{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE UnicodeSyntax #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Graphics.Rendering.Plot.Render.Plot.Data
-- Copyright   :  (c) A. V. H. McPhail 2010, 2013
-- License     :  BSD3
--
-- Maintainer  :  haskell.vivian.mcphail <at> gmail <dot> com
-- Stability   :  provisional
-- Portability :  portable
--
-- Rendering 'Figure's
--
-----------------------------------------------------------------------------

module Graphics.Rendering.Plot.Render.Plot.Data (
                                       -- * Rendering
                                       renderData
                                       ) where

-----------------------------------------------------------------------------

import Data.List(partition)
--import Prelude.Unicode

--import Foreign.Storable 
--import Foreign.Ptr

--import Data.Packed.Vector
--import Data.Packed.Matrix
--import Data.Packed()
import Numeric.LinearAlgebra

import qualified Data.Array.IArray as A
--import qualified Data.Array.MArray as M
import qualified Data.Array.Base as B

import Data.Word

import Data.Maybe 
import qualified Graphics.Rendering.Cairo as C
import qualified Graphics.Rendering.Cairo.Matrix as CM

import Control.Monad.Reader
import Control.Monad.State
import Control.Monad.Maybe

import Graphics.Rendering.Plot.Types

import Graphics.Rendering.Plot.Render.Types
import Graphics.Rendering.Plot.Render.Plot.Format
import Graphics.Rendering.Plot.Render.Plot.Glyph
--import Graphics.Rendering.Plot.Render.Plot.Annotation
import Graphics.Rendering.Plot.Defaults

import Prelude hiding(min,max,abs)
import qualified Prelude

-----------------------------------------------------------------------------

findMinIdx, findMaxIdx :: Vector Double -> Double -> Int -> Int -> Int
findMinIdx v x n max
    | n >= max       = error "findMinIdx: data not in range"
    | v @> n >= x    = n
    | otherwise     = findMinIdx v x (n+1) max

findMaxIdx v x n min
    | n < 0          = error "findMaxIdx: data not in range"
    | v @> n <= x     = n
    | otherwise      = findMaxIdx v x (n-1) min

-----------------------------------------------------------------------------

greySurfaceFromMatrix :: C.SurfaceData Int Word8 -> Surface -> Int -> Int -> Int -> IO ()
greySurfaceFromMatrix s m stride r' c' = do
  let r = rows m
      c = cols m
  let fm = flatten m
      mx = maxElement m
      mn = minElement m
  mapM_ (\ri -> mapM_ (\(rj,ci) -> do
     let mi = ((rj `div` r')*c) + (ci `div` c')
     let e = round . (* 255) . (/ (mx-mn)) . (\x -> x - mn) $ (fm @> mi)
     let si = (rj*stride) + ci
     B.unsafeWrite s si e) $ zip (repeat ri) [0..((c*c')-1)]) [0..((r*r')-1)]

----------------------------------------------------------------------------

zeroToOne :: Double -> Double
zeroToOne x
    | x == 0.0  = 1.0
    | otherwise = x

renderData :: Ranges -> BarSetting -> DataSeries -> Render ()
renderData _ _  (DS_Surf m) = do 
  (BoundingBox x y w h) <- get
  let r = rows m
      c = cols m
  cairo $ do
    C.save
    --C.setAntialias C.AntialiasNone
    let r'' = Prelude.min 4 ((round h) `div` r)
        c'' = Prelude.min 4 ((round w) `div` c)
        r' = if r'' < 1 then 1 else r''
        c' = if c'' < 1 then 1 else c''
    s <- liftIO $ C.createImageSurface C.FormatA8 (c*c') (r*r')
    p <- liftIO $ C.imageSurfaceGetPixels s
    C.surfaceFlush s
    stride <- liftIO $ C.imageSurfaceGetStride s
    liftIO $ greySurfaceFromMatrix p m stride r' c'
    C.surfaceMarkDirty s
    C.setSourceSurface s x y
    pa <- C.getSource
    pm <- liftIO $ C.patternGetMatrix pa
    let pm' = CM.scale ((fromIntegral (c*c'))/w) ((fromIntegral (r*r'))/h) pm
    liftIO $ C.patternSetMatrix pa pm'
    --C.patternSetFilter pa C.FilterBest
    C.rectangle x y w h --(fromIntegral c) (fromIntegral r)
    C.paint
    C.stroke
    C.restore
    return ()

