-- |
-- Module     : Simulation.Aivika.Activity
-- Copyright  : Copyright (c) 2009-2014, David Sorokin <david.sorokin@gmail.com>
-- License    : BSD3
-- Maintainer : David Sorokin <david.sorokin@gmail.com>
-- Stability  : experimental
-- Tested with: GHC 7.8.3
--
-- It models an activity that can be utilised. The activity is similar to a 'Server'
-- but destined for simulation within 'Net' computation.
module Simulation.Aivika.Activity
       (-- * Activity
        Activity,
        newActivity,
        newStateActivity,
        -- * Processing
        activityNet,
        -- * Activity Properties
        activityInitState,
        activityState,
        activityTotalUtilisationTime,
        activityTotalIdleTime,
        activityUtilisationTime,
        activityIdleTime,
        activityUtilisationFactor,
        activityIdleFactor,
        -- * Summary
        activitySummary,
        -- * Derived Signals for Properties
        activityStateChanged,
        activityStateChanged_,
        activityTotalUtilisationTimeChanged,
        activityTotalUtilisationTimeChanged_,
        activityTotalIdleTimeChanged,
        activityTotalIdleTimeChanged_,
        activityUtilisationTimeChanged,
        activityUtilisationTimeChanged_,
        activityIdleTimeChanged,
        activityIdleTimeChanged_,
        activityUtilisationFactorChanged,
        activityUtilisationFactorChanged_,
        activityIdleFactorChanged,
        activityIdleFactorChanged_,
        -- * Basic Signals
        activityUtilising,
        activityUtilised,
        -- * Overall Signal
        activityChanged_) where

import Data.IORef
import Data.Monoid

import Control.Monad.Trans
import Control.Arrow

import Simulation.Aivika.Simulation
import Simulation.Aivika.Dynamics
import Simulation.Aivika.Internal.Event
import Simulation.Aivika.Internal.Signal
import Simulation.Aivika.Resource
import Simulation.Aivika.Cont
import Simulation.Aivika.Process
import Simulation.Aivika.Net
import Simulation.Aivika.Server
import Simulation.Aivika.Statistics

-- | Like 'Server' it models an activity that takes @a@ and provides @b@ having state @s@.
-- But unlike the former the activity is destined for simulation within 'Net' computation.
data Activity s a b =
  Activity { activityInitState :: s,
             -- ^ The initial state of the activity.
             activityStateRef :: IORef s,
             -- ^ The current state of the activity.
             activityProcess :: s -> a -> Process (s, b),
             -- ^ Provide @b@ by specified @a@.
             activityTotalUtilisationTimeRef :: IORef Double,
             -- ^ The counted total time of utilising the activity.
             activityTotalIdleTimeRef :: IORef Double,
             -- ^ The counted total time, when the activity was idle.
             activityUtilisationTimeRef :: IORef (SamplingStats Double),
             -- ^ The statistics for the utilisation time.
             activityIdleTimeRef :: IORef (SamplingStats Double),
             -- ^ The statistics for the time, when the activity was idle.
             activityUtilisingSource :: SignalSource a,
             -- ^ A signal raised when starting to utilise the activity.
             activityUtilisedSource :: SignalSource (a, b)
             -- ^ A signal raised when the activity has been utilised.
           }

-- | Create a new activity that can provide output @b@ by input @a@.
newActivity :: (a -> Process b)
               -- ^ provide an output by the specified input
               -> Simulation (Activity () a b)
newActivity provide =
  flip newStateActivity () $ \s a ->
  do b <- provide a
     return (s, b)

-- | Create a new activity that can provide output @b@ by input @a@
-- starting from state @s@.
newStateActivity :: (s -> a -> Process (s, b))
                    -- ^ provide a new state and output by the specified 
                    -- old state and input
                    -> s
                    -- ^ the initial state
                    -> Simulation (Activity s a b)
newStateActivity provide state =
  do r0 <- liftIO $ newIORef state
     r1 <- liftIO $ newIORef 0
     r2 <- liftIO $ newIORef 0
     r3 <- liftIO $ newIORef emptySamplingStats
     r4 <- liftIO $ newIORef emptySamplingStats
     s1 <- newSignalSource
     s2 <- newSignalSource
     return Activity { activityInitState = state,
                       activityStateRef = r0,
                       activityProcess = provide,
                       activityTotalUtilisationTimeRef = r1,
                       activityTotalIdleTimeRef = r2,
                       activityUtilisationTimeRef = r3,
                       activityIdleTimeRef = r4,
                       activityUtilisingSource = s1,
                       activityUtilisedSource = s2 }

