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|
-- | This module provides a monadic DSL in which the user can specify the
-- different rules used to run the compilers
--
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Hakyll.Core.Rules
( RuleSet (..)
, RulesM
, Rules
, runRules
, compile
, create
, route
) where
import Control.Applicative (Applicative, (<$>))
import Control.Monad.Writer
import Control.Monad.Reader
import Hakyll.Core.ResourceProvider
import Hakyll.Core.Identifier
import Hakyll.Core.Identifier.Pattern
import Hakyll.Core.Compiler
import Hakyll.Core.Route
-- | A collection of rules for the compilation process
--
data RuleSet a = RuleSet
{ rulesRoute :: Route
, rulesCompilers :: [(Identifier, Compiler a)]
}
instance Monoid (RuleSet a) where
mempty = RuleSet mempty mempty
mappend (RuleSet r1 c1) (RuleSet r2 c2) =
RuleSet (mappend r1 r2) (mappend c1 c2)
-- | The monad used to compose rules
--
newtype RulesM a b = RulesM
{ unRulesM :: ReaderT ResourceProvider (Writer (RuleSet a)) b
} deriving (Monad, Functor, Applicative)
-- | Simplification of the RulesM type; usually, it will not return any
-- result.
--
type Rules a = RulesM a ()
-- | Run a Rules monad, resulting in a 'RuleSet'
--
runRules :: Rules a -> ResourceProvider -> RuleSet a
runRules rules provider = execWriter $ runReaderT (unRulesM rules) provider
-- | Add a route
--
addRoute :: Route -> Rules a
addRoute route' = RulesM $ tell $ RuleSet route' mempty
-- | Add a number of compilers
--
addCompilers :: [(Identifier, Compiler a)] -> Rules a
addCompilers compilers = RulesM $ tell $ RuleSet mempty compilers
-- | Add a compilation rule
--
-- This instructs all resources matching the given pattern to be compiled using
-- the given compiler
--
compile :: Pattern -> Compiler a -> Rules a
compile pattern compiler = RulesM $ do
identifiers <- matches pattern . resourceList <$> ask
unRulesM $ addCompilers $ zip identifiers (repeat compiler)
-- | Add a compilation rule
--
-- This sets a compiler for the given identifier
--
create :: Identifier -> Compiler a -> RulesM a ()
create identifier compiler = addCompilers [(identifier, compiler)]
-- | Add a route
--
route :: Pattern -> Route -> RulesM a ()
route pattern route' = addRoute $ ifMatch pattern route'
|
