Add IsString instance for Template

Closes #150

4 files changed, 94 insertions, 101 deletions

diff --git a/src/Hakyll/Web/Feed.hs b/src/Hakyll/Web/Feed.hs
index d394243..8c68a75 100644
--- a/src/Hakyll/Web/Feed.hs
+++ b/src/Hakyll/Web/Feed.hs
@@ -35,7 +35,6 @@ import           Hakyll.Core.Item
 import           Hakyll.Web.Template
 import           Hakyll.Web.Template.Context
 import           Hakyll.Web.Template.List
-import           Hakyll.Web.Template.Read
 
 
 --------------------------------------------------------------------------------
diff --git a/src/Hakyll/Web/Template.hs b/src/Hakyll/Web/Template.hs
index 56f5da9..086e9b2 100644
--- a/src/Hakyll/Web/Template.hs
+++ b/src/Hakyll/Web/Template.hs
@@ -122,6 +122,7 @@ module Hakyll.Web.Template
     , applyTemplate
     , loadAndApplyTemplate
     , applyAsTemplate
+    , readTemplate
     ) where
 
 
@@ -139,7 +140,6 @@ import           Hakyll.Core.Identifier
 import           Hakyll.Core.Item
 import           Hakyll.Web.Template.Context
 import           Hakyll.Web.Template.Internal
-import           Hakyll.Web.Template.Read
 
 
 --------------------------------------------------------------------------------
diff --git a/src/Hakyll/Web/Template/Internal.hs b/src/Hakyll/Web/Template/Internal.hs
index 138010e..4450a19 100644
--- a/src/Hakyll/Web/Template/Internal.hs
+++ b/src/Hakyll/Web/Template/Internal.hs
@@ -5,16 +5,22 @@
 module Hakyll.Web.Template.Internal
     ( Template (..)
     , TemplateElement (..)
+    , readTemplate
     ) where
 
 
 --------------------------------------------------------------------------------
-import           Control.Applicative  (pure, (<$>), (<*>))
-import           Data.Binary          (Binary, get, getWord8, put, putWord8)
-import           Data.Typeable        (Typeable)
+import           Control.Applicative     (pure, (<$), (<$>), (<*>), (<|>))
+import           Control.Monad           (void)
+import           Data.Binary             (Binary, get, getWord8, put, putWord8)
+import           Data.Typeable           (Typeable)
+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
 
 
@@ -46,10 +52,10 @@ data TemplateElement
 --------------------------------------------------------------------------------
 instance Binary TemplateElement where
     put (Chunk string) = putWord8 0 >> put string
-    put (Key key)      = putWord8 1 >> put key
+    put (Key k)        = putWord8 1 >> put k
     put (Escaped)      = putWord8 2
-    put (If key t f)   = putWord8 3 >> put key >> put t >> put f
-    put (For key b s)  = putWord8 4 >> put key >> put b >> put s
+    put (If k t f  )   = putWord8 3 >> put k >> put t >> put f
+    put (For k b s)    = putWord8 4 >> put k >> put b >> put s
     put (Partial p)    = putWord8 5 >> put p
 