-- | Return a network computation for the specified activity.
--
-- The computation updates the internal state of the activity. The usual case is when 
-- the computation is applied only once in a chain of data processing. Otherwise; 
-- every time the computation is used, the state of the activity changes. Sometimes 
-- it can be indeed useful if you want to aggregate the statistics for different 
-- activities simultaneously, but it would be more preferable to avoid this.
--
-- If you connect different activity computations returned by this function in a chain 
-- with help of '>>>' or other category combinator then this chain will act as one 
-- whole, where the first activity will take a new task only after the last activity 
-- finishes its current task and requests for the next one from the previous activity 
-- in the chain. This is not always that thing you might need.
activityNet :: Activity s a b -> Net a b
activityNet act = Net $ loop (activityInitState act) Nothing
  where
    loop s r a =
      do t0 <- liftDynamics time
         liftEvent $
           do case r of
                Nothing -> return ()
                Just t' ->
                  liftIO $
                  do modifyIORef' (activityTotalIdleTimeRef act) (+ (t0 - t'))
                     modifyIORef' (activityIdleTimeRef act) $
                       addSamplingStats (t0 - t')
              triggerSignal (activityUtilisingSource act) a
         -- utilise the activity
         (s', b) <- activityProcess act s a
         t1 <- liftDynamics time
         liftEvent $
           do liftIO $
                do writeIORef (activityStateRef act) $! s'
                   modifyIORef' (activityTotalUtilisationTimeRef act) (+ (t1 - t0))
                   modifyIORef' (activityUtilisationTimeRef act) $
                     addSamplingStats (t1 - t0)
              triggerSignal (activityUtilisedSource act) (a, b)
         return (b, Net $ loop s' (Just t1))

-- | Return the current state of the activity.
--
-- See also 'activityStateChanged' and 'activityStateChanged_'.
activityState :: Activity s a b -> Event s
activityState act =
  Event $ \p -> readIORef (activityStateRef act)
  
-- | Signal when the 'activityState' property value has changed.
activityStateChanged :: Activity s a b -> Signal s
activityStateChanged act =
  mapSignalM (const $ activityState act) (activityStateChanged_ act)
  
-- | Signal when the 'activityState' property value has changed.
activityStateChanged_ :: Activity s a b -> Signal ()
activityStateChanged_ act =
  mapSignal (const ()) (activityUtilised act)

-- | Return the counted total time when the activity was utilised.
--
-- The value returned changes discretely and it is usually delayed relative
-- to the current simulation time.
--
-- See also 'activityTotalUtilisationTimeChanged' and 'activityTotalUtilisationTimeChanged_'.
activityTotalUtilisationTime :: Activity s a b -> Event Double
activityTotalUtilisationTime act =
  Event $ \p -> readIORef (activityTotalUtilisationTimeRef act)
  
-- | Signal when the 'activityTotalUtilisationTime' property value has changed.
activityTotalUtilisationTimeChanged :: Activity s a b -> Signal Double
activityTotalUtilisationTimeChanged act =
  mapSignalM (const $ activityTotalUtilisationTime act) (activityTotalUtilisationTimeChanged_ act)
  
-- | Signal when the 'activityTotalUtilisationTime' property value has changed.
activityTotalUtilisationTimeChanged_ :: Activity s a b -> Signal ()
activityTotalUtilisationTimeChanged_ act =
  mapSignal (const ()) (activityUtilised act)

-- | Return the counted total time when the activity was idle.
--
-- The value returned changes discretely and it is usually delayed relative
-- to the current simulation time.
--
-- See also 'activityTotalIdleTimeChanged' and 'activityTotalIdleTimeChanged_'.
activityTotalIdleTime :: Activity s a b -> Event Double
activityTotalIdleTime act =
  Event $ \p -> readIORef (activityTotalIdleTimeRef act)
  
-- | Signal when the 'activityTotalIdleTime' property value has changed.
activityTotalIdleTimeChanged :: Activity s a b -> Signal Double
activityTotalIdleTimeChanged act =
  mapSignalM (const $ activityTotalIdleTime act) (activityTotalIdleTimeChanged_ act)
  
-- | Signal when the 'activityTotalIdleTime' property value has changed.
activityTotalIdleTimeChanged_ :: Activity s a b -> Signal ()
activityTotalIdleTimeChanged_ act =
  mapSignal (const ()) (activityUtilising act)

-- | Return the statistics for the time when the activity was utilised.
--
-- The value returned changes discretely and it is usually delayed relative
-- to the current simulation time.
--
-- See also 'activityUtilisationTimeChanged' and 'activityUtilisationTimeChanged_'.
activityUtilisationTime :: Activity s a b -> Event (SamplingStats Double)
activityUtilisationTime act =
  Event $ \p -> readIORef (activityUtilisationTimeRef act)
  
-- | Signal when the 'activityUtilisationTime' property value has changed.
activityUtilisationTimeChanged :: Activity s a b -> Signal (SamplingStats Double)
activityUtilisationTimeChanged act =
  mapSignalM (const $ activityUtilisationTime act) (activityUtilisationTimeChanged_ act)
  
-- | Signal when the 'activityUtilisationTime' property value has changed.
activityUtilisationTimeChanged_ :: Activity s a b -> Signal ()
activityUtilisationTimeChanged_ act =
  mapSignal (const ()) (activityUtilised act)

-- | Return the statistics for the time when the activity was idle.
--
-- The value returned changes discretely and it is usually delayed relative
-- to the current simulation time.
--
-- See also 'activityIdleTimeChanged' and 'activityIdleTimeChanged_'.
activityIdleTime :: Activity s a b -> Event (SamplingStats Double)
activityIdleTime act =
  Event $ \p -> readIORef (activityIdleTimeRef act)
  
