Merge branch 'master' into dependency-analyzer

17 files changed, 269 insertions, 130 deletions

diff --git a/src/Hakyll.hs b/src/Hakyll.hs
index 5fe1f26..341bb53 100644
--- a/src/Hakyll.hs
+++ b/src/Hakyll.hs
@@ -5,7 +5,8 @@ module Hakyll
     , module Hakyll.Core.Configuration
     , module Hakyll.Core.Identifier
     , module Hakyll.Core.Identifier.Pattern
-    , module Hakyll.Core.ResourceProvider
+    , module Hakyll.Core.Resource
+    , module Hakyll.Core.Resource.Provider
     , module Hakyll.Core.Routes
     , module Hakyll.Core.Rules
     , module Hakyll.Core.UnixFilter
@@ -34,7 +35,8 @@ import Hakyll.Core.Compiler
 import Hakyll.Core.Configuration
 import Hakyll.Core.Identifier
 import Hakyll.Core.Identifier.Pattern
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
+import Hakyll.Core.Resource.Provider
 import Hakyll.Core.Routes
 import Hakyll.Core.Rules
 import Hakyll.Core.UnixFilter
diff --git a/src/Hakyll/Core/Compiler.hs b/src/Hakyll/Core/Compiler.hs
index 371594f..db51131 100644
--- a/src/Hakyll/Core/Compiler.hs
+++ b/src/Hakyll/Core/Compiler.hs
@@ -124,7 +124,8 @@ import Hakyll.Core.Identifier
 import Hakyll.Core.Identifier.Pattern
 import Hakyll.Core.CompiledItem
 import Hakyll.Core.Writable
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
+import Hakyll.Core.Resource.Provider
 import Hakyll.Core.Compiler.Internal
 import Hakyll.Core.Store
 import Hakyll.Core.Rules.Internal
@@ -237,7 +238,7 @@ requireAll_ :: (Binary a, Typeable a, Writable a)
             -> Compiler b [a]
 requireAll_ pattern = fromDependencies (const getDeps) >>> fromJob requireAll_'
   where
-    getDeps = matches pattern . map unResource . resourceList
+    getDeps = filterMatches pattern . map unResource . resourceList
     requireAll_' = const $ CompilerM $ do
         deps <- getDeps . compilerResourceProvider <$> ask
         mapM (unCompilerM . getDependency) deps
diff --git a/src/Hakyll/Core/Compiler/Internal.hs b/src/Hakyll/Core/Compiler/Internal.hs
index 4eef91c..1a3c4c3 100644
--- a/src/Hakyll/Core/Compiler/Internal.hs
+++ b/src/Hakyll/Core/Compiler/Internal.hs
@@ -26,7 +26,7 @@ import Control.Category (Category, (.), id)
 import Control.Arrow (Arrow, ArrowChoice, arr, first, left)
 
 import Hakyll.Core.Identifier
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource.Provider
 import Hakyll.Core.Store
 import Hakyll.Core.Routes
 import Hakyll.Core.Logger
diff --git a/src/Hakyll/Core/Identifier/Pattern.hs b/src/Hakyll/Core/Identifier/Pattern.hs
index a1e36df..8f3ac01 100644
--- a/src/Hakyll/Core/Identifier/Pattern.hs
+++ b/src/Hakyll/Core/Identifier/Pattern.hs
@@ -1,4 +1,12 @@
 -- | Module providing pattern matching and capturing on 'Identifier's.
+-- 'Pattern's come in two kinds:
+--
+-- * Simple glob patterns, like @foo\/*@;
+--
+-- * Custom, arbitrary predicates of the type @Identifier -> Bool@.
+--
+-- They both have advantages and disadvantages. By default, globs are used,
+-- unless you construct your 'Pattern' using the 'predicate' function.
 --
 -- A very simple pattern could be, for example, @foo\/bar@. This pattern will
 -- only match the exact @foo\/bar@ identifier.
@@ -20,15 +28,17 @@
 --
 -- * @foo\/*.html@ will match all HTML files in the @foo\/@ directory.
 --
--- The 'match' function allows the user to get access to the elements captured
+-- The 'capture' function allows the user to get access to the elements captured
 -- by the capture elements in the pattern.
 --
 module Hakyll.Core.Identifier.Pattern
     ( Pattern
-    , parsePattern
-    , match
-    , doesMatch
+    , parseGlob
+    , predicate
+    , regex
     , matches
+    , filterMatches
+    , capture
     , fromCapture
     , fromCaptureString
     , fromCaptures
@@ -37,32 +47,39 @@ module Hakyll.Core.Identifier.Pattern
 import Data.List (isPrefixOf, inits, tails)
 import Control.Arrow ((&&&), (>>>))
 import Control.Monad (msum)
-import Data.Maybe (isJust)
-import Data.Monoid (mempty, mappend)
+import Data.Maybe (isJust, fromMaybe)
+import Data.Monoid (Monoid, mempty, mappend)
 
