import Text.ParserCombinators.Parsec
import qualified Text.ParserCombinators.Parsec.Token as Token
import Text.ParserCombinators.Parsec.Language (emptyDef)
import System.CPUTime
import System.Environment 

data Bounds = Bounds { minlat, maxlat, minlon, maxlon :: Double } deriving (Show)

update_lat lat bnd = Bounds { 
    minlat = min lat (minlat bnd),  maxlat = max lat (maxlat bnd),
    minlon = minlon bnd,  maxlon = maxlon bnd  }

update_lon lon bnd = Bounds { 
    minlat = minlat bnd,  maxlat = maxlat bnd,
    minlon = min lon (minlon bnd), maxlon = max lon (maxlon bnd) }

lexer = Token.makeTokenParser emptyDef
p_positive_float = Token.float lexer
p_float =  try (char '-' >> p_positive_float >>= return . negate) <|>  p_positive_float 

latlon name updater = do
  string (name ++ "=\"")
  f <- p_float
  char '"'
  updateState (updater f)  

p_param = do
  many1 letter
  string "=\""
  many $ noneOf "\""
  char '"'
  return ()
  
p_node_param =
  try (latlon "lat" update_lat) <|>
  try (latlon "lon" update_lon) <|>
  p_param
  
p_endnode = 
  try (string "/>") <|> manyTill anyChar (try (string "</node>"))
  
p_ws = many $ oneOf " \t\n"
  
p_node = do
  string "<node"
  many (p_ws >> p_node_param)
  p_endnode
  
p_tag = between (char '<') (char '>') (many (noneOf ">"))  
  
p_osm = do
  many $ (try p_node <|> p_tag) >> p_ws  
  bnd <- getState
  return $ show bnd

bnd0 = Bounds 1000.0 (-1000.0) 1000.0 (-1000.0)  

parse_osm_file fname = do
  input <- readFile fname
  case runParser p_osm bnd0 fname input of
      Right str  -> putStrLn str
      Left err -> do 
        putStr "parse error at "
        print err                    

main = do
  args <- getArgs
  case args of
    [] -> putStrLn "usage: bounds osmfile"
    fname:_ -> do
      t0 <- getCPUTime
      parse_osm_file fname
      t1 <- getCPUTime
      putStrLn $ show $ 1.0e-12 * (fromInteger $ t1 - t0)