module Diddo
( LogEntry(LogEntry)
, DiddoEntry(DiddoEntry)
, parseDiddoLogline
, formatDiddoEntry
, timestamp
, logToDiddoEntry
) where

import Data.DateTime( diffSeconds )
import Data.Maybe( fromMaybe )
import Data.Time.Clock( UTCTime(), NominalDiffTime(), diffUTCTime )
import Data.Time.Format( parseTime, formatTime )
import Data.Time.LocalTime( TimeZone() )
import Data.Time.LocalTime( ZonedTime(..), zonedTimeToUTC, utcToZonedTime )
import System.Locale
import qualified Data.Text as T

data LogEntry = LogEntry
    { timestamp     :: UTCTime
    , timezone      :: TimeZone
    , text          :: T.Text
    }

data DiddoEntry = DiddoEntry
    { startTime     :: ZonedTime
    , endTime       :: ZonedTime
    , comment       :: T.Text
    }

formatDiddoEntry :: String -> DiddoEntry -> T.Text
formatDiddoEntry format entry = T.intercalate (T.pack ";")
    [ T.pack $ formatTime defaultTimeLocale format (startTime entry)
    , T.pack $ formatTime defaultTimeLocale format (endTime entry)
    , T.pack $ diffTimeToHMSString $ diffUTCTime (zonedTimeToUTC (endTime entry)) (zonedTimeToUTC (startTime entry))
    , comment entry
    ]

logToDiddoEntry :: UTCTime -> LogEntry -> DiddoEntry
logToDiddoEntry startutc logentry = DiddoEntry startZoned endZoned $ text logentry
    where
        startZoned = utcToZonedTime (timezone logentry) startutc
        endZoned = utcToZonedTime (timezone logentry) $ timestamp logentry

parseDiddoLogline :: T.Text -> LogEntry
parseDiddoLogline line = LogEntry ts tz string
    where
        splitLine           = T.splitOn (T.pack ";") line
        string              = T.intercalate (T.pack ";") $ tail splitLine
        time                = parseISOsecondsTime $ head splitLine
        (ts,tz)             = (zonedTimeToUTC time, zonedTimeZone time)

parseToZonedTime :: String -> String -> ZonedTime
parseToZonedTime format string = fromMaybe (error $ "Input data broken: " ++ string) $ parseTime defaultTimeLocale format string

parseISOsecondsTime :: T.Text -> ZonedTime
parseISOsecondsTime timestring = parseToZonedTime (iso8601DateFormat $ Just "%T%z") $ T.unpack timestring

diffTimeToHMSString :: NominalDiffTime -> String
diffTimeToHMSString delta = printf "%d:%02d:%02d" h m s
    where
        (mLeft, s) = floor delta `divMod` 60 :: (Int, Int)
        (h, m)     = mLeft `divMod` 60