Haskell refactor, scale functions are made from minMax + period outside

blah.hs

-- old ----------------------------------------------------------------
mkGraphMeta (start,end) (aggregated,timeSeriesWithColor) =
  (aggregated,) $ fromMaybe (Nothing,[]) $ case second unTimeSeries <$> (timeSeriesWithColor :: [(String,TimeSeries)]) of
    []  -> Nothing
    xss -> do
      minMax@(vMin,vMax) <- getMinMax $ snd <$> (xss :: [(String,[(UTCTime,Double)])])
      let
        tw = end `diffUTCTime` start
        fx = fromIntegral pWidth / tw
        ph = fromIntegral pHeight
        fy = case vMax - vMin of
          0 -> 1
          h -> ph / h
        scalify (t,v) =
          let
            tx       = t `diffUTCTime` start
            x :: Int = floor $ tx * fx
            y        = ph - (v - vMin) * fy
          in (fromIntegral x,y)
        xss' = second (fmap scalify) <$> xss
      return (Just minMax, force xss')
-- new ----------------------------------------------------------------
mkGraphMeta xs (xScale,yScale) = second (fmap (xScale *** yScale) . coerce) <$> xs