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{-
Copyright (C) 2009 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 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 @-@.
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.
-}
module Text.Pandoc.Templates (renderTemplate) where
import Text.ParserCombinators.Parsec
import Control.Monad (liftM)
-- | Renders a template
renderTemplate :: [(String,String)] -- ^ Assoc. list of values for variables
-> String -- ^ Template
-> String
renderTemplate vals templ =
case runParser (do x <- parseTemplate; eof; return x) vals "template" templ of
Left e -> show e
Right r -> concat r
reservedWords :: [String]
reservedWords = ["else","endif"]
parseTemplate :: GenParser Char [(String,String)] [String]
parseTemplate =
many $ plaintext <|> escapedDollar <|> conditional <|> variable
plaintext :: GenParser Char [(String,String)] String
plaintext = many1 $ satisfy (/='$')
escapedDollar :: GenParser Char [(String,String)] String
escapedDollar = try $ string "$$" >> return "$"
conditional :: GenParser Char [(String,String)] String
conditional = try $ do
string "$if("
id' <- ident
string ")$"
skipMany (oneOf " \t")
optional newline
ifContents <- liftM concat parseTemplate
elseContents <- option "" $ do try (string "$else$")
skipMany (oneOf " \t")
optional newline
liftM concat parseTemplate
string "$endif$"
skipMany (oneOf " \t")
optional newline
st <- getState
return $ case lookup id' st of
Just "" -> elseContents
Just _ -> ifContents
Nothing -> elseContents
ident :: GenParser Char [(String,String)] 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 [(String,String)] String
variable = try $ do
char '$'
id' <- ident
char '$'
st <- getState
return $ case lookup id' st of
Just val -> val
Nothing -> ""
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