 import GHC.Exts (IsString, fromString)
+import Text.Regex.PCRE ((=~~))
 
 import Hakyll.Core.Identifier
 
 -- | One base element of a pattern
 --
-data PatternComponent = Capture
-                      | CaptureMany
-                      | Literal String
-                      deriving (Eq, Show)
+data GlobComponent = Capture
+                   | CaptureMany
+                   | Literal String
+                   deriving (Eq, Show)
 
 -- | Type that allows matching on identifiers
 --
-newtype Pattern = Pattern {unPattern :: [PatternComponent]}
-                deriving (Eq, Show)
+data Pattern = Glob [GlobComponent]
+             | Predicate (Identifier -> Bool)
 
 instance IsString Pattern where
-    fromString = parsePattern
+    fromString = parseGlob
+
+instance Monoid Pattern where
+    mempty = Predicate (const True)
+    g@(Glob _)  `mappend` x           = Predicate (matches g) `mappend` x
+    x           `mappend` g@(Glob _)  = x `mappend` Predicate (matches g)
+    Predicate f `mappend` Predicate g = Predicate $ \i -> f i && g i
 
 -- | Parse a pattern from a string
 --
-parsePattern :: String -> Pattern
-parsePattern = Pattern . parse' -- undefined -- Pattern . map toPattern . unIdentifier . parseIdentifier
+parseGlob :: String -> Pattern
+parseGlob = Glob . parse'
   where
     parse' str =
         let (chunk, rest) = break (`elem` "\\*") str
@@ -72,20 +89,34 @@ parsePattern = Pattern . parse' -- undefined -- Pattern . map toPattern . unIden
             ('*'  : xs)       -> Literal chunk : Capture : parse' xs
             xs                -> Literal chunk : Literal xs : []
 
--- | Match an identifier against a pattern, generating a list of captures
+-- | Create a 'Pattern' from an arbitrary predicate
+--
+-- Example:
+--
+-- > predicate (\i -> matches "foo/*" i && not (matches "foo/bar" i))
+--
+predicate :: (Identifier -> Bool) -> Pattern
+predicate = Predicate
+
+-- | Create a 'Pattern' from a regex
+--
+-- Example:
+--
+-- > regex "^foo/[^x]*$
 --
-match :: Pattern -> Identifier -> Maybe [Identifier]
-match p (Identifier i) = fmap (map Identifier) $ match' (unPattern p) i
+regex :: String -> Pattern
+regex str = predicate $ fromMaybe False . (=~~ str) . toFilePath
 
 -- | Check if an identifier matches a pattern
 --
-doesMatch :: Pattern -> Identifier -> Bool
-doesMatch p = isJust . match p
+matches :: Pattern -> Identifier -> Bool
+matches (Glob p)      = isJust . capture (Glob p)
+matches (Predicate p) = (p $)
 
 -- | Given a list of identifiers, retain only those who match the given pattern
 --
-matches :: Pattern -> [Identifier] -> [Identifier]
-matches p = filter (doesMatch p)
+filterMatches :: Pattern -> [Identifier] -> [Identifier]
+filterMatches = filter . matches
 
 -- | Split a list at every possible point, generate a list of (init, tail)
 -- cases. The result is sorted with inits decreasing in length.
@@ -93,30 +124,35 @@ matches p = filter (doesMatch p)
 splits :: [a] -> [([a], [a])]
 splits = inits &&& tails >>> uncurry zip >>> reverse
 
--- | Internal verion of 'match'
+-- | Match a glob against a pattern, generating a list of captures
 --
-match' :: [PatternComponent] -> String -> Maybe [String]
-match' [] [] = Just []  -- An empty match
-match' [] _  = Nothing  -- No match
--- match' _  [] = Nothing   -- No match
-match' (Literal l : ms) str
+capture :: Pattern -> Identifier -> Maybe [Identifier]
+capture (Glob p) (Identifier i) = fmap (map Identifier) $ capture' p i
+capture (Predicate _) _         = Nothing
+
+-- | Internal verion of 'capture'
+--
+capture' :: [GlobComponent] -> String -> Maybe [String]
+capture' [] [] = Just []  -- An empty match
+capture' [] _  = Nothing  -- No match
+capture' (Literal l : ms) str
     -- Match the literal against the string
-    | l `isPrefixOf` str = match' ms $ drop (length l) str
+    | l `isPrefixOf` str = capture' ms $ drop (length l) str
     | otherwise          = Nothing
-match' (Capture : ms) str =
+capture' (Capture : ms) str =
     -- Match until the next /
     let (chunk, rest) = break (== '/') str
-    in msum $ [ fmap (i :) (match' ms (t ++ rest)) | (i, t) <- splits chunk ]
-match' (CaptureMany : ms) str =
+    in msum $ [ fmap (i :) (capture' ms (t ++ rest)) | (i, t) <- splits chunk ]
+capture' (CaptureMany : ms) str =
     -- Match everything
-    msum $ [ fmap (i :) (match' ms t) | (i, t) <- splits str ]
+    msum $ [ fmap (i :) (capture' ms t) | (i, t) <- splits str ]
     
