module ParseFoldoc where

import Data.Char
import Data.Maybe
import System.Locale
import System.Time

data FoldocEntry = FoldocEntry String String [String] (Maybe CalendarTime) 

instance Show FoldocEntry where
    show (FoldocEntry h b s d) = 
	h ++ "\n" ++ unwords s ++ "\n\n" ++ b ++ "\n" 
	      ++ maybe "(no date)" showDate d ++ "\n"

showDate d = formatCalendarTime defaultTimeLocale fmt d
	where fmt = iso8601DateFormat Nothing

parse :: String -> [FoldocEntry]
parse s = map parseEntry (splitEntries (lines s))

parseEntry :: [String] -> FoldocEntry
parseEntry (h:"":b) = FoldocEntry h body (subjects body) maybeDate
    where b' = map dropTab (initIfLastEmpty b)
	  maybeDate = parseDate (last b')
	  b'' = take (length b' - 2) b'
	  body = unlines (if isJust maybeDate then b'' else b')

initIfLastEmpty :: [[a]] -> [[a]]
initIfLastEmpty [] = []
initIfLastEmpty [[]] = []
initIfLastEmpty (x:xs) = x:initIfLastEmpty xs

dropTab :: String -> String
dropTab ('\t':xs) = xs
dropTab xs = xs

subjects :: String -> [String]
subjects _ = []

{-
-- doesn't work
subjects :: String -> [String]
subjects [] = []
subjects ('<':xs) = (subj,'>':rs) = break (=='>') xs in subj : subjects rs
subjects (_:xs) = subjects xs
-}

parseDate :: String -> Maybe CalendarTime 
parseDate ('(':y1:y2:y3:y4:'-':m1:m2:'-':d1:d2:')':[]) = 
    Just $ CalendarTime { 
			 ctYear = read [y1,y2,y3,y4], 
			 ctMonth = toEnum (read [m1,m2] - 1),
			 ctDay = read [d1,d2],
			 ctHour = 0,
			 ctMin = 0,
			 ctSec = 0
			}
parseDate _ = Nothing

headIs :: Eq a => (a -> Bool) -> [a] -> Bool
headIs _ [] = False
headIs f (x:_) = f x

splitEntries :: [String] -- ^ list of lines
	     -> [[String]] -- ^ list of entries
splitEntries [] = []
splitEntries (l:ls) = let (e,r) = break (headIs (/='\t')) ls
			  in (l:e) : splitEntries r