Log.hs

-- CIS 194 Homework 2

module Log where

import Control.Applicative

data MessageType = Info
| Warning
| Error Int
deriving (Show, Eq)

type TimeStamp = Int

data LogMessage = LogMessage MessageType TimeStamp String
| Unknown String
deriving (Show, Eq)

data MessageTree = Leaf
| Node MessageTree LogMessage MessageTree
deriving (Show, Eq)

-- | @testParse p n f@ tests the log file parser @p@ by running it
-- on the first @n@ lines of file @f@.
testParse :: (String -> [LogMessage])
-> Int
-> FilePath
-> IO [LogMessage]
testParse parse n file = take n . parse <$> readFile file

-- | @testWhatWentWrong p w f@ tests the log file parser @p@ and
-- warning message extractor @w@ by running them on the log file
-- @f@.
testWhatWentWrong :: (String -> [LogMessage])
-> ([LogMessage] -> [String])
-> FilePath
-> IO [String]
testWhatWentWrong parse whatWentWrong file
= whatWentWrong . parse <$> readFile file

LogAnalysis.hs

module LogAnalysis where
import Log

parseMessage :: String -> LogMessage
parseMessage s = LogMessage messageType timestamp message
                 where  wordAry       = words s
                        firstChar     = wordAry !! 0
                        secondChar    = wordAry !! 1
                        messageType   = case firstChar of
                                          "I" -> Info
                                          "W" -> Warning
                                          "E" -> (Error (read secondChar :: Int))
                        timestamp     = case messageType of
                                          (Error n) -> read (wordAry !! 2) :: Int
                                          (Info)    -> read (wordAry !! 1) :: Int
                                          (Warning) -> read (wordAry !! 1) :: Int
                        message       = case messageType of
                                          (Error n) -> unwords (drop 3 wordAry)
                                          (Info)    -> unwords (drop 2 wordAry)
                                          (Warning) -> unwords (drop 2 wordAry)