{-# LANGUAGE FlexibleContexts, GeneralizedNewtypeDeriving #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Xmobar.Parsers
-- Copyright   :  (c) Andrea Rossato
-- License     :  BSD-style (see LICENSE)
--
-- Maintainer  :  Andrea Rossato <andrea.rossato@unitn.it>
-- Stability   :  unstable
-- Portability :  unportable
--
-- Parsers needed for Xmobar, a text based status bar
--
-----------------------------------------------------------------------------

module Parsers
    ( parseString
    , parseTemplate
    , parseConfig
    ) where

import Config
import Runnable
import Commands

import Control.Monad.Writer(mapM_, ap, liftM, liftM2, MonadWriter, tell)
import Control.Applicative.Permutation(optAtom, runPermsSep)
import Control.Applicative(Applicative, (<*>), Alternative, empty, (<$), (<$>))
import qualified Control.Applicative

import Data.List(tails, find, inits)
import qualified Data.Map as Map
import Text.ParserCombinators.Parsec
import Text.ParserCombinators.Parsec.Perm

-- | Runs the string parser
parseString :: Config -> String -> IO [(String, String)]
parseString c s =
    case parse (stringParser (fgColor c)) "" s of
      Left  _ -> return [("Could not parse string: " ++ s, fgColor c)]
      Right x -> return (concat x)

-- | Gets the string and combines the needed parsers
stringParser :: String -> Parser [[(String, String)]]
stringParser c = manyTill (textParser c <|> colorParser) eof

-- | Parses a maximal string without color markup.
textParser :: String -> Parser [(String, String)]
textParser c = do s <- many1 $
                    noneOf "<" <|>
                    ( try $ notFollowedBy' (char '<')
                                           (string "fc=" <|> string "/fc>" ) )
                  return [(s, c)]

-- | Wrapper for notFollowedBy that returns the result of the first parser.
--   Also works around the issue that, at least in Parsec 3.0.0, notFollowedBy
--   accepts only parsers with return type Char.
notFollowedBy' :: Parser a -> Parser b -> Parser a
notFollowedBy' p e = do x <- p
                        notFollowedBy $ try (e >> return '*')
                        return x

-- | Parsers a string wrapped in a color specification.
colorParser :: Parser [(String, String)]
colorParser = do
  c <- between (string "<fc=") (string ">") colors
  s <- manyTill (textParser c <|> colorParser) (try $ string "</fc>")
  return (concat s)

-- | Parses a color specification (hex or named)
colors :: Parser String
colors = many1 (alphaNum <|> char ',' <|> char '#')

-- | Parses the output template string
templateStringParser :: Config -> Parser (String,String,String)
templateStringParser c = do
  s   <- allTillSep c
  com <- templateCommandParser c
  ss  <- allTillSep c
  return (com, s, ss)

-- | Parses the command part of the template string
templateCommandParser :: Config -> Parser String
templateCommandParser c =
  let chr = char . head . sepChar
  in  between (chr c) (chr c) (allTillSep c)

-- | Combines the template parsers
templateParser :: Config -> Parser [(String,String,String)]
templateParser = many . templateStringParser

-- | Actually runs the template parsers
parseTemplate :: Config -> String -> IO [(Runnable,String,String)]
parseTemplate c s =
    do str <- case parse (templateParser c) "" s of
                Left _  -> return [("","","")]
                Right x -> return x
       let cl = map alias (commands c)
           m  = Map.fromList $ zip cl (commands c)
       return $ combine c m str

-- | Given a finite "Map" and a parsed template produce the resulting
-- output string.
combine :: Config -> Map.Map String Runnable -> [(String, String, String)] -> [(Runnable,String,String)]
combine _ _ [] = []
combine c m ((ts,s,ss):xs) = (com, s, ss) : combine c m xs
    where com  = Map.findWithDefault dflt ts m
          dflt = Run $ Com ts [] [] 10

allTillSep :: Config -> Parser String
allTillSep = many . noneOf . sepChar

stripComments :: String -> String
stripComments = unlines . map (strip False) . lines
    where strip m ('-':'-':xs) = if m then "--" ++ strip m xs else ""
          strip m ('"':xs) = '"': strip (not m) xs
          strip m (x:xs) = x : strip m xs
          strip _ [] = []

-- | Parse the config, logging a list of fields that were missing and replaced
-- by the default definition.
parseConfig :: String -> Either ParseError (Config,[String])
parseConfig = runParser parseConf fields "Config" . stripComments
    where
      parseConf = parse $ do
        sepEndSpaces ["Config","{"]
        x <- unWrapParser perms
        wrapSkip (string "}")
        eof
        return x
      perms = runPermsSep (WrappedParser $ wrapSkip $ string ",") $ liftM9 Config
        <$> withDef font         "font"          strField
        <*> withDef bgColor      "bgColor"       strField
        <*> withDef fgColor      "fgColor"       strField
        <*> withDef position     "position"     (field readsToParsec)
        <*> withDef lowerOnStart "lowerOnStart" (field parseEnum    )
        <*> withDef commands     "commands"     (field readsToParsec)
        <*> withDef sepChar      "sepChar"       strField
        <*> withDef alignSep     "alignSep"      strField
        <*> withDef template     "template"      strField

      wrapSkip   x = many space >> x >>= \r -> many space >> return r
      sepEndSpc    = mapM_ (wrapSkip . try . string)
      fieldEnd     = many $ space <|> oneOf ",}"
      field  e n c = (,) (e defaultConfig) $
                     updateState (filter (/= n)) >> sepEndSpc [n,"="] >>
                     wrapSkip c >>= \r -> fieldEnd >> return r

      withDef ext name parser = optAtom (do tell [name]; return $ ext defaultConfig)
                                        (liftM return $ WrappedParser $ parser name)

      parseEnum = choice $ map (\x -> x <$ string (show x)) [minBound .. maxBound]

      strField name = flip field name $ between (char '"') (char '"') (many1 . satisfy $ (/= '"'))
      field cont name = sepEndSpaces [name,"="] >> cont