{-# LANGUAGE TypeFamilies, MultiParamTypeClasses, GADTs, FlexibleInstances, ScopedTypeVariables, DeriveDataTypeable, TypeSynonymInstances, StandaloneDeriving, NamedFieldPuns #-}

{-|
This module defines a simple 'Neuron' which just fails (throws a 'DissolvingException') in 'grow'ing phase. It can be used to test
error recovery and cleanup in 'grow'ing phase or early stages of 'live'ing phase in other 'Neuron's by using something like:

> _ <- growNeuron defaultOptions :: NerveNone FailNeuron

somewhere among (or after) 'growNeuron' calls for other 'Neuron's in 'Incubation'.
-}

module Control.Etage.Fail (
  FailNeuron,
  FailFromImpulse,
  FailForImpulse,
  FailOptions,
  NeuronFromImpulse,
  NeuronForImpulse,
  NeuronOptions
) where

import Data.Typeable

import Control.Etage

data FailNeuron deriving (Typeable)

instance Show FailNeuron where
  show = show . typeOf

-- | 'Impulse's from 'FailNeuron'. This 'Neuron' does not define any 'Impulse's it would send.
type FailFromImpulse = NeuronFromImpulse FailNeuron
-- | 'Impulse's for 'FailNeuron'. This 'Neuron' does not define any 'Impulse's it would receive.
type FailForImpulse = NeuronForImpulse FailNeuron
-- | Options for 'FailNeuron'. This 'Neuron' does not define any options.
type FailOptions = NeuronOptions FailNeuron

-- | Impulse instance for 'FailNeuron'.
instance Impulse FailFromImpulse where
  impulseTime _ = undefined
  impulseValue _ = undefined

-- | Impulse instance for 'FailNeuron'.
instance Impulse FailForImpulse where
  impulseTime _ = undefined
  impulseValue _ = undefined

deriving instance Show FailFromImpulse
deriving instance Show FailForImpulse

-- | A simple 'Neuron' which just fails in 'grow'ing phase.
instance Neuron FailNeuron where
  data NeuronFromImpulse FailNeuron
  data NeuronForImpulse FailNeuron
  data NeuronOptions FailNeuron
  
  grow _ = dissolving (undefined :: FailNeuron)