defmodule Scopes.CSys.Program do
  import Scopes.CSys, only: [
    neuron: 1, update_neuron: 1, synapse: 3, 
    syns: 1, env: 1
  ]

  alias Scopes.Core.Actor

  # programs

  def basic_prog() do
    default = &basic_active/2
    %{default: default,
      initial: default,
      active: default,
      retired: default
    }
  end

  # processors

  def basic_active(msg = {head, _info}, scope) do
    case head do
      [:csys, :create, :pred | _rest] -> create_pred(scope)
      [:csys, :create, :succ | _rest] -> create_succ(scope)
      #[:csys, :next | _rest] -> CSys.update_neuron({state, &basic_active/2, syns, env})
      #[:csys, :next | _rest] -> next(:active, scope)
      _ -> forward(msg, scope) || notify(msg, scope)
    end
  end

  def basic_active(msg, scope) do
    forward(msg, scope) || notify(msg, scope)
  end

# processor steps

  def notify(msg, scope) do
    Actor.send(env(scope), msg)
  end

  def forward(msg, scope) do
    Enum.reduce(syns(scope), false, fn s, _acc -> s.(msg); true end)
  end

# step functions

# create_... steps
# todo: provide parameters for initial state, proc / stage, op,
#       depending on state and stage (proc) of self, as well as message, env, ...

  def create_pred(scope = {_state, proc, _syns, env}) do
    syn = synapse(self(), &Function.identity/1, 0)
    new = neuron({[], proc, [syn], env})
    notify({:created, new}, scope)
  end

  def create_succ (scope = {state, proc, syns, env}) do
    new = neuron({[], proc, [], env})
    syn = synapse(new, &Function.identity/1, 0)
    update_neuron({state, proc, [syn | syns], env})
    notify({:created, new}, scope)
  end
end