 -- | Create an identifier from a pattern by filling in the captures with a given
 -- string
 --
 -- Example:
 --
--- > fromCapture (parsePattern "tags/*") (parseIdentifier "foo")
+-- > fromCapture (parseGlob "tags/*") (parseIdentifier "foo")
 --
 -- Result:
 --
@@ -128,7 +164,7 @@ fromCapture pattern = fromCaptures pattern . repeat
 -- | Simplified version of 'fromCapture' which takes a 'String' instead of an
 -- 'Identifier'
 --
--- > fromCaptureString (parsePattern "tags/*") "foo"
+-- > fromCaptureString (parseGlob "tags/*") "foo"
 --
 -- Result:
 --
@@ -141,11 +177,19 @@ fromCaptureString pattern = fromCapture pattern . parseIdentifier
 -- given list of strings
 --
 fromCaptures :: Pattern -> [Identifier] -> Identifier
-fromCaptures (Pattern []) _ = mempty
-fromCaptures (Pattern (m : ms)) [] = case m of
-    Literal l -> Identifier l `mappend` fromCaptures (Pattern ms) []
-    _         -> error $  "Hakyll.Core.Identifier.Pattern.fromCaptures: "
+fromCaptures (Glob p)      = fromCaptures' p
+fromCaptures (Predicate _) = error $
+    "Hakyll.Core.Identifier.Pattern.fromCaptures: fromCaptures called on a " ++
+    "predicate instead of a glob"
+
+-- | Internally used version of 'fromCaptures'
+--
+fromCaptures' :: [GlobComponent] -> [Identifier] -> Identifier
+fromCaptures' []        _ = mempty
+fromCaptures' (m : ms) [] = case m of
+    Literal l -> Identifier l `mappend` fromCaptures' ms []
+    _         -> error $  "Hakyll.Core.Identifier.Pattern.fromCaptures': "
                        ++ "identifier list exhausted"
-fromCaptures (Pattern (m : ms)) ids@(i : is) = case m of
-    Literal l -> Identifier l `mappend` fromCaptures (Pattern ms) ids
-    _         -> i `mappend` fromCaptures (Pattern ms) is
+fromCaptures' (m : ms) ids@(i : is) = case m of
+    Literal l -> Identifier l `mappend` fromCaptures' ms ids
+    _         -> i `mappend` fromCaptures' ms is
diff --git a/src/Hakyll/Core/Resource.hs b/src/Hakyll/Core/Resource.hs
new file mode 100644
index 0000000..d60fda9
--- /dev/null
+++ b/src/Hakyll/Core/Resource.hs
@@ -0,0 +1,14 @@
+-- | Module exporting the simple 'Resource' type
+--
+module Hakyll.Core.Resource
+    ( Resource (..)
+    ) where
+
+import Hakyll.Core.Identifier
+
+-- | A resource
+--
+-- Invariant: the resource specified by the given identifier must exist
+--
+newtype Resource = Resource {unResource :: Identifier}
+                 deriving (Eq, Show, Ord)
diff --git a/src/Hakyll/Core/ResourceProvider.hs b/src/Hakyll/Core/Resource/Provider.hs
index dcd4af0..90e93f8 100644
--- a/src/Hakyll/Core/ResourceProvider.hs
+++ b/src/Hakyll/Core/Resource/Provider.hs
@@ -10,16 +10,18 @@
 -- Therefore, it is not recommended to read files directly -- you should use the
 -- provided 'Resource' methods.
 --
-module Hakyll.Core.ResourceProvider
-    ( Resource (..)
-    , ResourceProvider (..)
+module Hakyll.Core.Resource.Provider
+    ( ResourceProvider (..)
     , resourceExists
     , resourceDigest
     , resourceModified
     ) where
 
