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|
-- | Internal rules module for types which are not exposed to the user
--
{-# LANGUAGE GeneralizedNewtypeDeriving, Rank2Types #-}
module Hakyll.Core.Rules.Internal
( CompileRule (..)
, RuleSet (..)
, RuleState (..)
, RuleEnvironment (..)
, RulesM (..)
, Rules
, runRules
) where
import Control.Applicative (Applicative)
import Control.Monad.Writer (WriterT, execWriterT)
import Control.Monad.Reader (ReaderT, runReaderT)
import Control.Monad.State (State, evalState)
import Data.Monoid (Monoid, mempty, mappend)
import Data.Set (Set)
import qualified Data.Map as M
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
-- | Output of a compiler rule
--
-- * The compiler will produce a simple item. This is the most common case.
--
-- * The compiler will produce more compilers. These new compilers need to be
-- added to the runtime if possible, since other items might depend upon them.
--
data CompileRule = CompileRule CompiledItem
| MetaCompileRule [(Identifier (), Compiler () CompileRule)]
-- | A collection of rules for the compilation process
--
data RuleSet = RuleSet
{ -- | Routes used in the compilation structure
rulesRoutes :: Routes
, -- | Compilation rules
rulesCompilers :: [(Identifier (), Compiler () CompileRule)]
, -- | A list of the used resources
rulesResources :: Set Resource
}
instance Monoid RuleSet where
mempty = RuleSet mempty mempty mempty
mappend (RuleSet r1 c1 s1) (RuleSet r2 c2 s2) =
RuleSet (mappend r1 r2) (mappend c1 c2) (mappend s1 s2)
-- | Rule state
--
data RuleState = RuleState
{ rulesNextIdentifier :: Int
} deriving (Show)
-- | Rule environment
--
data RuleEnvironment = RuleEnvironment
{ rulesResourceProvider :: ResourceProvider
, rulesPattern :: forall a. Pattern a
, rulesGroup :: Maybe String
}
-- | The monad used to compose rules
--
newtype RulesM a = RulesM
{ unRulesM :: ReaderT RuleEnvironment (WriterT RuleSet (State RuleState)) a
} deriving (Monad, Functor, Applicative)
-- | Simplification of the RulesM type; usually, it will not return any
-- result.
--
type Rules = RulesM ()
-- | Run a Rules monad, resulting in a 'RuleSet'
--
runRules :: RulesM a -> ResourceProvider -> RuleSet
runRules rules provider = nubCompilers $
evalState (execWriterT $ runReaderT (unRulesM rules) env) state
where
state = RuleState {rulesNextIdentifier = 0}
env = RuleEnvironment { rulesResourceProvider = provider
, rulesPattern = mempty
, rulesGroup = Nothing
}
-- | Remove duplicate compilers from the 'RuleSet'. When two compilers match an
-- item, we prefer the first one
--
nubCompilers :: RuleSet -> RuleSet
nubCompilers set = set { rulesCompilers = nubCompilers' (rulesCompilers set) }
where
nubCompilers' = M.toList . M.fromListWith (flip const)
|
