require 'set'
require 'surrounded/context/role_map'
require 'surrounded/access_control'
require 'surrounded/shortcuts'
require 'surrounded/east_oriented'

# Some features are only available in versions of Ruby
# where this method is true
unless defined?(module_method_rebinding?)
  def module_method_rebinding?
    return @__module_method_rebinding__ if defined?(@__module_method_rebinding__)
    sample_method = Enumerable.instance_method(:to_a)
    @__module_method_rebinding__ = begin
      !!sample_method.bind(Object.new)
    rescue TypeError
      false
    end
  end
end

# Extend your classes with Surrounded::Context to handle their
# initialization and application of behaviors to the role players
# passed into the constructor.
#
# The purpose of this module is to help you create context objects
# which encapsulate the interaction and behavior of objects inside.
module Surrounded
  module Context
    def self.extended(base)
      base.class_eval {
        @triggers = Set.new
        include InstanceMethods
      }
    end

    def new(*args, &block)
      instance = allocate
      instance.send(:preinitialize)
      instance.send(:initialize, *args, &block)
      instance.send(:postinitialize)
      instance
    end

    # Provides a Set of all available trigger methods where
    # behaviors will be applied to the roles before execution
    # and removed afterward.
    def triggers
      @triggers.dup
    end

    private

    # Set the default type of implementation for role methods for all contexts.
    def self.default_role_type
      @default_role_type ||= :module
    end

    class << self
      attr_writer :default_role_type
    end
    
    # Provide the ability to create access control methods for your triggers.
    def protect_triggers;  self.extend(::Surrounded::AccessControl); end
    
    # Automatically create class methods for each trigger method.
    def shortcut_triggers; self.extend(::Surrounded::Shortcuts); end
    
    # Automatically return the context object from trigger methods.
    def east_oriented_triggers; self.extend(::Surrounded::EastOriented); end

    def default_role_type
      @default_role_type ||= Surrounded::Context.default_role_type
    end

    # Set the default type of implementation for role method for an individual context.
    def default_role_type=(type)
      @default_role_type = type
    end

    # Set the time to apply roles to objects. Either :trigger or :initialize. 
    # Defaults to :trigger
    def apply_roles_on(which)
      @__apply_role_policy = which
    end

    def __apply_role_policy
      @__apply_role_policy ||= :trigger
    end

    # Shorthand for creating an instance level initialize method which
    # handles the mapping of the given arguments to their named role.
    def initialize(*setup_args)
      private_attr_reader(*setup_args)

      class_eval "
        def initialize(#{setup_args.join(',')})
          preinitialize
          arguments = method(__method__).parameters.map{|arg| eval(arg[1].to_s) }
          @role_map = RoleMap.new
          map_roles(#{setup_args}.zip(arguments))
          postinitialize
        end
      ", __FILE__, __LINE__
    end

    # Create a named behavior for a role using the standard library SimpleDelegator.
    def wrap(name, &block)
      require 'delegate'
      wrapper_name = name.to_s.gsub(/(?:^|_)([a-z])/){ $1.upcase }
      klass = private_const_set(wrapper_name, Class.new(SimpleDelegator, &block))
      klass.send(:include, Surrounded)
    end
    alias_method :wrapper, :wrap

    if module_method_rebinding?
      # Create an object which will bind methods to the role player
      def interface(name, &block)
        class_basename = name.to_s.gsub(/(?:^|_)([a-z])/){ $1.upcase }
        interface_name = class_basename + 'Interface'

        behavior = private_const_set(interface_name, Module.new(&block))

        require 'surrounded/context/negotiator'
        undef_method(name)
        define_method(name) do
          instance_variable_set("@#{name}", Negotiator.new(role_map.assigned_player(name), behavior))
        end
      end
    end