+import Control.Concurrent (MVar, readMVar, modifyMVar_)
 import Control.Monad ((<=<))
 import Data.Word (Word8)
+import Data.Map (Map)
+import qualified Data.Map as M
 
 import qualified Data.ByteString.Lazy as LB
 import OpenSSL.Digest.ByteString.Lazy (digest)
@@ -27,13 +29,7 @@ import OpenSSL.Digest (MessageDigest (MD5))
 
 import Hakyll.Core.Identifier
 import Hakyll.Core.Store
-
--- | A resource
---
--- Invariant: the resource specified by the given identifier must exist
---
-newtype Resource = Resource {unResource :: Identifier}
-                 deriving (Eq, Show, Ord)
+import Hakyll.Core.Resource
 
 -- | A value responsible for retrieving and listing resources
 --
@@ -44,6 +40,8 @@ data ResourceProvider = ResourceProvider
       resourceString         :: Resource -> IO String
     , -- | Retrieve a certain resource as lazy bytestring
       resourceLazyByteString :: Resource -> IO LB.ByteString
+    , -- | Cache keeping track of modified items
+      resourceModifiedCache  :: MVar (Map Resource Bool)
     }
 
 -- | Check if a given identifier has a resource
@@ -60,6 +58,24 @@ resourceDigest provider = digest MD5 <=< resourceLazyByteString provider
 --
 resourceModified :: ResourceProvider -> Resource -> Store -> IO Bool
 resourceModified provider resource store = do
+    cache <- readMVar mvar
+    case M.lookup resource cache of
+        -- Already in the cache
+        Just m  -> return m
+        -- Not yet in the cache, check digests (if it exists)
+        Nothing -> do
+            m <- if resourceExists provider (unResource resource)
+                        then digestModified provider resource store
+                        else return False
+            modifyMVar_ mvar (return . M.insert resource m)
+            return m
+  where
+    mvar = resourceModifiedCache provider
+
+-- | Check if a resource digest was modified
+--
+digestModified :: ResourceProvider -> Resource -> Store -> IO Bool
+digestModified provider resource store = do
     -- Get the latest seen digest from the store
     lastDigest <- storeGet store itemName $ unResource resource
     -- Calculate the digest for the resource
@@ -72,4 +88,4 @@ resourceModified provider resource store = do
         else do storeSet store itemName (unResource resource) newDigest
                 return True
   where
-    itemName = "Hakyll.Core.ResourceProvider.resourceModified"
+    itemName = "Hakyll.Core.ResourceProvider.digestModified"
diff --git a/src/Hakyll/Core/ResourceProvider/FileResourceProvider.hs b/src/Hakyll/Core/Resource/Provider/File.hs
index 0d89b21..953d61c 100644
--- a/src/Hakyll/Core/ResourceProvider/FileResourceProvider.hs
+++ b/src/Hakyll/Core/Resource/Provider/File.hs
@@ -1,14 +1,17 @@
 -- | A concrete 'ResourceProvider' that gets it's resources from the filesystem
 --
-module Hakyll.Core.ResourceProvider.FileResourceProvider
+module Hakyll.Core.Resource.Provider.File
     ( fileResourceProvider
     ) where
 
 import Control.Applicative ((<$>))
+import Control.Concurrent (newMVar)
+import qualified Data.Map as M
 
 import qualified Data.ByteString.Lazy as LB
 
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
+import Hakyll.Core.Resource.Provider
 import Hakyll.Core.Identifier
 import Hakyll.Core.Util.File
 import Hakyll.Core.Configuration
@@ -21,9 +24,13 @@ fileResourceProvider configuration = do
     list <- map parseIdentifier . filter (not . ignoreFile configuration) <$>
         getRecursiveContents False "."
 
+    -- MVar for the cache
+    mvar <- newMVar M.empty
+
     -- Construct a resource provider
     return ResourceProvider
         { resourceList           = map Resource list
         , resourceString         = readFile . toFilePath . unResource
         , resourceLazyByteString = LB.readFile . toFilePath . unResource
+        , resourceModifiedCache  = mvar
         }
diff --git a/src/Hakyll/Core/Routes.hs b/src/Hakyll/Core/Routes.hs
index fcab28d..abbd0a7 100644
--- a/src/Hakyll/Core/Routes.hs
+++ b/src/Hakyll/Core/Routes.hs
@@ -30,7 +30,7 @@ module Hakyll.Core.Routes
     , runRoutes
     , idRoute
     , setExtension
-    , ifMatch
+    , matchRoute
     , customRoute
     , gsubRoute
     , composeRoutes
@@ -85,15 +85,15 @@ setExtension :: String -> Routes
 setExtension extension = Routes $ fmap (`replaceExtension` extension)
                                 . unRoutes idRoute
 
