content: 
  -- |
  -- Module     : Simulation.Aivika.Queue.Infinite.Base
  -- Copyright  : Copyright (c) 2009-2017, David Sorokin <david.sorokin@gmail.com>
  -- License    : BSD3
  -- Maintainer : David Sorokin <david.sorokin@gmail.com>
  -- Stability  : experimental
  -- Tested with: GHC 8.0.1
  --
  -- This module defines an infinite optimised queue, which has no counters nor signals.
  --
  module Simulation.Aivika.Queue.Infinite.Base
         (-- * Queue Types
          FCFSQueue,
          LCFSQueue,
          SIROQueue,
          PriorityQueue,
          Queue,
          -- * Creating Queue
          newFCFSQueue,
          newLCFSQueue,
          newSIROQueue,
          newPriorityQueue,
          newQueue,
          -- * Queue Properties and Activities
          enqueueStoringStrategy,
          dequeueStrategy,
          queueNull,
          queueCount,
          -- * Dequeuing and Enqueuing
          dequeue,
          dequeueWithOutputPriority,
          tryDequeue,
          enqueue,
          enqueueWithStoringPriority,
          queueDelete,
          queueDelete_,
          queueDeleteBy,
          queueDeleteBy_,
          queueContains,
          queueContainsBy,
          clearQueue) where
  
  import Data.IORef
  import Data.Monoid
  import Data.Maybe
  
  import Control.Monad
  import Control.Monad.Trans
  
  import Simulation.Aivika.Internal.Specs
  import Simulation.Aivika.Internal.Simulation
  import Simulation.Aivika.Internal.Dynamics
  import Simulation.Aivika.Internal.Event
  import Simulation.Aivika.Internal.Process
  import Simulation.Aivika.Resource.Base
  import Simulation.Aivika.QueueStrategy
  
  import qualified Simulation.Aivika.DoubleLinkedList as DLL 
  import qualified Simulation.Aivika.Vector as V
  import qualified Simulation.Aivika.PriorityQueue as PQ
  
  -- | A type synonym for the ordinary FIFO queue also known as the FCFS
  -- (First Come - First Serviced) queue.
  type FCFSQueue a = Queue FCFS FCFS a
  
  -- | A type synonym for the ordinary LIFO queue also known as the LCFS
  -- (Last Come - First Serviced) queue.
  type LCFSQueue a = Queue LCFS FCFS a
  
  -- | A type synonym for the SIRO (Serviced in Random Order) queue.
  type SIROQueue a = Queue SIRO FCFS a
  
  -- | A type synonym for the queue with static priorities applied when
  -- storing the elements in the queue.
  type PriorityQueue a = Queue StaticPriorities FCFS a
  
  -- | Represents an infinite queue using the specified strategies for
  -- internal storing (in memory), @sm@, and dequeueing (output), @so@, where @a@ denotes
  -- the type of items stored in the queue.
  data Queue sm so a =
    Queue { enqueueStoringStrategy :: sm,
            -- ^ The strategy applied when storing (in memory) items in the queue.
            dequeueStrategy :: so,
            -- ^ The strategy applied to the dequeueing (output) processes.
            queueStore :: StrategyQueue sm a,
            dequeueRes :: Resource so,
            queueCountRef :: IORef Int }
    
  -- | Create a new infinite FCFS queue.  
  newFCFSQueue :: Simulation (FCFSQueue a)  
  newFCFSQueue = newQueue FCFS FCFS
    
  -- | Create a new infinite LCFS queue.  
  newLCFSQueue :: Simulation (LCFSQueue a)  
  newLCFSQueue = newQueue LCFS FCFS
    
  -- | Create a new infinite SIRO queue.  
  newSIROQueue :: Simulation (SIROQueue a)  
  newSIROQueue = newQueue SIRO FCFS
    
  -- | Create a new infinite priority queue.  
  newPriorityQueue :: Simulation (PriorityQueue a)  
  newPriorityQueue = newQueue StaticPriorities FCFS
    
