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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 @-@.
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.
-}
module Text.Pandoc.Templates (renderTemplate, getDefaultTemplate) where
import Text.ParserCombinators.Parsec
import Control.Monad (liftM, when)
import qualified Control.Exception as E (try, IOException)
import System.FilePath
import Text.Pandoc.Shared (readDataFile)
import Data.List (intercalate)
-- | Get the default template, either from the application's user data
-- directory (~/.pandoc on unix) or from the cabal data directory.
getDefaultTemplate :: String -> IO (Either E.IOException String)
getDefaultTemplate "native" = return $ Right ""
getDefaultTemplate "s5" = getDefaultTemplate "html"
getDefaultTemplate "odt" = getDefaultTemplate "opendocument"
getDefaultTemplate format = do
let format' = takeWhile (/='+') format -- strip off "+lhs" if present
E.try $ readDataFile $ "templates" </> format' <.> "template"
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
-- | 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) (TemplateState 0 vals) "template" templ of
Left e -> error $ show e
Right r -> concat r
reservedWords :: [String]
reservedWords = ["else","endif"]
parseTemplate :: GenParser Char TemplateState [String]
parseTemplate =
many $ (plaintext <|> escapedDollar <|> conditional <|> variable)
>>= adjustPosition
plaintext :: GenParser Char TemplateState String
plaintext = many1 $ noneOf "$"
escapedDollar :: GenParser Char TemplateState String
escapedDollar = try $ string "$$" >> return "$"
conditional :: GenParser Char TemplateState String
conditional = try $ do
let skipEndline = try $ skipMany (oneOf " \t") >> newline
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
let conditionSatisfied = case lookup id' vars of
Nothing -> False
Just "" -> False
Just _ -> True
contents <- if conditionSatisfied
then liftM concat parseTemplate
else do
parseTemplate -- skip if part, then reset position
setState $ TemplateState pos vars
option "" $ do try (string "$else$")
when multiline $ optional skipEndline
liftM concat parseTemplate
string "$endif$"
when multiline $ optional skipEndline
return 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 -> ""
|