     get = getWord8 >>= \tag -> case tag of
@@ -61,3 +67,84 @@ instance Binary TemplateElement where
         5 -> Partial <$> get
         _ -> error $
             "Hakyll.Web.Template.Internal: Error reading cached template"
+
+
+--------------------------------------------------------------------------------
+instance IsString Template where
+    fromString = readTemplate
+
+
+--------------------------------------------------------------------------------
+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.many1 $ chunk <|> escaped <|> conditional <|> for <|> partial <|> key)
+
+
+--------------------------------------------------------------------------------
+chunk :: P.Parser TemplateElement
+chunk = Chunk <$> (P.many1 $ P.noneOf "$")
+
+
+--------------------------------------------------------------------------------
+escaped :: P.Parser TemplateElement
+escaped = Escaped <$ (P.try $ P.string "$$")
+
+
+--------------------------------------------------------------------------------
+conditional :: P.Parser TemplateElement
+conditional = P.try $ do
+    void $ P.string "$if("
+    i <- metadataKey
+    void $ P.string ")$"
+    thenBranch <- template
+    elseBranch <- P.optionMaybe $ P.try (P.string "$else$") >> template
+    void $ P.string "$endif$"
+    return $ If i thenBranch elseBranch
+
+
+--------------------------------------------------------------------------------
+for :: P.Parser TemplateElement
+for = P.try $ do
+    void $ P.string "$for("
+    i <- metadataKey
+    void $ P.string ")$"
+    body <- template
+    sep  <- P.optionMaybe $ P.try (P.string "$sep$") >> template
+    void $ P.string "$endfor$"
+    return $ For i body sep
+
+
+--------------------------------------------------------------------------------
+partial :: P.Parser TemplateElement
+partial = P.try $ do
+    void $ P.string "$partial("
+    i <- stringLiteral
+    void $ P.string ")$"
+    return $ Partial i
+
+
+--------------------------------------------------------------------------------
+key :: P.Parser TemplateElement
+key = P.try $ do
+    void $ P.char '$'
+    k <- metadataKey
+    void $ P.char '$'
+    return $ Key k
+
+
+--------------------------------------------------------------------------------
+stringLiteral :: P.Parser String
+stringLiteral = do
+    void $ P.char '\"'
+    str <- P.many $ do
+        x <- P.noneOf "\""
+        if x == '\\' then P.anyChar else return x
+    void $ P.char '\"'
+    return str
diff --git a/src/Hakyll/Web/Template/Read.hs b/src/Hakyll/Web/Template/Read.hs
deleted file mode 100644
index 2421b2d..0000000
--- a/src/Hakyll/Web/Template/Read.hs
+++ /dev/null
@@ -1,93 +0,0 @@
---------------------------------------------------------------------------------
--- | Read templates in Hakyll's native format
-module Hakyll.Web.Template.Read
-    ( readTemplate
-    ) where
-
-
---------------------------------------------------------------------------------
-import           Control.Applicative          ((<$), (<$>))
-import           Control.Monad                (void)
-import           Text.Parsec
-import           Text.Parsec.String
-
-
---------------------------------------------------------------------------------
-import           Hakyll.Core.Util.Parser
-import           Hakyll.Web.Template.Internal
-
-
---------------------------------------------------------------------------------
-readTemplate :: String -> Template
-readTemplate input = case parse template "" input of
-    Left err -> error $ "Cannot parse template: " ++ show err
-    Right t  -> t
-
-
---------------------------------------------------------------------------------
-template :: Parser Template
-template = Template <$>
-    (many1 $ chunk <|> escaped <|> conditional <|> for <|> partial <|> key)
-
-
---------------------------------------------------------------------------------
-chunk :: Parser TemplateElement
-chunk = Chunk <$> (many1 $ noneOf "$")
-
-
---------------------------------------------------------------------------------
-escaped :: Parser TemplateElement
-escaped = Escaped <$ (try $ string "$$")
-
-
---------------------------------------------------------------------------------
-conditional :: Parser TemplateElement
-conditional = try $ do
-    void $ string "$if("
-    i <- metadataKey
-    void $ string ")$"
-    thenBranch <- template
-    elseBranch <- optionMaybe $ try (string "$else$") >> template
-    void $ string "$endif$"
-    return $ If i thenBranch elseBranch
-
-
---------------------------------------------------------------------------------
-for :: Parser TemplateElement
-for = try $ do
-    void $ string "$for("
-    i <- metadataKey
-    void $ string ")$"
-    body <- template
-    sep  <- optionMaybe $ try (string "$sep$") >> template
-    void $ string "$endfor$"
-    return $ For i body sep
-
-
---------------------------------------------------------------------------------
-partial :: Parser TemplateElement
-partial = try $ do
-    void $ string "$partial("
-    i <- stringLiteral
-    void $ string ")$"
-    return $ Partial i
-
-
---------------------------------------------------------------------------------
-key :: Parser TemplateElement
-key = try $ do
-    void $ char '$'
-    k <- metadataKey
-    void $ char '$'
-    return $ Key k
-
-
---------------------------------------------------------------------------------
-stringLiteral :: Parser String
-stringLiteral = do
-    void $ char '\"'
-    str <- many $ do
-        x <- noneOf "\""
-        if x == '\\' then anyChar else return x
-    void $ char '\"'
-    return str