-- Implements the logical AND 
module QuicQuid.Agent.And(andAgent) where

import Control.Concurrent
import Control.Monad(forever)
import QuicQuid.Router
import qualified Data.Map as M

import QuicQuid.Log
import QuicQuid.Logic
import QuicQuid.Agent.Util

-- BUG: security problem, 'and' can be taken over by rogue agents.
-- BUG: spawn agents are never stopped.
-- BUG: inefficient, an agent for every combination of results?
andAgent = answerAgent "and" "and ?preds" process     
   where process qch = do   
          (bs,replyCh)  <- readAskChan qch
          let Just (Arr preds) = M.lookup "preds" bs 
          andQuery M.empty preds replyCh

andQuery bs []     outChan = write outChan $ Obj bs
andQuery bs (q:qs) outChan = do
     debugM "QuicQuid.Agent.And.andQuery" $ show bs ++ " " ++ show (q:qs) 
     forkIO $ do
             (ch,chName) <- newEndPoint "/tmp"  
             newQuery_ q chName
             forever $ do
               Obj nbs <- readBody ch
               andQuery (M.union bs nbs) (map (substitute nbs) qs) outChan
     return ()