# encoding: UTF-8
module Maintain
  class Maintainer
    attr_reader :back_end

    def aggregate(name, options)
      if options.is_a?(Hash) && options.has_key?(:as)
        options = options[:as]
      end
      aggregates[name] = options
      # Now we're going to add proxies to test for state being in this aggregate. Don't create
      # this method unless it doesn't exist.
      boolean_method = "#{name}?"
      if method_free?(boolean_method)
        # Define it if'n it don't already exit! These are just proxies - so Foo.maintains(:state) { state :awesome }
        # will now have Foo.new.awesome?. But that's really just a proxy for Foo.new.state.awesome?
        # So they're just shortcuts for brevity's sake.
        maintainee.class_eval <<-EOC
          def #{boolean_method}
            #{@attribute}.#{boolean_method}
          end
        EOC
      end
      # Now define the state
      if back_end && method_free?(name, true)
        back_end.aggregate(maintainee, name, @attribute, options.map{|value| states[value][:value].is_a?(Symbol) ? states[value][:value].to_s : states[value][:value] })
      end
    end

    def aggregates
      @aggregates ||= {}
    end

    def bitmask(value)
      @bitmask = !!value
    end

    def bitmask?
      !!@bitmask
    end

    def default(state = nil)
      if state
        if bitmask?
          @default = (@default || 0) | states[state][:value]
        else
          @default = state
        end
      else
        @default
      end
    end

    def default?
      !!@default
    end

    def hook(event, state, instance)
      if state && state.to_s.strip != '' && hooks[state.to_sym] && hook_definitions = hooks[state.to_sym][event.to_sym]
        hook_definitions.each do |hook_definition|
          next if hook_definition[:if] && !call_method_or_proc_on_instance(hook_definition[:if], instance)
          next if hook_definition[:unless] && call_method_or_proc_on_instance(hook_definition[:unless], instance)
          call_method_or_proc_on_instance(hook_definition[:method], instance)
        end
      end
    end

    def initialize(maintainee, attribute, options = {})
      @maintainee = maintainee.name
      @attribute = attribute.to_sym
      if back_end = options.delete(:back_end)
        @back_end = Maintain::Backend.build(back_end)
      end
      options.each do |key, value|
        self.send(key, value)
      end
    end

    def integer(value)
      @integer = !!value
    end

    def integer?
      !!@integer
    end

    def on(*args, &block)
      options = args.last.is_a?(Hash) ? args.pop : {}
      event, state = args.shift, args.shift
      method = args.shift
      if block_given?
        method = block
      end
      if back_end && back_end.respond_to?(:on)
        back_end.on(maintainee, @attribute, event, state, method, options)
      else
        hooks[state.to_sym] ||= {}
        hooks[state.to_sym][event.to_sym] ||= []
        method_hash = {:method => method}.merge(options)
        if old_definition = hooks[state.to_sym][event.to_sym].find{|hook| hook[:method] == method}
          old_definition.merge!(method_hash)
        else
          hooks[state.to_sym][event.to_sym].push(method_hash)
        end
      end
    end

    def state_name_for(value)
      if value = states.find {|key, options| options[:compare_value] == value}
        value[0]
      end
    end

    def state(name, value = nil, options = {})
      if value.is_a?(Hash)
        options = value
        value = nil
      end
      @increment ||= 0
      if bitmask?
        unless value.is_a?(Integer)
          value = @increment
        end
        value = 2 ** value.to_i
      elsif value.is_a?(Integer)
        integer(true)
      end
      value ||= name
      states[name] = {:compare_value => !bitmask? && value.is_a?(Integer) ? value : @increment, :value => value}
      @increment += 1
      if !maintainee.respond_to?(name) && back_end
        back_end.state maintainee, name, @attribute, value.is_a?(Symbol) ? value.to_s : value
      end

      # We need the states hash to contain the compare_value for this guy before we can set defaults on the bitmask,
      # since the default should actually be a bitmask of all possible default states
      if options.has_key?(:default)
        default(name)
      end

      if options.has_key?(:enter)
        on :enter, name.to_sym, options.delete(:enter)
      end

      if options.has_key?(:exit)
        on :exit, name.to_sym, options.delete(:exit)
      end

      # Now we're going to add proxies to test for state. These methods only get added if a
      # method of their name doesn't already exist.
      boolean_method = "#{name}?"
      # Override any attribute_state? methods, because those we need for hooks...
      maintainee.class_eval <<-EOC
        def #{@attribute}_#{boolean_method}
          #{@attribute}.#{boolean_method}
        end
        #{"alias :#{boolean_method} :#{@attribute}_#{boolean_method}" if method_free?(boolean_method)}
      EOC
    end

    def states
      @states ||= {}
    end

    def value(instance, initial = nil)
      initial = (back_end && back_end.read(instance, @attribute)) || initial || @default
      if bitmask?
        BitmaskValue.new(self, initial || 0)
      elsif integer?
        IntegerValue.new(self, initial)
      else
        Value.new(self, initial)
      end
    end

    protected
    def hooks
      @hooks ||= {}
    end

    def maintainee
      @maintainee.split('::').inject(Object) {|mod, const| mod.const_get(const) }
    end

    def method_free?(method_name, class_method = false)
      # Ugly hack so we don't fetch it 100 times for no reason
      maintainee_class = maintainee
      if class_method
        respond_to = maintainee_class.respond_to?(method_name)
        methods = maintainee_class.public_methods + maintainee_class.private_methods + maintainee_class.protected_methods
      else
        respond_to = false
        methods = maintainee_class.instance_methods
        # methods = %w(instance_methods public_instance_methods private_instance_methods protected_instance_methods).inject([]) do |methods, method|
        #   methods + maintainee_class.send(method)
        # end.uniq
      end
      # Ruby 1.8 returns arrays of strings; ruby 1.9 returns arrays of symbols. "Awesome."
      !respond_to && !methods.include?(method_name) && !methods.include?(method_name.to_sym)
    end

    def method_missing(method, *args)
      if states.has_key?(method)
        states[method][:value]
      else
        super
      end
    end

    private
    def call_method_or_proc_on_instance(method, instance)
      if method.is_a?(Proc)
        instance.instance_eval(&method)
      else
        instance.send(method)
      end
    end
  end
end