defmodule Scopes.CSys.Program do
  require Logger

  alias Scopes.CSys
  alias Scopes.CSys.Environ
  alias Scopes.Shape

  defmodule State do
    defstruct [:value, :count, :stage, :prog]
  end

  def prepare(prog, args) do
    state = %State{
      value: args[:bias], 
      count: 0,
      stage: :initial, 
      prog: prog
    }
    {state, get_proc(state)}
  end

  def get_proc(state) do
    get_proc(elem(state.prog, 0), state.stage)
  end

  defp get_proc(stages, stage) do
    stages[stage] || stages[:default]
  end

  # basic program

  def basic_prog(args) do
    default = basic_active(args)
    stages = %{
      default: default,
      initial: basic_initial(args),
      active: default,
      retired: default
    }
    transitions = %{
      restart: :initial,
      retire: :retired,
      next:  [initial: :active, active: :retired]
    }
    {stages, transitions}
  end

  def prepare_basic(args \\ [threshold: 0, bias: 0]) do
    prepare(basic_prog(args), args)
  end

  # basic processors
  
  def basic_initial(args) do
    basic(args)
  end

  def basic_active(args) do
    basic(args)
  end

  #def basic(msg, scope) do  # + proc_ops
  def basic(args) do  # + proc_ops
    fn msg, scope ->
      case Shape.head(msg) do
        [:csys, :data | _rest] -> process_data(msg, scope, args)
        #[:csys, :trigger | _rest] -> process_trigger(msg, scope)
        [:csys, :set | _rest] -> set(msg, scope)
        [:csys, :connect | _rest] -> CSys.connect(msg, scope)
        [:csys, :create, :succ | _rest] -> create_succ(msg, scope)
        [:csys, :create, :pred | _rest] -> create_pred(msg, scope)
        #[:csys, :next | _rest] -> next(scope, meta)
        #[:csys, action | rest] -> transition(action, scope)
        _ -> CSys.forward(msg, scope) || CSys.notify(msg, scope)
      end
    end
  end

  # message handlers // proc steps

  def process_value(_msg, _scope, _ops) do
    #proc ops: 
    #reduce, (&(&1 + &2))
    #trigger_cond,  (&(&1 > 0))
    #out_op, (&(&1)) # (&(rem(&1 - 1, 5) + 1)
    #output (&forward_or_notify)
    #next_op, (const(0)) # (&max(&1 - 5, 0))
  end

  def process_data(msg, scope, args) do
    data = Shape.data(msg)
    state = CSys.state(scope)
    value_n = state.value + data.value
    threshold = args[:threshold] || 0
    bias = args[:bias] || 0
    Logger.info data: data.value, state: state.value, threshold: threshold
    if value_n >= threshold do
      msg = Shape.create(Shape.head(msg), data: %{data | value: value_n})
      CSys.forward(msg, scope) || CSys.notify(msg, scope)
      state_n = if bias, do: %{state | value: bias}, else: state
      CSys.update(put_elem(scope, 0, state_n))
    else
      state_n = %{state | value: value_n}
      CSys.update(put_elem(scope, 0, state_n))
    end
  end

  def set(msg, scope) do
    data = Shape.data(msg)
    state = CSys.state(scope)
    value = data[:value] || state.value
    threshold = data[:threshold] || state.threshold
    bias = data[:bias] || state.bias
    state_n = %{state | value: value, threshold: threshold, bias: bias}
    CSys.update(put_elem(scope, 0, state_n))
  end

  def create_succ(msg, scope) do
    new = CSys.create(msg, restart(scope))
    data = Shape.data(msg)
    CSys.send_message(self(), ~w(csys connect)a, Map.put(data, :target, new))
  end

  def create_pred(msg, scope) do
    new = CSys.create(msg, restart(scope))
    data = Shape.data(msg)
    CSys.send_message(new, ~w(csys connect)a, Map.put(data, :target, self()))
  end

  # synapse operations

  def multiply(n) do
    fn msg ->
      value = Shape.data(msg)[:value] || 0
      Shape.create(Shape.head(msg), data: %{Shape.data(msg) | value: n * value})
    end
  end

  def negate(), do: multiply(-1)

  # helper functions

  def restart({state, _proc, syns, env}) do
    state_n = %{state | stage: :initial}
    {state_n, get_proc(state_n), syns, env}
  end

  # demo init sequences
 
  def init_seq_b1() do 
    zero = [:csys, :c00, {0, 0}]
    one = [:csys, :s01, {1, 0}]
    two = [:csys, :c00, {1, 1}]
    three = [:csys, :s01, {1, 1}]
    [
      fn state -> 
        Environ.send_message(state, zero, ~w(csys create pred)a, 
         %{op: [CSys.data_only(), negate()], addr: one})
     end,
     fn state -> 
       Environ.send_message(state, one, ~w(csys create succ)a, 
         %{op: CSys.data_only(), addr: two}) 
     end,
      fn state -> 
        Environ.send_message(state, two, ~w(csys create pred)a, %{addr: three}) 
      end,
      fn state -> Environ.connect(state, three, zero) end
    ]
  end

  def init_recursive_1() do 
    zero = [:csys, :c00, {0, 0}]
    [
      fn state -> 
        Environ.connect(state, zero, zero, negate())
        Environ.send_message(state, zero, ~w(csys create succ)a, 
          %{addr: [:csys, :e01, {1, 1}]})
      end,
      fn state ->
        Environ.send_message(state, zero, ~w(csys create pred)a,
          %{addr: [:csys, :s01, {1, 1}]})
      end
    ]
  end
end