# ---
# Excerpted from "Programming Elixir ≥ 1.6",
# published by The Pragmatic Bookshelf.
# Copyrights apply to this code. It may not be used to create training material,
# courses, books, articles, and the like. Contact us if you are in doubt.
# We make no guarantees that this code is fit for any purpose.
# Visit http://www.pragmaticprogrammer.com/titles/elixir16 for more book information.
# ---
defmodule NOP.Element.FBE do

  defmacro __using__([]) do
    quote do
      use GenServer
      use NOP.Element.ElementBase

      require Logger

      def start_link(fbe_name) do

        state = init_state(fbe_name)

        state = reset_statistics_to_state(state)

        state = set_name(state, fbe_name)

        #GenServer.start_link(__MODULE__, state, name: String.to_atom(fbe_name))
        GenServer.start_link(__MODULE__, state)
      end

      def init(state) do
        {:ok, state}
      end

      def handle_call({:get_attr, attr_name}, _from, state) do
        {:reply, get_attribute(get_attributes_from_state(state), attr_name), state}
      end

      def handle_call(:get_name, _from, state) do
        {:reply, get_name(state), state}
      end

      def handle_cast({:set_attr, attr_name, attr_value}, state) do

        fbe_attrs = get_attributes_from_state(state)

        fbe_attrs = set_attribute(fbe_attrs, attr_name, attr_value, state)

        #beg_time = get_timestamp()

        #state = set_attributes_to_state(state, fbe_attrs)

        # end_time = get_timestamp()

        #state = add_statistics_to_state(state, diff_between_timestamp(beg_time,end_time))

        {run_time, state} = :timer.tc(
          fn  ->
            set_attributes_to_state(state, fbe_attrs)
          end
        )

        state = add_statistics_to_state(state, run_time)

        {:noreply, state}
      end

      def handle_cast({:link_premise, attr_name, premise, side, premise_name}, state) do
        state = link_premise_to_attribute(state, attr_name, premise, side, premise_name)
        {:noreply, state}
      end

      defp init_state(fbe_name) do
        # int_attributes needs to be defined!
        fbe_attrs = int_attributes()

        %{:attributes => fbe_attrs, :links => %{}}
      end

      defp get_attributes_from_state(state) do
        Map.get(state, :attributes)
      end

      defp set_attributes_to_state(state, fbe_attrs) do
        Map.put(state, :attributes, fbe_attrs)
      end

      defp get_attribute(fbe_attrs, attr_name) do
        Map.get(fbe_attrs, attr_name)
      end

      defp notify_premises_int([], _, _, _) do
        # No premises to notify
      end

      defp notify_premises_int(nil, _, _, _) do
        # No premises to notify
      end

      defp notify_premises_int([{premise, side} | premises], attr_name, attr_value, fbe_name) do
        GenServer.cast(premise, {:notify, side, self(), attr_name, attr_value, fbe_name})

        notify_premises_int(premises, attr_name, attr_value, fbe_name)
      end

      defp notify_premises(state, attr_name, attr_value, fbe_name) do
        links = get_links(state)

        premises = Map.get(links, attr_name)

        notify_premises_int(premises, attr_name, attr_value, fbe_name)
      end

      defp set_attribute(fbe_attrs, attr_name, attr_value, state) do
        # Get Old Value
        old_value = get_attribute(fbe_attrs, attr_name)

        if old_value != attr_value do
          # Get Name
          fbe_name = get_name(state)

          Logger.debug(
            "FBE attribute #{fbe_name}.#{attr_name} changed from #{old_value} to #{attr_value}"
          )

          notify_premises(state, attr_name, attr_value, fbe_name)

          Map.put(fbe_attrs, attr_name, attr_value)
        else
          fbe_attrs
        end
      end

      defp get_links(state) do
        Map.get(state, :links)
      end

      defp set_links(state, links) do
        Map.put(state, :links, links)
      end

      defp link_premise_to_attribute(state, attr_name, premise, side, premise_name) do
        Logger.debug(
          "FBE attribute #{get_name(state)}.#{attr_name} linked to premise #{premise_name} on #{
            side
          } side"
        )

        links = get_links(state)

        premises = Map.get(links, attr_name)

        premises =
          if premises == nil do
            []
          else
            premises
          end

        premises = premises ++ [{premise, side}]

        links = Map.put(links, attr_name, premises)

        set_links(state, links)
      end
    end
  end
end