-- | Signal when the 'activityIdleTime' property value has changed.
activityIdleTimeChanged :: Activity s a b -> Signal (SamplingStats Double)
activityIdleTimeChanged act =
  mapSignalM (const $ activityIdleTime act) (activityIdleTimeChanged_ act)
  
-- | Signal when the 'activityIdleTime' property value has changed.
activityIdleTimeChanged_ :: Activity s a b -> Signal ()
activityIdleTimeChanged_ act =
  mapSignal (const ()) (activityUtilising act)
  
-- | It returns the factor changing from 0 to 1, which estimates how often
-- the activity was utilised.
--
-- This factor is calculated as
--
-- @
--   totalUtilisationTime \/ (totalUtilisationTime + totalIdleTime)
-- @
--
-- As before in this module, the value returned changes discretely and
-- it is usually delayed relative to the current simulation time.
--
-- See also 'activityUtilisationFactorChanged' and 'activityUtilisationFactorChanged_'.
activityUtilisationFactor :: Activity s a b -> Event Double
activityUtilisationFactor act =
  Event $ \p ->
  do x1 <- readIORef (activityTotalUtilisationTimeRef act)
     x2 <- readIORef (activityTotalIdleTimeRef act)
     return (x1 / (x1 + x2))
  
-- | Signal when the 'activityUtilisationFactor' property value has changed.
activityUtilisationFactorChanged :: Activity s a b -> Signal Double
activityUtilisationFactorChanged act =
  mapSignalM (const $ activityUtilisationFactor act) (activityUtilisationFactorChanged_ act)
  
-- | Signal when the 'activityUtilisationFactor' property value has changed.
activityUtilisationFactorChanged_ :: Activity s a b -> Signal ()
activityUtilisationFactorChanged_ act =
  mapSignal (const ()) (activityUtilising act) <>
  mapSignal (const ()) (activityUtilised act)
  
-- | It returns the factor changing from 0 to 1, which estimates how often
-- the activity was idle.
--
-- This factor is calculated as
--
-- @
--   totalIdleTime \/ (totalUtilisationTime + totalIdleTime)
-- @
--
-- As before in this module, the value returned changes discretely and
-- it is usually delayed relative to the current simulation time.
--
-- See also 'activityIdleFactorChanged' and 'activityIdleFactorChanged_'.
activityIdleFactor :: Activity s a b -> Event Double
activityIdleFactor act =
  Event $ \p ->
  do x1 <- readIORef (activityTotalUtilisationTimeRef act)
     x2 <- readIORef (activityTotalIdleTimeRef act)
     return (x2 / (x1 + x2))
  
-- | Signal when the 'activityIdleFactor' property value has changed.
activityIdleFactorChanged :: Activity s a b -> Signal Double
activityIdleFactorChanged act =
  mapSignalM (const $ activityIdleFactor act) (activityIdleFactorChanged_ act)
  
-- | Signal when the 'activityIdleFactor' property value has changed.
activityIdleFactorChanged_ :: Activity s a b -> Signal ()
activityIdleFactorChanged_ act =
  mapSignal (const ()) (activityUtilising act) <>
  mapSignal (const ()) (activityUtilised act)

-- | Raised when starting to utilise the activity after a new input task is received.
activityUtilising :: Activity s a b -> Signal a
activityUtilising = publishSignal . activityUtilisingSource

-- | Raised when the activity has been utilised after the current task is processed.
activityUtilised :: Activity s a b -> Signal (a, b)
activityUtilised = publishSignal . activityUtilisedSource

-- | Signal whenever any property of the activity changes.
activityChanged_ :: Activity s a b -> Signal ()
activityChanged_ act =
  mapSignal (const ()) (activityUtilising act) <>
  mapSignal (const ()) (activityUtilised act)

-- | Return the summary for the activity with desciption of its
-- properties using the specified indent.
activitySummary :: Activity s a b -> Int -> Event ShowS
activitySummary act indent =
  Event $ \p ->
  do tx1 <- readIORef (activityTotalUtilisationTimeRef act)
     tx2 <- readIORef (activityTotalIdleTimeRef act)
     let xf1 = tx1 / (tx1 + tx2)
         xf2 = tx2 / (tx1 + tx2)
     xs1 <- readIORef (activityUtilisationTimeRef act)
     xs2 <- readIORef (activityIdleTimeRef act)
     let tab = replicate indent ' '
     return $
       showString tab .
       showString "total utilisation time = " . shows tx1 .
       showString "\n" .
       showString tab .
       showString "total idle time = " . shows tx2 .
       showString "\n" .
       showString tab .
       showString "utilisation factor (from 0 to 1) = " . shows xf1 .
       showString "\n" .
       showString tab .
       showString "idle factor (from 0 to 1) = " . shows xf2 .
       showString "\n" .
       showString tab .
       showString "utilisation time (locked while awaiting the input):\n\n" .
       samplingStatsSummary xs1 (2 + indent) .
       showString "\n\n" .
       showString tab .
       showString "idle time:\n\n" .
       samplingStatsSummary xs2 (2 + indent)