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|
--------------------------------------------------------------------------------
-- | Module containing the template data structure
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Hakyll.Web.Template.Internal
( Template (..)
, TemplateKey (..)
, TemplateExpr (..)
, TemplateElement (..)
, readTemplate
) where
--------------------------------------------------------------------------------
import Control.Applicative (pure, (<$), (<$>), (<*>), (<|>))
import Control.Monad (void)
import Data.Binary (Binary, get, getWord8, put, putWord8)
import Data.Typeable (Typeable)
import Data.List (intercalate)
import GHC.Exts (IsString (..))
import qualified Text.Parsec as P
import qualified Text.Parsec.String as P
--------------------------------------------------------------------------------
import Hakyll.Core.Util.Parser
import Hakyll.Core.Writable
--------------------------------------------------------------------------------
-- | Datatype used for template substitutions.
newtype Template = Template
{ unTemplate :: [TemplateElement]
} deriving (Show, Eq, Binary, Typeable)
--------------------------------------------------------------------------------
instance Writable Template where
-- Writing a template is impossible
write _ _ = return ()
--------------------------------------------------------------------------------
instance IsString Template where
fromString = readTemplate
--------------------------------------------------------------------------------
newtype TemplateKey = TemplateKey String
deriving (Binary, Show, Eq, Typeable)
--------------------------------------------------------------------------------
instance IsString TemplateKey where
fromString = TemplateKey
--------------------------------------------------------------------------------
-- | Elements of a template.
data TemplateElement
= Chunk String
| Expr TemplateExpr
| Escaped
| If TemplateExpr Template (Maybe Template) -- expr, then, else
| For TemplateExpr Template (Maybe Template) -- expr, body, separator
| Partial TemplateExpr -- filename
deriving (Show, Eq, Typeable)
--------------------------------------------------------------------------------
instance Binary TemplateElement where
put (Chunk string) = putWord8 0 >> put string
put (Expr e) = putWord8 1 >> put e
put (Escaped) = putWord8 2
put (If e t f ) = putWord8 3 >> put e >> put t >> put f
put (For e b s) = putWord8 4 >> put e >> put b >> put s
put (Partial e) = putWord8 5 >> put e
get = getWord8 >>= \tag -> case tag of
0 -> Chunk <$> get
1 -> Expr <$> get
2 -> pure Escaped
3 -> If <$> get <*> get <*> get
4 -> For <$> get <*> get <*> get
5 -> Partial <$> get
_ -> error $
"Hakyll.Web.Template.Internal: Error reading cached template"
--------------------------------------------------------------------------------
-- | Expression in a template
data TemplateExpr
= Ident TemplateKey
| Call TemplateKey [TemplateExpr]
| StringLiteral String
deriving (Eq, Typeable)
--------------------------------------------------------------------------------
instance Show TemplateExpr where
show (Ident (TemplateKey k)) = k
show (Call (TemplateKey k) as) =
k ++ "(" ++ intercalate ", " (map show as) ++ ")"
show (StringLiteral s) = show s
--------------------------------------------------------------------------------
instance Binary TemplateExpr where
put (Ident k) = putWord8 0 >> put k
put (Call k as) = putWord8 1 >> put k >> put as
put (StringLiteral s) = putWord8 2 >> put s
get = getWord8 >>= \tag -> case tag of
0 -> Ident <$> get
1 -> Call <$> get <*> get
2 -> StringLiteral <$> get
_ -> error $
"Hakyll.Web.Tamplte.Internal: Error reading cached template"
--------------------------------------------------------------------------------
readTemplate :: String -> Template
readTemplate input = case P.parse template "" input of
Left err -> error $ "Cannot parse template: " ++ show err
Right t -> t
--------------------------------------------------------------------------------
template :: P.Parser Template
template = Template <$>
(P.many $ chunk <|> escaped <|> conditional <|> for <|> partial <|> expr)
--------------------------------------------------------------------------------
chunk :: P.Parser TemplateElement
chunk = Chunk <$> (P.many1 $ P.noneOf "$")
--------------------------------------------------------------------------------
expr :: P.Parser TemplateElement
expr = P.try $ do
void $ P.char '$'
e <- expr'
void $ P.char '$'
return $ Expr e
--------------------------------------------------------------------------------
expr' :: P.Parser TemplateExpr
expr' = stringLiteral <|> call <|> ident
--------------------------------------------------------------------------------
escaped :: P.Parser TemplateElement
escaped = Escaped <$ (P.try $ P.string "$$")
--------------------------------------------------------------------------------
conditional :: P.Parser TemplateElement
conditional = P.try $ do
void $ P.string "$if("
e <- expr'
void $ P.string ")$"
thenBranch <- template
elseBranch <- P.optionMaybe $ P.try (P.string "$else$") >> template
void $ P.string "$endif$"
return $ If e thenBranch elseBranch
--------------------------------------------------------------------------------
for :: P.Parser TemplateElement
for = P.try $ do
void $ P.string "$for("
e <- expr'
void $ P.string ")$"
body <- template
sep <- P.optionMaybe $ P.try (P.string "$sep$") >> template
void $ P.string "$endfor$"
return $ For e body sep
--------------------------------------------------------------------------------
partial :: P.Parser TemplateElement
partial = P.try $ do
void $ P.string "$partial("
e <- expr'
void $ P.string ")$"
return $ Partial e
--------------------------------------------------------------------------------
ident :: P.Parser TemplateExpr
ident = P.try $ Ident <$> key
--------------------------------------------------------------------------------
call :: P.Parser TemplateExpr
call = P.try $ do
f <- key
void $ P.char '('
P.spaces
as <- P.sepBy expr' (P.spaces >> P.char ',' >> P.spaces)
P.spaces
void $ P.char ')'
return $ Call f as
--------------------------------------------------------------------------------
stringLiteral :: P.Parser TemplateExpr
stringLiteral = do
void $ P.char '\"'
str <- P.many $ do
x <- P.noneOf "\""
if x == '\\' then P.anyChar else return x
void $ P.char '\"'
return $ StringLiteral str
--------------------------------------------------------------------------------
key :: P.Parser TemplateKey
key = TemplateKey <$> metadataKey
|
