main.hs

{-# LANGUAGE RecordWildCards #-}
import Control.Applicative ((<$>))
import Text.Parsec hiding (label)
import Text.Parsec.String
import Data.Either

data SemanticVersion
    = SemanticVersion
    { major :: Int
    , minor :: Int
    , patch :: Int
    , label :: Maybe String
    , meta  :: Maybe String
    } deriving (Eq, Read)

instance (Ord SemanticVersion) where
    (<) a b =
        or [ major a < major b
           , minor a < minor b
           , patch a < patch b
           , maybe 0 (const 1) (label a) < maybe 0 (const 1) (label b)
           ]
    (<=) a b =
        a == b || a < b
    (>) a b = not $ a <= b
    (>=) a b = a == b || a > b
    max a b = if a >= b then a else b
    min a b = if a <= b then a else b
    compare a b
        | a < b = LT
        | a > b = GT
        | otherwise = EQ

instance (Show SemanticVersion) where
    show (SemanticVersion {..}) =
        show major ++ "." ++
        show minor ++ "." ++
        show patch ++
        maybe "" ("-" ++) label ++
        maybe "" ("+" ++) meta


semVerP :: Parser SemanticVersion
semVerP = do
    maj <- parseInt
    char '.'
    min' <- parseInt
    char '.'
    pat <- parseInt
    lab <- optionMaybe (char '-' >> many1 alphaNum)
    met <- optionMaybe (char '+' >> many1 alphaNum)
    return $ SemanticVersion maj min' pat lab met
  where
    parseInt :: Parser Int
    parseInt = read <$> many1 digit

tests = rights $ map (parse semVerP "foobar")
    [ "2.0.11-alpha"
    , "0.1.7+amd64"
    , "0.10.7+20141005"
    , "2.0.12+i386"
    , "1.2.34"
    , "2.0.11+i386"
    , "20.1.1+i386"
    ]

main :: IO ()
main = undefined