@@ -4,38 +4,56 @@ module Hakyll.Web.Template.Read
44 ( readTemplate
55 ) where
66
7−
87--------------------------------------------------------------------------------
9−import Data.List (isPrefixOf)
10−
8+import Control.Applicative ((<$>), (<$), (<*>))
9+import Control.Monad (void, mzero, guard)
10+import Text.Parsec
11+import Text.Parsec.String
1112
1213--------------------------------------------------------------------------------
1314import Hakyll.Web.Template.Internal
1415
15−
1616--------------------------------------------------------------------------------
17−-- | Construct a @Template@ from a string.
17+
1818readTemplate :: String -> Template
19−readTemplate = Template . readTemplate'
20− where
21− readTemplate' [] = []
22− readTemplate' string
23− | "$$" `isPrefixOf` string =
24− Escaped : readTemplate' (drop 2 string)
25− | "$" `isPrefixOf` string =
26− case readKey (drop 1 string) of
27− Just (key, rest) -> Key key : readTemplate' rest
28− Nothing -> Chunk "$" : readTemplate' (drop 1 string)
29− | otherwise =
30− let (chunk, rest) = break (== '$') string
31− in Chunk chunk : readTemplate' rest
32−
33− -- Parse an key into (key, rest) if it's valid, and return
34− -- Nothing otherwise
35− readKey string =
36− let (key, rest) = span validKeyChar string
37− in if not (null key) && "$" `isPrefixOf` rest
38− then Just (key, drop 1 rest)
39− else Nothing
40−
41− validKeyChar x = x `notElem` ['$', '\n', '\r']
19+readTemplate input =
20+ case parse template "" input of
21+ Left err -> error $ "Cannot parse template: " ++ show err
22+ Right t -> t
23+
24+template :: Parser Template
25+template = Template <$>
26+ (many1 $ chunk <|> escaped <|> conditional <|> key)
27+
28+chunk :: Parser TemplateElement
29+chunk = Chunk <$> (many1 $ noneOf "$")
30+
31+escaped :: Parser TemplateElement
32+escaped = Escaped <$ (try $ string "$$")
33+
34+conditional :: Parser TemplateElement
35+conditional = try $ do
36+ void $ string "$if("
37+ i <- ident
38+ void $ string ")$"
39+ thenBranch <- template
40+ elseBranch <- optionMaybe $ try (string "$else$") >> template
41+ void $ string "$endif$"
42+ return $ If i thenBranch elseBranch
43+
44+ident :: Parser String
45+ident = do
46+ i <- (:) <$> letter <*> (many $ alphaNum <|> oneOf " _-.")
47+ if i `elem` reserved
48+ then mzero
49+ else return i
50+
51+reserved :: [String]
52+reserved = ["if", "else","endif"]
53+
54+key :: Parser TemplateElement
55+key = try $ do
56+ void $ char '$'
57+ k <- ident
58+ void $ char '$'
59+ return $ Key k