--- | Modify a route: apply the route if the identifier matches the given
--- pattern, fail otherwise.
+-- | Apply the route if the identifier matches the given pattern, fail
+-- otherwise
 --
-ifMatch :: Pattern -> Routes -> Routes
-ifMatch pattern (Routes route) = Routes $ \id' ->
-    if doesMatch pattern id' then route id'
-                             else Nothing
+matchRoute :: Pattern -> Routes -> Routes
+matchRoute pattern (Routes route) = Routes $ \id' ->
+    if matches pattern id' then route id' else Nothing
 
--- | Create a custom route. This should almost always be used with 'ifMatch'.
+-- | Create a custom route. This should almost always be used with
+-- 'matchRoute'
 --
 customRoute :: (Identifier -> FilePath) -> Routes
 customRoute f = Routes $ Just . f
diff --git a/src/Hakyll/Core/Rules.hs b/src/Hakyll/Core/Rules.hs
index eba3fb9..892cf7c 100644
--- a/src/Hakyll/Core/Rules.hs
+++ b/src/Hakyll/Core/Rules.hs
@@ -7,13 +7,18 @@
 -- A typical usage example would be:
 --
 -- > main = hakyll $ do
--- >     route   "posts/*" (setExtension "html")
--- >     compile "posts/*" someCompiler
+-- >     match "posts/*" $ do
+-- >         route   (setExtension "html")
+-- >         compile someCompiler
+-- >     match "css/*" $ do
+-- >         route   idRoute
+-- >         compile compressCssCompiler
 --
 {-# LANGUAGE GeneralizedNewtypeDeriving, OverloadedStrings #-}
 module Hakyll.Core.Rules
     ( RulesM
     , Rules
+    , match
     , compile
     , create
     , route
@@ -23,16 +28,17 @@ module Hakyll.Core.Rules
 
 import Control.Applicative ((<$>))
 import Control.Monad.Writer (tell)
-import Control.Monad.Reader (ask)
+import Control.Monad.Reader (ask, local)
 import Control.Arrow (second, (>>>), arr, (>>^))
 import Control.Monad.State (get, put)
-import Data.Monoid (mempty)
+import Data.Monoid (mempty, mappend)
 import qualified Data.Set as S
 
 import Data.Typeable (Typeable)
 import Data.Binary (Binary)
 
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
+import Hakyll.Core.Resource.Provider
 import Hakyll.Core.Identifier
 import Hakyll.Core.Identifier.Pattern
 import Hakyll.Core.Compiler.Internal
@@ -63,21 +69,32 @@ tellResources :: [Resource]
               -> Rules
 tellResources resources = RulesM $ tell $ RuleSet mempty mempty $ S.fromList resources
 
+-- | Only compile/route items satisfying the given predicate
+--
+match :: Pattern -> Rules -> Rules
+match pattern = RulesM . local addPredicate . unRulesM
+  where
+    addPredicate env = env
+        { rulesPattern = rulesPattern env `mappend` pattern
+        }
+
 -- | Add a compilation rule to the rules.
 --
--- This instructs all resources matching the given pattern to be compiled using
--- the given compiler. When no resources match the given pattern, nothing will
--- happen. In this case, you might want to have a look at 'create'.
+-- This instructs all resources to be compiled using the given compiler. When
+-- no resources match the current selection, nothing will happen. In this case,
+-- you might want to have a look at 'create'.
 --
 compile :: (Binary a, Typeable a, Writable a)
-        => Pattern -> Compiler Resource a -> Rules
-compile pattern compiler = RulesM $ do
-    identifiers <- matches pattern . map unResource . resourceList <$> ask
+        => Compiler Resource a -> Rules
+compile compiler = RulesM $ do
+    pattern <- rulesPattern <$> ask
+    provider <- rulesResourceProvider <$> ask
+    let ids = filterMatches pattern $ map unResource $ resourceList provider
     unRulesM $ do
-        tellCompilers $ flip map identifiers $ \identifier ->
+        tellCompilers $ flip map ids $ \identifier ->
             (identifier, constA (Resource identifier) >>> compiler)
-        tellResources $ map Resource identifiers
-
+        tellResources $ map Resource ids
+                   
 -- | Add a compilation rule
 --
 -- This sets a compiler for the given identifier. No resource is needed, since
@@ -91,10 +108,12 @@ create identifier compiler = tellCompilers [(identifier, compiler)]
 
 -- | Add a route.
 --
--- This adds a route for all items matching the given pattern.
+-- This adds a route for all items matching the current pattern.
 --
-route :: Pattern -> Routes -> Rules
-route pattern route' = tellRoute $ ifMatch pattern route'
+route :: Routes -> Rules
+route route' = RulesM $ do
+    pattern <- rulesPattern <$> ask
+    unRulesM $ tellRoute $ matchRoute pattern route'
 
