{-# LANGUAGE   DeriveDataTypeable
             , FlexibleContexts
             , ScopedTypeVariables
             , CPP
{-# OPTIONS -IControl/Workflow       #-}

{- | This module contains monadic combinators that express some workflow patterns.
see the docAprobal.hs example included in the package

Here  the constraint `DynSerializer w r a` is equivalent to  `Data.Refserialize a`
This version permits optimal (de)serialization if you store in the queue different versions of largue structures, for
example, documents.  You must  define the right RefSerialize instance however.
See an example in docAprobal.hs incuded in the paclkage.
Alternatively you can use  Data.Binary serlializatiion with Control.Workflow.Binary.Patterns


This fragment below describes the approbal procedure of a document.
First the document reference is sent to a list of bosses trough a queue.
ithey return a boolean in a  return queue ( askUser)
the booleans are summed up according with a monoid instance (sumUp)

if the resullt is false, the correctWF workflow is executed
If the result is True, the pipeline continues to the next stage  (checkValidated)

the next stage is the same process with a new list of users (superbosses).
This time, there is a timeout of 7 days. the result of the users that voted is summed
up according with the same monoid instance

if the result is true the document is added to the persistent list of approbed documents
if the result is false, the document is added to the persistent list of rejectec documents (checlkValidated1)

@docApprobal :: Document -> Workflow IO ()
docApprobal doc =  `getWFRef` \>>= docApprobal1

docApprobal1 rdoc=
    return True \>>=
    log \"requesting approbal from bosses\" \>>=
    `sumUp` 0 (map (askUser doc rdoc) bosses)  \>>=
    checkValidated \>>=
    log \"requesting approbal from superbosses or timeout\"  \>>=
    `sumUp` (7*60*60*24) (map(askUser doc rdoc) superbosses) \>>=

askUser _ _ user False = return False
askUser doc rdoc user  True =  do
      `step` $ `push` (quser user) rdoc
      `logWF` ("wait for any response from the user: " ++ user)
      `step` . `pop` $ qdocApprobal (title doc)

log txt x = `logWF` txt >> return x

checkValidated :: Bool -> `Workflow` IO Bool
checkValidated  val =
      case val of
        False -> correctWF (title doc) rdoc >> return False
        _     -> return True

checkValidated1 :: Bool -> Workflow IO ()
checkValidated1 val = step $ do
      case  val of
        False -> `push` qrejected doc
        _     -> `push` qapproved doc
      mapM (\u ->deleteFromQueue (quser u) rdoc) superbosses@


module Control.Workflow.Text.Patterns(
-- * Low level combinators
split, merge, select,
-- * High level conbinators
vote, sumUp, Select(..)
) where
import Control.Concurrent.STM
import Data.Monoid
import Control.Concurrent.MonadIO
import qualified Control.Monad.CatchIO as CMC
import Control.Workflow.Stat
import Control.Workflow.Text
import Data.Typeable
import Prelude hiding (catch)
import Control.Monad(when)
import Control.Exception.Extensible (Exception)
import Control.Workflow.GenSerializer
import Control.Workflow.Stat
import Debug.Trace
import Data.TCache

a !> b = trace b a

#include "Patterns.inc.hs"