    # Define behaviors for your role players
    def role(name, type=nil, &block)
      role_type = type || default_role_type
      if role_type == :module
        mod_name = name.to_s.gsub(/(?:^|_)([a-z])/){ $1.upcase }
        private_const_set(mod_name, Module.new(&block))
      else
        meth = method(role_type)
        meth.call(name, &block)
      end
    rescue NameError => e
      raise e.extend(InvalidRoleType)
    end
    alias_method :role_methods, :role

    # Creates a context instance method which will apply behaviors to role players
    # before execution and remove the behaviors after execution.
    #
    # Alternatively you may define your own methods then declare them as triggers
    # afterward.
    # 
    # Example:
    #   trigger :some_event do
    #     # code here
    #   end
    #
    #   def some_event
    #     # code here
    #   end
    #   trigger :some_event
    #
    def trigger(*names, &block)
      if block.nil?
        names.each do |name|
          define_trigger_method(name, &block)
        end
      else
        name = names.first

        define_method(:"__trigger_#{name}", &block)

        private :"__trigger_#{name}"
        store_trigger(name)

        redo_method(name)
      end
    end

    def store_trigger(*names)
      @triggers.merge(names)
    end
    
    def define_trigger_method(name, &block)
      unless triggers.include?(name) || name.nil?
        alias_method :"__trigger_#{name}", :"#{name}"
        private :"__trigger_#{name}"
        remove_method :"#{name}"
        redo_method(name)
        store_trigger(name)
      end
    end

    def redo_method(name)
      class_eval %{
        def #{name}
          begin
            apply_roles if __apply_role_policy == :trigger

            #{trigger_return_content(name)}

          ensure
            remove_roles if __apply_role_policy == :trigger
          end
        end
      }, __FILE__, __LINE__
    end
    
    def trigger_return_content(name)
      %{self.send("__trigger_#{name}")}
    end
    
    # === Utility shortcuts
    
    # Set a named constant and make it private
    def private_const_set(name, const)
      unless self.const_defined?(name, false)
        const = const_set(name, const)
        private_constant name.to_sym
      end
      const
    end

    # Create attr_reader for the named methods and make them private
    def private_attr_reader(*method_names)
      attr_reader(*method_names)
      private(*method_names)
    end

    # Conditional const_get for a named role behavior
    def role_const(name)
      if const_defined?(name)
        const_get(name)
      end
    end

    module InstanceMethods
      # Check whether a given name is a role inside the context.
      # The provided block is used to evaluate whether or not the caller
      # is allowed to inquire about the roles.
      def role?(name, &block)
        return false unless role_map.role?(name)
        accessor = block.binding.eval('self')
        role_map.role_player?(accessor) && role_map.assigned_player(name)
      end

      # Check if a given object is a role player in the context.
      def role_player?(obj)
        role_map.role_player?(obj)
      end

      def triggers
        self.class.triggers
      end

      private

      def preinitialize
        @__apply_role_policy = self.class.send(:__apply_role_policy)
      end

      def postinitialize
        apply_roles if __apply_role_policy == :initialize
      end

      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 __apply_role_policy
        @__apply_role_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) if behavior
        role_player.send(: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.send(:remove_context) do; end
        role_player = object.method(remover_name).call

        map_role(role, role_module_basename(behavior), role_player) if behavior

        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 role_const_defined?(mod_name)
            applicator.call(role, role_const(mod_name), object)
          end
        end
      end

      # List of possible methods to use to add behavior to an object from a module.
      def module_extension_methods
        [:cast_as, :extend]
      end

      # List of possible methods to use to add behavior to an object from a wrapper.
      def wrap_methods
        [:new]
      end

      # List of possible methods to use to remove behavior from an object with a module.
      def module_removal_methods
        [:uncast]
      end

      # List of possible methods to use to remove behavior from an object with a wrapper.
      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

      def role_const(name)
        self.class.send(:role_const, name)
      end

      def role_const_defined?(name)
        self.class.const_defined?(name)
      end
    end
  end
end