 -- | Apart from regular compilers, one is also able to specify metacompilers.
 -- Metacompilers are a special class of compilers: they are compilers which
diff --git a/src/Hakyll/Core/Rules/Internal.hs b/src/Hakyll/Core/Rules/Internal.hs
index 2895257..0e117ec 100644
--- a/src/Hakyll/Core/Rules/Internal.hs
+++ b/src/Hakyll/Core/Rules/Internal.hs
@@ -5,6 +5,7 @@ module Hakyll.Core.Rules.Internal
     ( CompileRule (..)
     , RuleSet (..)
     , RuleState (..)
+    , RuleEnvironment (..)
     , RulesM (..)
     , Rules
     , runRules
@@ -17,8 +18,10 @@ import Control.Monad.State (State, evalState)
 import Data.Monoid (Monoid, mempty, mappend)
 import Data.Set (Set)
 
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
+import Hakyll.Core.Resource.Provider
 import Hakyll.Core.Identifier
+import Hakyll.Core.Identifier.Pattern
 import Hakyll.Core.Compiler.Internal
 import Hakyll.Core.Routes
 import Hakyll.Core.CompiledItem
@@ -55,10 +58,17 @@ data RuleState = RuleState
     { rulesMetaCompilerIndex :: Int
     } deriving (Show)
 
+-- | Rule environment
+--
+data RuleEnvironment = RuleEnvironment
+    { rulesResourceProvider :: ResourceProvider
+    , rulesPattern          :: Pattern
+    }
+
 -- | The monad used to compose rules
 --
 newtype RulesM a = RulesM
-    { unRulesM :: ReaderT ResourceProvider (WriterT RuleSet (State RuleState)) a
+    { unRulesM :: ReaderT RuleEnvironment (WriterT RuleSet (State RuleState)) a
     } deriving (Monad, Functor, Applicative)
 
 -- | Simplification of the RulesM type; usually, it will not return any
@@ -70,6 +80,9 @@ type Rules = RulesM ()
 --
 runRules :: Rules -> ResourceProvider -> RuleSet
 runRules rules provider =
-    evalState (execWriterT $ runReaderT (unRulesM rules) provider) state
+    evalState (execWriterT $ runReaderT (unRulesM rules) env) state
   where
     state = RuleState {rulesMetaCompilerIndex = 0}
+    env = RuleEnvironment { rulesResourceProvider = provider
+                          , rulesPattern          = mempty
+                          }
diff --git a/src/Hakyll/Core/Run.hs b/src/Hakyll/Core/Run.hs
index 58fd49a..c2cc21b 100644
--- a/src/Hakyll/Core/Run.hs
+++ b/src/Hakyll/Core/Run.hs
@@ -25,8 +25,9 @@ import Hakyll.Core.Identifier
 import Hakyll.Core.Util.File
 import Hakyll.Core.Compiler
 import Hakyll.Core.Compiler.Internal
-import Hakyll.Core.ResourceProvider
-import Hakyll.Core.ResourceProvider.FileResourceProvider
+import Hakyll.Core.Resource
+import Hakyll.Core.Resource.Provider
+import Hakyll.Core.Resource.Provider.File
 import Hakyll.Core.Rules.Internal
 import Hakyll.Core.DirectedGraph
 import Hakyll.Core.DirectedGraph.Dot
@@ -108,9 +109,7 @@ modified :: ResourceProvider     -- ^ Resource provider
          -> [Identifier]         -- ^ Identifiers to check
          -> IO (Set Identifier)  -- ^ Modified resources
 modified provider store ids = fmap S.fromList $ flip filterM ids $ \id' ->
-    if resourceExists provider id'
-        then resourceModified provider (Resource id') store
-        else return False
+    resourceModified provider (Resource id') store
 
 -- | Add a number of compilers and continue using these compilers
 --
diff --git a/src/Hakyll/Core/Util/File.hs b/src/Hakyll/Core/Util/File.hs
index 9babc8b..24814ae 100644
--- a/src/Hakyll/Core/Util/File.hs
+++ b/src/Hakyll/Core/Util/File.hs
@@ -47,7 +47,7 @@ getRecursiveContents includeDirs topdir = do
             return $ if includeDirs then topdir : concat paths
                                     else concat paths
   where
-    isProper = not . (== ".") . take 1
+    isProper = (`notElem` [".", ".."])
 
