haskell-hw03.hs

LogAnalysis.hs

-- Exercise 1

invalidInt :: MaybeInt -> Bool
invalidInt (ValidInt _) = False
invalidInt InvalidInt = True

maybeIntValue :: MaybeInt -> Int
maybeIntValue (ValidInt val) = val
maybeIntValue  InvalidInt = 0

parseError :: [String] -> MaybeLogMessage
parseError m@(_:e:time:tokens)
  | length(m) < 3 = InvalidLM (unwords m)
  | invalidInt errorLevel = InvalidLM (unwords m)
  | invalidInt timeStamp = InvalidLM (unwords m)
  | otherwise = ValidLM (LogMessage (Error (maybeIntValue errorLevel)) (maybeIntValue timeStamp) (unwords tokens))
  where
    errorLevel = readInt e
    timeStamp = readInt time
parseError m = InvalidLM (unwords m)

parseInfo :: [String] -> MaybeLogMessage
parseInfo m@(_:time:tokens)
  | length(m) < 2 = InvalidLM (unwords m)
  | invalidInt timeStamp = InvalidLM (unwords m)
  | otherwise = ValidLM (LogMessage Info (maybeIntValue timeStamp) (unwords tokens))
  where
    timeStamp = readInt time
parseInfo m = InvalidLM (unwords m)

parseWarning :: [String] -> MaybeLogMessage
parseWarning m@(_:time:tokens)
  | length(m) < 2 = InvalidLM (unwords m)
  | invalidInt timeStamp = InvalidLM (unwords m)
  | otherwise = ValidLM (LogMessage Warning (maybeIntValue timeStamp) (unwords tokens))
  where
    timeStamp = readInt time
parseWarning m = InvalidLM (unwords m)

parseMessage :: String -> MaybeLogMessage
parseMessage message
  = case tokens of
    [] -> InvalidLM message
    ("E":_) -> parseError tokens
    ("I":_) -> parseInfo tokens
    ("W":_) -> parseWarning tokens
    _ -> InvalidLM message
  where
    tokens = words message

-- Exercise 2

validMessage :: MaybeLogMessage -> Bool
validMessage (ValidLM _) = True
validMessage (InvalidLM _) = False

getMessage :: MaybeLogMessage -> LogMessage
getMessage (ValidLM lm) = lm

validMessagesOnly :: [MaybeLogMessage] -> [LogMessage]
validMessagesOnly messages = map getMessage (filter validMessage messages)

-- Exercise 3

parse :: String -> [LogMessage]
parse file = validMessagesOnly (map parseMessage (lines file))

-- Exercise 4

compareMsgs :: LogMessage -> LogMessage -> Ordering
compareMsgs (LogMessage _ t1 _) (LogMessage _ t2 _)
  | t1 < t2 = LT
  | t1 == t2 = EQ
  | otherwise = GT

-- Exercise 5

sortMessages :: [LogMessage] -> [LogMessage]
sortMessages messages = sortBy compareMsgs messages

-- Exercise 6

criticalError :: LogMessage -> Bool
criticalError (LogMessage (Error level) _ _)
  | level >= 50 = True
  | otherwise = False
criticalError (LogMessage _ _ _) = False

errorMessage :: LogMessage -> String
errorMessage (LogMessage _ _ message) = message

whatWentWrong :: [LogMessage] -> [String]
whatWentWrong messages = map errorMessage (sortMessages (filter criticalError messages))