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-- | Internally used compiler module
--
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Hakyll.Core.Compiler.Internal
( Dependencies
, CompilerEnvironment (..)
, CompilerM (..)
, Compiler (..)
, runCompilerJob
, runCompilerDependencies
, fromJob
, fromDependencies
) where
import Prelude hiding ((.), id)
import Control.Applicative (Applicative, (<$>))
import Control.Monad.Reader (ReaderT, Reader, ask, runReaderT, runReader)
import Control.Monad ((<=<), liftM2)
import Data.Set (Set)
import qualified Data.Set as S
import Control.Category (Category, (.), id)
import Control.Arrow (Arrow, arr, first)
import Hakyll.Core.Identifier
import Hakyll.Core.CompiledItem
import Hakyll.Core.ResourceProvider
-- | A set of dependencies
--
type Dependencies = Set Identifier
-- | A lookup with which we can get dependencies
--
type DependencyLookup = Identifier -> CompiledItem
-- | Environment in which a compiler runs
--
data CompilerEnvironment = CompilerEnvironment
{ compilerIdentifier :: Identifier -- ^ Target identifier
, compilerResourceProvider :: ResourceProvider -- ^ Resource provider
, compilerDependencyLookup :: DependencyLookup -- ^ Dependency lookup
, compilerRoute :: Maybe FilePath -- ^ Site route
}
-- | The compiler monad
--
newtype CompilerM a = CompilerM
{ unCompilerM :: ReaderT CompilerEnvironment IO a
} deriving (Monad, Functor, Applicative)
-- | The compiler arrow
--
data Compiler a b = Compiler
{ compilerDependencies :: Reader ResourceProvider Dependencies
, compilerJob :: a -> CompilerM b
}
instance Category Compiler where
id = Compiler (return S.empty) return
(Compiler d1 j1) . (Compiler d2 j2) =
Compiler (liftM2 S.union d1 d2) (j1 <=< j2)
instance Arrow Compiler where
arr f = Compiler (return S.empty) (return . f)
first (Compiler d j) = Compiler d $ \(x, y) -> do
x' <- j x
return (x', y)
-- | Run a compiler, yielding the resulting target and it's dependencies
--
runCompilerJob :: Compiler () a -- ^ Compiler to run
-> Identifier -- ^ Target identifier
-> ResourceProvider -- ^ Resource provider
-> DependencyLookup -- ^ Dependency lookup table
-> Maybe FilePath -- ^ Route
-> IO a
runCompilerJob compiler identifier provider lookup' route =
runReaderT (unCompilerM $ compilerJob compiler ()) env
where
env = CompilerEnvironment
{ compilerIdentifier = identifier
, compilerResourceProvider = provider
, compilerDependencyLookup = lookup'
, compilerRoute = route
}
runCompilerDependencies :: Compiler () a
-> ResourceProvider
-> Dependencies
runCompilerDependencies compiler provider =
runReader (compilerDependencies compiler) provider
fromJob :: (a -> CompilerM b)
-> Compiler a b
fromJob = Compiler (return S.empty)
fromDependencies :: (ResourceProvider -> [Identifier])
-> Compiler b b
fromDependencies deps = Compiler (S.fromList . deps <$> ask) return
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