, role_module_basename(behavior), role_player)

        role_player
      end

      def apply_roles
        traverse_map method(:add_interface)
      end

      def remove_roles
        traverse_map method(:remove_interface)
      end

      def traverse_map(applicator)
        role_map.each do |role, mod_name, object|
          if self.class.const_defined?(mod_name)
            applicator.call(role, self.class.const_get(mod_name), object)
          end
        end
      end

      def module_extension_methods
        [:cast_as, :extend]
      end

      def wrap_methods
        [:new]
      end

      def module_removal_methods
        [:uncast]
      end

      def unwrap_methods
        [:__getobj__]
      end

      def role_behavior_name(role)
        role.to_s.gsub(/(?:^|_)([a-z])/) { $1.upcase }.sub(/_\d+/,'')
      end

      def role_module_basename(mod)
        mod.to_s.split('::').last
      end
    end
  end
end