 -- | Check if a timestamp is obsolete compared to the timestamps of a number of
 -- files. When they are no files, it is never obsolete.
diff --git a/src/Hakyll/Core/Writable/CopyFile.hs b/src/Hakyll/Core/Writable/CopyFile.hs
index 1cd5fd2..ab9c698 100644
--- a/src/Hakyll/Core/Writable/CopyFile.hs
+++ b/src/Hakyll/Core/Writable/CopyFile.hs
@@ -12,7 +12,7 @@ import System.Directory (copyFile)
 import Data.Typeable (Typeable)
 import Data.Binary (Binary)
 
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
 import Hakyll.Core.Writable
 import Hakyll.Core.Compiler
 import Hakyll.Core.Identifier
diff --git a/src/Hakyll/Web/CompressCss.hs b/src/Hakyll/Web/CompressCss.hs
index 2df08fd..090fe10 100644
--- a/src/Hakyll/Web/CompressCss.hs
+++ b/src/Hakyll/Web/CompressCss.hs
@@ -11,7 +11,7 @@ import Data.List (isPrefixOf)
 import Control.Arrow ((>>^))
 
 import Hakyll.Core.Compiler
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
 import Hakyll.Core.Util.String
 
 -- | Compiler form of 'compressCss'
diff --git a/src/Hakyll/Web/Page.hs b/src/Hakyll/Web/Page.hs
index c41647b..5146bdc 100644
--- a/src/Hakyll/Web/Page.hs
+++ b/src/Hakyll/Web/Page.hs
@@ -67,7 +67,7 @@ import Data.Ord (comparing)
 
 import Hakyll.Core.Identifier
 import Hakyll.Core.Compiler
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
 import Hakyll.Web.Page.Internal
 import Hakyll.Web.Page.Read
 import Hakyll.Web.Page.Metadata
diff --git a/src/Hakyll/Web/Tags.hs b/src/Hakyll/Web/Tags.hs
index 328ae8b..32076a0 100644
--- a/src/Hakyll/Web/Tags.hs
+++ b/src/Hakyll/Web/Tags.hs
@@ -32,6 +32,7 @@ module Hakyll.Web.Tags
     , readTags
     , readCategory
     , renderTagCloud
+    , renderTagList
     , renderTagsField
     , renderCategoryField
     ) where
@@ -39,9 +40,8 @@ module Hakyll.Web.Tags
 import Prelude hiding (id)
 import Control.Category (id)
 import Control.Applicative ((<$>))
-import Data.Map (Map)
 import qualified Data.Map as M
-import Data.List (intersperse)
+import Data.List (intersperse, intercalate)
 import Control.Arrow (arr, (&&&), (>>>), (***), (<<^), returnA)
 import Data.Maybe (catMaybes, fromMaybe)
 import Data.Monoid (mconcat)
@@ -64,7 +64,7 @@ import Hakyll.Core.Util.String
 -- | Data about tags
 --
 data Tags a = Tags
-    { tagsMap :: Map String [Page a]
+    { tagsMap :: [(String, [Page a])]
     } deriving (Show, Typeable)
 
 instance Binary a => Binary (Tags a) where
@@ -90,7 +90,8 @@ readTagsWith :: (Page a -> [String])  -- ^ Function extracting tags from a page
              -> [Page a]              -- ^ Pages
              -> Tags a                -- ^ Resulting tags
 readTagsWith f pages = Tags
-    { tagsMap = foldl (M.unionWith (++)) M.empty (map readTagsWith' pages)
+    { tagsMap = M.toList $
+        foldl (M.unionWith (++)) M.empty (map readTagsWith' pages)
     }
   where
     -- Create a tag map for one page
@@ -108,41 +109,64 @@ readTags = readTagsWith getTags
 readCategory :: [Page a] -> Tags a
 readCategory = readTagsWith getCategory
 
--- | Render a tag cloud in HTML
+-- | Render tags in HTML
 --
-renderTagCloud :: (String -> Identifier)    -- ^ Produce a link for a tag
-               -> Double                    -- ^ Smallest font size, in percent
-               -> Double                    -- ^ Biggest font size, in percent
-               -> Compiler (Tags a) String  -- ^ Tag cloud renderer
-renderTagCloud makeUrl minSize maxSize = proc (Tags tags) -> do
+renderTags :: (String -> Identifier)
+           -- ^ Produce a link
+           -> (String -> String -> Int -> Int -> Int -> String)
+           -- ^ Produce a tag item: tag, url, count, min count, max count
+           -> ([String] -> String)
+           -- ^ Join items
+           -> Compiler (Tags a) String
+           -- ^ Tag cloud renderer
+renderTags makeUrl makeItem concatItems = proc (Tags tags) -> do
     -- In tags' we create a list: [((tag, route), count)]
     tags' <- mapCompiler ((id &&& (getRouteFor <<^ makeUrl)) *** arr length)
-                -< M.toList tags
+                -< tags
 
     let -- Absolute frequencies of the pages
         freqs = map snd tags'
 
