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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.XHtml (primHtml, Html)
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 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 = primHtml
-- | 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 -> ""
|
