{-# LANGUAGE FlexibleContexts #-}

module Network.IRC.Util where

import qualified Data.Text.Lazy          as LzT
import qualified Data.Text.Format        as TF

import ClassyPrelude
import Control.Arrow             (Arrow)
import Control.Concurrent.Lifted (Chan)
import Control.Monad.Base        (MonadBase)
import Data.Text                 (strip)
import Data.Time                 (diffUTCTime)

oneSec :: Int
oneSec = 1000000

type Latch = MVar ()

latchIt :: Latch -> IO ()
latchIt latch = putMVar latch ()

awaitLatch :: Latch -> IO ()
awaitLatch latch = void $ takeMVar latch

type Channel a = (Chan a, Latch)

mapKeys :: IsMap map => map -> [ContainerKey map]
mapKeys   = map fst . mapToList

mapValues :: IsMap map => map -> [MapValue map]
mapValues = map snd . mapToList

whenJust :: Monad m => Maybe t -> (t -> m ()) -> m ()
whenJust m f = maybe (return ()) f m

clean :: Text -> Text
clean = toLower . strip

io :: MonadIO m => IO a -> m a
io = liftIO

both :: Arrow cat => cat b d -> cat (b, b) (d, d)
both f = first f . second f

atomicModIORef :: MonadBase IO f => IORef t -> (t -> t) -> f ()
atomicModIORef ref f = void . atomicModifyIORef' ref $ \v -> (f v, v)

-- | Display a time span as one time relative to another.
relativeTime :: UTCTime -> UTCTime -> Text
relativeTime t1 t2 =
  maybe "unknown" (LzT.toStrict . format) $ find (\(s,_,_) -> abs period >= s) ranges
  where
    minute = 60; hour = minute * 60; day = hour * 24;
    week = day * 7; month = day * 30; year = month * 12

    format range =
      (if period > 0 then "in " else "")
      ++ case range of
          (_, str, 0)    -> pack str
          (_, str, base) -> TF.format (fromString str) $ TF.Only (abs $ round (period / base) :: Integer)
      ++ (if period <= 0 then " ago" else "")

    period = t1 `diffUTCTime` t2

    ranges = [(year*2,    "{} years",     year)
             ,(year,      "a year",       0)
             ,(month*2,   "{} months",    month)
             ,(month,     "a month",      0)
             ,(week*2,    "{} weeks",     week)
             ,(week,      "a week",       0)
             ,(day*2,     "{} days",      day)
             ,(day,       "a day",        0)
             ,(hour*4,    "{} hours",     hour)
             ,(hour*3,    "a few hours",  0)
             ,(hour*2,    "{} hours",     hour)
             ,(hour,      "an hour",      0)
             ,(minute*31, "{} minutes",   minute)
             ,(minute*30, "half an hour", 0)
             ,(minute*2,  "{} minutes",   minute)
             ,(minute,    "a minute",     0)
             ,(0,         "{} seconds",   1)
             ]