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{-# LANGUAGE TypeSynonymInstances, FlexibleInstances #-}
{-
Copyright (C) 2009-2010 John MacFarlane <jgm@berkeley.edu>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-}
{- |
Module : Text.Pandoc.Templates
Copyright : Copyright (C) 2009-2010 John MacFarlane
License : GNU GPL, version 2 or above
Maintainer : John MacFarlane <jgm@berkeley.edu>
Stability : alpha
Portability : portable
A simple templating system with variable substitution and conditionals.
Example:
> renderTemplate [("name","Sam"),("salary","50,000")] $
> "Hi, $name$. $if(salary)$You make $$$salary$.$else$No salary data.$endif$"
> "Hi, John. You make $50,000."
A slot for an interpolated variable is a variable name surrounded
by dollar signs. To include a literal @$@ in your template, use
@$$@. Variable names must begin with a letter and can contain letters,
numbers, @_@, and @-@.
The value of a variable will be indented to the same level as the
variable.
A conditional begins with @$if(variable_name)$@ and ends with @$endif$@.
It may optionally contain an @$else$@ section. The if section is
used if @variable_name@ has a non-null value, otherwise the else section
is used.
Conditional keywords should not be indented, or unexpected spacing
problems may occur.
If a variable name is associated with multiple values in the association
list passed to 'renderTemplate', you may use the @$for$@ keyword to
iterate over them:
> renderTemplate [("name","Sam"),("name","Joe")] $
> "$for(name)$\nHi, $name$.\n$endfor$"
> "Hi, Sam.\nHi, Joe."
You may optionally specify separators using @$sep$@:
> renderTemplate [("name","Sam"),("name","Joe"),("name","Lynn")] $
> "Hi, $for(name)$$name$$sep$, $endfor$"
> "Hi, Sam, Joe, Lynn."
-}
module Text.Pandoc.Templates ( renderTemplate
, TemplateTarget
, getDefaultTemplate ) where
import Text.ParserCombinators.Parsec
import Control.Monad (liftM, when, forM)
import System.FilePath
import Data.List (intercalate, intersperse)
import Text.Blaze.Html (Html)
import Text.Blaze.Internal (preEscapedString)
import Data.ByteString.Lazy.UTF8 (ByteString, fromString)
import Text.Pandoc.Shared (readDataFile)
import qualified Control.Exception.Extensible as E (try, IOException)
-- | Get default template for the specified writer.
getDefaultTemplate :: (Maybe FilePath) -- ^ User data directory to search first
-> String -- ^ Name of writer
-> IO (Either E.IOException String)
getDefaultTemplate _ "native" = return $ Right ""
getDefaultTemplate _ "json" = return $ Right ""
getDefaultTemplate _ "docx" = return $ Right ""
getDefaultTemplate user "odt" = getDefaultTemplate user "opendocument"
getDefaultTemplate user "epub" = getDefaultTemplate user "html"
getDefaultTemplate user writer = do
let format = takeWhile (/='+') writer -- strip off "+lhs" if present
let fname = "templates" </> "default" <.> format
E.try $ readDataFile user fname
data TemplateState = TemplateState Int [(String,String)]
adjustPosition :: String -> GenParser Char TemplateState String
adjustPosition str = do
let lastline = takeWhile (/= '\n') $ reverse str
updateState $ \(TemplateState pos x) ->
if str == lastline
then TemplateState (pos + length lastline) x
else TemplateState (length lastline) x
return str
class TemplateTarget a where
toTarget :: String -> a
instance TemplateTarget String where
toTarget = id
instance TemplateTarget ByteString where
toTarget = fromString
instance TemplateTarget Html where
toTarget = preEscapedString
-- | Renders a template
renderTemplate :: TemplateTarget a
=> [(String,String)] -- ^ Assoc. list of values for variables
-> String -- ^ Template
-> a
renderTemplate vals templ =
case runParser (do x <- parseTemplate; eof; return x) (TemplateState 0 vals) "template" templ of
Left e -> error $ show e
Right r -> toTarget $ concat r
reservedWords :: [String]
reservedWords = ["else","endif","for","endfor","sep"]
parseTemplate :: GenParser Char TemplateState [String]
parseTemplate =
many $ (plaintext <|> escapedDollar <|> conditional <|> for <|> variable)
>>= adjustPosition
plaintext :: GenParser Char TemplateState String
plaintext = many1 $ noneOf "$"
escapedDollar :: GenParser Char TemplateState String
escapedDollar = try $ string "$$" >> return "$"
skipEndline :: GenParser Char st ()
skipEndline = try $ skipMany (oneOf " \t") >> newline >> return ()
conditional :: GenParser Char TemplateState String
conditional = try $ do
TemplateState pos vars <- getState
string "$if("
id' <- ident
string ")$"
-- if newline after the "if", then a newline after "endif" will be swallowed
multiline <- option False $ try $ skipEndline >> return True
ifContents <- liftM concat parseTemplate
-- reset state for else block
setState $ TemplateState pos vars
elseContents <- option "" $ do try (string "$else$")
when multiline $ optional skipEndline
liftM concat parseTemplate
string "$endif$"
when multiline $ optional skipEndline
let conditionSatisfied = case lookup id' vars of
Nothing -> False
Just "" -> False
Just _ -> True
return $ if conditionSatisfied
then ifContents
else elseContents
for :: GenParser Char TemplateState String
for = try $ do
TemplateState pos vars <- getState
string "$for("
id' <- ident
string ")$"
-- if newline after the "for", then a newline after "endfor" will be swallowed
multiline <- option False $ try $ skipEndline >> return True
let matches = filter (\(k,_) -> k == id') vars
let indent = replicate pos ' '
contents <- forM matches $ \m -> do
updateState $ \(TemplateState p v) -> TemplateState p (m:v)
raw <- liftM concat $ lookAhead parseTemplate
return $ intercalate ('\n':indent) $ lines $ raw ++ "\n"
parseTemplate
sep <- option "" $ do try (string "$sep$")
when multiline $ optional skipEndline
liftM concat parseTemplate
string "$endfor$"
when multiline $ optional skipEndline
setState $ TemplateState pos vars
return $ concat $ intersperse sep contents
ident :: GenParser Char TemplateState String
ident = do
first <- letter
rest <- many (alphaNum <|> oneOf "_-")
let id' = first : rest
if id' `elem` reservedWords
then pzero
else return id'
variable :: GenParser Char TemplateState String
variable = try $ do
char '$'
id' <- ident
char '$'
TemplateState pos vars <- getState
let indent = replicate pos ' '
return $ case lookup id' vars of
Just val -> intercalate ('\n' : indent) $ lines val
Nothing -> ""
|
