From a1043203bb4ef5bc1af4c9a8957af36d163f03fb Mon Sep 17 00:00:00 2001
From: Jasper Van der Jeugt <jaspervdj@gmail.com>
Date: Mon, 27 Dec 2010 18:38:46 +0100
Subject: Add a snapshot state to target monad

---
 src/Hakyll/Core/Target/Internal.hs | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

(limited to 'src/Hakyll')

diff --git a/src/Hakyll/Core/Target/Internal.hs b/src/Hakyll/Core/Target/Internal.hs
index dce4bfe..e68de33 100644
--- a/src/Hakyll/Core/Target/Internal.hs
+++ b/src/Hakyll/Core/Target/Internal.hs
@@ -12,6 +12,7 @@ module Hakyll.Core.Target.Internal
 import Control.Applicative (Applicative)
 import Control.Monad.Trans (MonadIO)
 import Control.Monad.Reader (ReaderT, runReaderT)
+import Control.Monad.State (StateT, evalStateT)
 
 import Hakyll.Core.Identifier
 import Hakyll.Core.ResourceProvider
@@ -30,11 +31,18 @@ data TargetEnvironment a = TargetEnvironment
     , targetStore            :: Store               -- ^ Store for caching
     }
 
+-- | State for the target monad
+--
+data TargetState = TargetState
+    { targetSnapshot :: Int  -- ^ Snapshot ID
+    }
+
 -- | Monad for targets. In this monad, the user can compose targets and describe
 -- how they should be created.
 --
-newtype TargetM a b = TargetM {unTargetM :: ReaderT (TargetEnvironment a) IO b}
-                    deriving (Monad, Functor, Applicative, MonadIO)
+newtype TargetM a b = TargetM
+    { unTargetM :: ReaderT (TargetEnvironment a) (StateT TargetState IO) b
+    } deriving (Monad, Functor, Applicative, MonadIO)
 
 -- | Simplification of the 'TargetM' type for concrete cases: the type of the
 -- returned item should equal the type of the dependencies.
@@ -49,7 +57,8 @@ runTarget :: Target a
           -> ResourceProvider
           -> Store
           -> IO a
-runTarget target id' lookup' provider store = runReaderT (unTargetM target) env
+runTarget target id' lookup' provider store =
+    evalStateT (runReaderT (unTargetM target) env) state
   where
     env = TargetEnvironment
         { targetIdentifier       = id'
@@ -57,3 +66,6 @@ runTarget target id' lookup' provider store = runReaderT (unTargetM target) env
         , targetResourceProvider = provider
         , targetStore            = store
         }
+    state = TargetState
+        { targetSnapshot = 0
+        }
-- 
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