LogAnalysis.hs

{-# OPTIONS_GHC -Wall #-}

module LogAnalysis where

import Log

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-- Exercise 1
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readInt :: String -> Int
readInt str = read str :: Int

nthWord :: String -> Int -> String
nthWord str n = words str !! n

dropWords :: String -> Int -> String
dropWords str n = unwords $ drop n $ words str

readNthInt :: String -> Int -> Int
readNthInt str n = readInt $ nthWord str n

parseMessage :: String -> LogMessage
parseMessage s = case (nthWord s 0) of
    "E" -> LogMessage (Error (readNthInt s 1)) (readNthInt s 2) (dropWords s 3)
    "I" -> LogMessage Info (readNthInt s 1) (dropWords s 2)
    "W" -> LogMessage Warning (readNthInt s 1) (dropWords s 2)
    _ -> Unknown s

parse :: String -> [LogMessage]
parse text = map parseMessage $ lines text

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-- Exercise 2
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insert :: LogMessage -> MessageTree -> MessageTree
insert lm Leaf = Node Leaf lm Leaf
insert lm@(LogMessage _ ts _) (Node l (LogMessage type0 ts0 msg0) r)
    | ts > ts0 = Node l (LogMessage type0 ts0 msg0) (insert lm r)
    | otherwise = Node (insert lm l) (LogMessage type0 ts0 msg0) r
insert _ mt = mt

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-- Exercise 3
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build :: [LogMessage] -> MessageTree
build = foldl (\m l -> insert l m) Leaf

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-- Exercise 4
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inOrder :: MessageTree -> [LogMessage]
inOrder Leaf = []
inOrder (Node l lm r) = concat[(inOrder l), [lm], (inOrder r)]

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-- Exercise 5
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lm2str :: LogMessage -> String
lm2str (LogMessage _ _ msg) = msg
lm2str (Unknown msg) = msg

relevantError :: LogMessage -> Bool
relevantError (LogMessage (Error level) _ _) = (level >= 50)
relevantError _ = False

whatWentWrong :: [LogMessage] -> [String]
whatWentWrong lms = map lm2str $ filter relevantError lms

-- Test with:
-- :l LogAnalysis.hs
-- testWhatWentWrong parse whatWentWrong "sample.log"