71 lines
2 KiB
Haskell
71 lines
2 KiB
Haskell
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-- | Internal rules module for types which are not exposed to the user
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--
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{-# LANGUAGE GeneralizedNewtypeDeriving #-}
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module Hakyll.Core.Rules.Internal
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( CompileRule (..)
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, RuleSet (..)
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, RuleState (..)
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, RulesM (..)
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, Rules
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, runRules
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) where
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import Control.Applicative (Applicative)
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import Control.Monad.Writer (WriterT, execWriterT)
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import Control.Monad.Reader (ReaderT, runReaderT)
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import Control.Monad.State (State, evalState)
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import Data.Monoid (Monoid, mempty, mappend)
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import Hakyll.Core.ResourceProvider
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import Hakyll.Core.Identifier
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import Hakyll.Core.Compiler.Internal
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import Hakyll.Core.Routes
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import Hakyll.Core.CompiledItem
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-- | Output of a compiler rule
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--
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-- * The compiler will produce a simple item. This is the most common case.
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--
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-- * The compiler will produce more compilers. These new compilers need to be
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-- added to the runtime if possible, since other items might depend upon them.
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--
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data CompileRule = CompileRule CompiledItem
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| MetaCompileRule [(Identifier, Compiler () CompileRule)]
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-- | A collection of rules for the compilation process
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--
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data RuleSet = RuleSet
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{ rulesRoutes :: Routes
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, rulesCompilers :: [(Identifier, Compiler () CompileRule)]
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}
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instance Monoid RuleSet where
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mempty = RuleSet mempty mempty
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mappend (RuleSet r1 c1) (RuleSet r2 c2) =
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RuleSet (mappend r1 r2) (mappend c1 c2)
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-- | Rule state
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--
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data RuleState = RuleState
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{ rulesMetaCompilerIndex :: Int
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} deriving (Show)
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-- | The monad used to compose rules
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--
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newtype RulesM a = RulesM
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{ unRulesM :: ReaderT ResourceProvider (WriterT RuleSet (State RuleState)) a
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} deriving (Monad, Functor, Applicative)
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-- | Simplification of the RulesM type; usually, it will not return any
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-- result.
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--
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type Rules = RulesM ()
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-- | Run a Rules monad, resulting in a 'RuleSet'
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--
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runRules :: Rules -> ResourceProvider -> RuleSet
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runRules rules provider =
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evalState (execWriterT $ runReaderT (unRulesM rules) provider) state
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where
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state = RuleState {rulesMetaCompilerIndex = 0}
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