115 lines
2.9 KiB
Haskell
115 lines
2.9 KiB
Haskell
{-|
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Module : SubFix.Internal
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Description : core functions for subfix
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Copyright : (C) Jonathan Lamothe
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License : GPL-3
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Maintainer : jonathan@jlamothe.net
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= IMPORTANT:
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THIS MODULE IS USED INTERNALLY AND MAY BE SUBJECT TO CHANGE WITHOUT
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NOTICE!
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or (at
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your option) any later version.
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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-}
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{-# LANGUAGE LambdaCase #-}
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module SubFix.Internal (decodeTime, encodeTime, timestamp) where
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import Control.Monad (when)
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import Control.Monad.Trans.State (StateT (..), get, put)
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import Data.Char (isDigit, ord)
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-- | Decodes a timestamp to a number of milliseconds and the unused
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-- input
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decodeTime
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:: String
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-- ^ The encoded timestamp
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-> Maybe (Integer, String)
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-- ^ The number of milliseconds and unused input (if available)
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decodeTime = runStateT $ do
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hours <- getNum 2
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dropChar ':'
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mins <- getNum 2
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dropChar ':'
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secs <- getNum 2
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dropChar ','
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ms <- getNum 3
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return $ timestamp hours mins secs ms
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-- | Encodes a timestamp from a number of milliseconds
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encodeTime :: Integer -> String
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encodeTime ms = let
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(s, ms') = ms `divMod` 1000
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(m, s') = s `divMod` 60
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(h, m') = m `divMod` 60
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in
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mkNum 2 h ++ ":" ++
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mkNum 2 m' ++ ":" ++
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mkNum 2 s' ++ "," ++
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mkNum 3 ms'
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-- | Converts hours, minutes, seconds and milliseconds into the total
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-- number of milliseconds
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timestamp
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:: Integer
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-- ^ Hours
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-> Integer
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-- ^ Minutes
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-> Integer
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-- ^ Seconds
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-> Integer
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-- ^ Milliseconds
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-> Integer
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timestamp h m s ms = let
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m' = h * 60 + m
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s' = m' * 60 + s
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in s' * 1000 + ms
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getNum :: MonadFail m => Int -> StateT String m Integer
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getNum = f 0 where
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f val digits
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| digits <= 0 = return val
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| otherwise = do
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digit <- nextDigit
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f (val * 10 + digit) (pred digits)
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dropChar :: MonadFail m => Char -> StateT String m ()
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dropChar expected = do
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ch <- nextChar
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when (ch /= expected) $
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fail "incorrect character"
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nextDigit :: MonadFail m => StateT String m Integer
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nextDigit = do
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ch <- nextChar
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if isDigit ch
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then return $ toInteger $ ord ch - ord '0'
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else fail "missing digit"
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nextChar :: MonadFail m => StateT String m Char
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nextChar = get >>= \case
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"" -> fail "no character available"
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(ch:str) -> do
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put str
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return ch
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mkNum :: Int -> Integer -> String
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mkNum digits val =
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reverse $ take digits $ reverse (show val) ++ repeat '0'
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--jl
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