-        -- Find out the relative count of a tag: on a scale from 0 to 1
-        relative count = (fromIntegral count - min') / (1 + max' - min')
-
-        -- Show the relative size of one 'count' in percent
-        size count =
-            let size' = floor $ minSize + relative count * (maxSize - minSize)
-            in show (size' :: Int) ++ "%"
-
-        -- The minimum and maximum count found, as doubles
+        -- The minimum and maximum count found
         (min', max')
             | null freqs = (0, 1)
-            | otherwise = (minimum &&& maximum) $ map fromIntegral freqs
+            | otherwise = (minimum &&& maximum) freqs
 
         -- Create a link for one item
-        makeLink ((tag, url), count) =
-            H.a ! A.style (toValue $ "font-size: " ++ size count)
-                ! A.href (toValue $ toUrl $ fromMaybe "/" url)
-                $ toHtml tag
+        makeItem' ((tag, url), count) =
+            makeItem tag (toUrl $ fromMaybe "/" url) count min' max'
 
     -- Render and return the HTML
-    returnA -< renderHtml $ mconcat $ intersperse " " $ map makeLink tags'
+    returnA -< concatItems $ map makeItem' tags'
+
+-- | Render a tag cloud in HTML
+--
+renderTagCloud :: (String -> Identifier)    -- ^ Produce a link for a tag
+               -> Double                    -- ^ Smallest font size, in percent
+               -> Double                    -- ^ Biggest font size, in percent
+               -> Compiler (Tags a) String  -- ^ Tag cloud renderer
+renderTagCloud makeUrl minSize maxSize =
+    renderTags makeUrl makeLink (intercalate " ")
+  where
+    makeLink tag url count min' max' = renderHtml $
+        H.a ! A.style (toValue $ "font-size: " ++ size count min' max')
+            ! A.href (toValue url)
+            $ toHtml tag
+
+    -- Show the relative size of one 'count' in percent
+    size count min' max' =
+        let diff = 1 + fromIntegral max' - fromIntegral min'
+            relative = (fromIntegral count - fromIntegral min') / diff
+            size' = floor $ minSize + relative * (maxSize - minSize)
+        in show (size' :: Int) ++ "%"
+
+-- | Render a simple tag list in HTML, with the tag count next to the item
+--
+renderTagList :: (String -> Identifier) -> Compiler (Tags a) (String)
+renderTagList makeUrl = renderTags makeUrl makeLink (intercalate ", ")
+  where
+    makeLink tag url count _ _ = renderHtml $
+        H.a ! A.href (toValue url) $ toHtml (tag ++ "(" ++ show count ++ ")")
 
 -- | Render tags with links
 --
@@ -151,14 +175,14 @@ renderTagsFieldWith :: (Page a -> [String])        -- ^ Function to get the tags
                     -> (String -> Identifier)      -- ^ Create a link for a tag
                     -> Compiler (Page a) (Page a)  -- ^ Resulting compiler
 renderTagsFieldWith tags destination makeUrl =
-    id &&& arr tags >>> setFieldA destination renderTags
+    id &&& arr tags >>> setFieldA destination renderTags'
   where
     -- Compiler creating a comma-separated HTML string for a list of tags
-    renderTags :: Compiler [String] String
-    renderTags =   arr (map $ id &&& makeUrl)
-               >>> mapCompiler (id *** getRouteFor)
-               >>> arr (map $ uncurry renderLink)
-               >>> arr (renderHtml . mconcat . intersperse ", " . catMaybes)
+    renderTags' :: Compiler [String] String
+    renderTags' =   arr (map $ id &&& makeUrl)
+                >>> mapCompiler (id *** getRouteFor)
+                >>> arr (map $ uncurry renderLink)
+                >>> arr (renderHtml . mconcat . intersperse ", " . catMaybes)
 
     -- Render one tag link
     renderLink _   Nothing         = Nothing
diff --git a/src/Hakyll/Web/Template.hs b/src/Hakyll/Web/Template.hs
index 9c49278..33e7a9b 100644
--- a/src/Hakyll/Web/Template.hs
+++ b/src/Hakyll/Web/Template.hs
@@ -59,7 +59,7 @@ import Text.Hamlet (HamletSettings, defaultHamletSettings)
 
 import Hakyll.Core.Compiler
 import Hakyll.Core.Identifier
-import Hakyll.Core.ResourceProvider
+import Hakyll.Core.Resource
 import Hakyll.Web.Template.Internal
 import Hakyll.Web.Template.Read
 import Hakyll.Web.Page.Internal