  -- | Create a new infinite queue with the specified strategies.  
  newQueue :: (QueueStrategy sm,
               QueueStrategy so) =>
              sm
              -- ^ the strategy applied when storing items in the queue
              -> so
              -- ^ the strategy applied to the dequeueing (output) processes when the queue is empty
              -> Simulation (Queue sm so a)  
  newQueue sm so =
    do i  <- liftIO $ newIORef 0
       qm <- newStrategyQueue sm
       ro <- newResourceWithMaxCount so 0 Nothing
       return Queue { enqueueStoringStrategy = sm,
                      dequeueStrategy = so,
                      queueStore = qm,
                      dequeueRes = ro,
                      queueCountRef = i }
  
  -- | Test whether the queue is empty.
  --
  -- See also 'queueNullChanged' and 'queueNullChanged_'.
  queueNull :: Queue sm so a -> Event Bool
  queueNull q =
    Event $ \p ->
    do n <- readIORef (queueCountRef q)
       return (n == 0)
    
  -- | Return the current queue size.
  --
  -- See also 'queueCountStats', 'queueCountChanged' and 'queueCountChanged_'.
  queueCount :: Queue sm so a -> Event Int
  queueCount q =
    Event $ \p -> readIORef (queueCountRef q)
  
  -- | Dequeue suspending the process if the queue is empty.
  dequeue :: (DequeueStrategy sm,
              EnqueueStrategy so)
             => Queue sm so a
             -- ^ the queue
             -> Process a
             -- ^ the dequeued value
  dequeue q =
    do requestResource (dequeueRes q)
       liftEvent $ dequeueExtract q
    
  -- | Dequeue with the output priority suspending the process if the queue is empty.
  dequeueWithOutputPriority :: (DequeueStrategy sm,
                                PriorityQueueStrategy so po)
                               => Queue sm so a
                               -- ^ the queue
                               -> po
                               -- ^ the priority for output
                               -> Process a
                               -- ^ the dequeued value
  dequeueWithOutputPriority q po =
    do requestResourceWithPriority (dequeueRes q) po
       liftEvent $ dequeueExtract q
    
  -- | Try to dequeue immediately.
  tryDequeue :: DequeueStrategy sm
                => Queue sm so a
                -- ^ the queue
                -> Event (Maybe a)
                -- ^ the dequeued value of 'Nothing'
  tryDequeue q =
    do x <- tryRequestResourceWithinEvent (dequeueRes q)
       if x 
         then fmap Just $ dequeueExtract q
         else return Nothing
  
  -- | Remove the item from the queue and return a flag indicating
  -- whether the item was found and actually removed.
  queueDelete :: (Eq a,
                  DeletingQueueStrategy sm,
                  DequeueStrategy so)
                 => Queue sm so a
                 -- ^ the queue
                 -> a
                 -- ^ the item to remove from the queue
                 -> Event Bool
                 -- ^ whether the item was found and removed
  queueDelete q a = fmap isJust $ queueDeleteBy q (== a)
  
  -- | Remove the specified item from the queue.
  queueDelete_ :: (Eq a,
                   DeletingQueueStrategy sm,
                   DequeueStrategy so)
                  => Queue sm so a
                  -- ^ the queue
                  -> a
                  -- ^ the item to remove from the queue
                  -> Event ()
  queueDelete_ q a = fmap (const ()) $ queueDeleteBy q (== a)
  
  -- | Remove an item satisfying the specified predicate and return the item if found.
  queueDeleteBy :: (DeletingQueueStrategy sm,
                    DequeueStrategy so)
                   => Queue sm so a
                   -- ^ the queue
                   -> (a -> Bool)
                   -- ^ the predicate
                   -> Event (Maybe a)
  queueDeleteBy q pred =
    do x <- tryRequestResourceWithinEvent (dequeueRes q)
       if x
         then do i <- strategyQueueDeleteBy (queueStore q) pred
                 case i of
                   Nothing ->
                     do releaseResourceWithinEvent (dequeueRes q)
                        return Nothing
                   Just i ->
                     fmap Just $ dequeuePostExtract q i
         else return Nothing
                 
  -- | Remove an item satisfying the specified predicate.
  queueDeleteBy_ :: (DeletingQueueStrategy sm,
                     DequeueStrategy so)
                    => Queue sm so a
                    -- ^ the queue
                    -> (a -> Bool)
                    -- ^ the predicate
                    -> Event ()
  queueDeleteBy_ q pred = fmap (const ()) $ queueDeleteBy q pred
  
  -- | Detect whether the item is contained in the queue.
  queueContains :: (Eq a,
                    DeletingQueueStrategy sm)
                   => Queue sm so a
                   -- ^ the queue
                   -> a
                   -- ^ the item to search the queue for
                   -> Event Bool
                   -- ^ whether the item was found
  queueContains q a = fmap isJust $ queueContainsBy q (== a)
  
  -- | Detect whether an item satisfying the specified predicate is contained in the queue.
  queueContainsBy :: DeletingQueueStrategy sm
                     => Queue sm so a
                     -- ^ the queue
                     -> (a -> Bool)
                     -- ^ the predicate
                     -> Event (Maybe a)
                     -- ^ the item if it was found
  queueContainsBy q pred =
    strategyQueueContainsBy (queueStore q) pred
  
  -- | Clear the queue immediately.
  clearQueue :: DequeueStrategy sm
                => Queue sm so a
                -- ^ the queue
                -> Event ()
  clearQueue q =
    do x <- tryDequeue q
       case x of
         Nothing -> return ()
         Just a  -> clearQueue q
  
  -- | Enqueue the item.  
  enqueue :: (EnqueueStrategy sm,
              DequeueStrategy so)
             => Queue sm so a
             -- ^ the queue
             -> a
             -- ^ the item to enqueue
             -> Event ()
  enqueue = enqueueStore
       
  -- | Enqueue with the storing priority the item.  
  enqueueWithStoringPriority :: (PriorityQueueStrategy sm pm,
                                 DequeueStrategy so)
                                => Queue sm so a
                                -- ^ the queue
                                -> pm
                                -- ^ the priority for storing
                                -> a
                                -- ^ the item to enqueue
                                -> Event ()
  enqueueWithStoringPriority = enqueueStoreWithPriority
  
  -- | Store the item.
  enqueueStore :: (EnqueueStrategy sm,
                   DequeueStrategy so)
                  => Queue sm so a
                  -- ^ the queue
                  -> a
                  -- ^ the item to be stored
                  -> Event ()
  enqueueStore q a =
    Event $ \p ->
    do invokeEvent p $
         strategyEnqueue (queueStore q) a
       c <- readIORef (queueCountRef q)
       let c' = c + 1
       c' `seq` writeIORef (queueCountRef q) c'
       invokeEvent p $
         releaseResourceWithinEvent (dequeueRes q)
  
  -- | Store with the priority the item.
  enqueueStoreWithPriority :: (PriorityQueueStrategy sm pm,
                               DequeueStrategy so)
                              => Queue sm so a
                              -- ^ the queue
                              -> pm
                              -- ^ the priority for storing
                              -> a
                              -- ^ the item to be enqueued
                              -> Event ()
  enqueueStoreWithPriority q pm a =
    Event $ \p ->
    do invokeEvent p $
         strategyEnqueueWithPriority (queueStore q) pm a
       c <- readIORef (queueCountRef q)
       let c' = c + 1
       c' `seq` writeIORef (queueCountRef q) c'
       invokeEvent p $
         releaseResourceWithinEvent (dequeueRes q)
  
  -- | Extract an item for the dequeuing request.  
  dequeueExtract :: DequeueStrategy sm
                    => Queue sm so a
                    -- ^ the queue
                    -> Event a
                    -- ^ the dequeued value
  dequeueExtract q =
    Event $ \p ->
    do a <- invokeEvent p $
            strategyDequeue (queueStore q)
       invokeEvent p $
         dequeuePostExtract q a
  
  -- | A post action after extracting the item by the dequeuing request.  
  dequeuePostExtract :: DequeueStrategy sm
                        => Queue sm so a
                        -- ^ the queue
                        -> a
                        -- ^ the item to dequeue
                        -> Event a
                        -- ^ the dequeued value
  dequeuePostExtract q a =
    Event $ \p ->
    do c <- readIORef (queueCountRef q)
       let c' = c - 1
       c' `seq` writeIORef (queueCountRef q) c'
       return a
  