renderData r bc ds = do
  let aos = case ds of
              (DS_Y         os') -> zip (repeat (AbsFunction id)) (A.elems os')
              (DS_1toN abs' os') -> zip (repeat abs')             (A.elems os') 
              (DS_1to1 aos')     -> A.elems aos'
              _                  -> error "renderData: DataSeries not handled"
  let (los,ups) = partition (\(_,DecSeries o _) -> isLower o) aos
  (BoundingBox x y w h) <- get
  let (xsc,xmin',xmax') = getRanges XAxis Lower r
  let (xmin,xmax) = if xsc == Log then (logBase 10 $ zeroToOne xmin',logBase 10 $ zeroToOne xmax') else (xmin',xmax')
  let xscale = w/(xmax-xmin) 
  cairo $ C.save
  let (yscl,yminl',ymaxl') = getRanges YAxis Lower r
  let (yminl,ymaxl) = if yscl == Log then (logBase 10 $ zeroToOne yminl',logBase 10 $ zeroToOne ymaxl') else (yminl',ymaxl')
  let yscalel = h/(ymaxl-yminl) 
  -- transform to data coordinates
  cairo $ do 
    C.translate x (y+h)
    --C.scale xscale yscalel
    C.translate (-xmin*xscale) (yminl*yscalel)
    flipVertical
  los' <- configureBars xsc yscl xmin xmax xscale yscalel bc los 
  mapM_ (renderSeries xsc yscl xmin xmax xscale yscalel) los'
  cairo $ C.restore
  when (not $ null ups)
           (do
             cairo $ C.save
             let (yscu,yminu',ymaxu') = getRanges YAxis Upper r
             let (yminu,ymaxu) = if yscu == Log then (logBase 10 $ zeroToOne yminu',logBase 10 $ zeroToOne ymaxu') else (yminu',ymaxu')
             let yscaleu = h/(ymaxu-yminu) 
             -- transform to data coordinates
             cairo $ do 
               C.translate x (y+h)
               --C.scale xscale yscaleu
               C.translate (-xmin*xscale) (yminu*yscaleu)
               flipVertical
             ups' <- configureBars xsc yscu xmin xmax xscale yscaleu bc ups 
             mapM_ (renderSeries xsc yscu xmin xmax xscale yscaleu) ups'
             cairo $ C.restore)
             -- could filter annotations as well
  return ()

logSeries :: Scale -> Vector Double -> Vector Double
logSeries Log a = logBase 10 $ mapVector zeroToOne a
logSeries _   a = a

midpoints :: (Num (Vector t), Container Vector t) 
            => (t1, Vector t) -> (t1, Vector t)
midpoints(mi,v) = let v' = subVector 1 (dim v - 1) v
                      w' = subVector 0 (dim v - 1) v
                  in (mi,(v'+w')/2.0)

logSeriesMinMax :: Scale -> (Vector Double,Vector Double) -> (Vector Double,Vector Double)
logSeriesMinMax Log    (v,w) = (logSeries Log v,logSeries Log w)
logSeriesMinMax Linear x     = x

getBar :: (Integer,(Abscissae,DecoratedSeries)) 
        -> Maybe (Integer,(Abscissae,DecoratedSeries,BarType)) 
getBar (ix,(as,DecSeries os ds)) = let d = decorationGetBarType ds
   in case d of
        Just d' -> Just (ix,(as,DecSeries os ds,d'))
        Nothing -> Nothing

getBarWidth :: (Integer,(Abscissae,DecoratedSeries,BarType)) -> Render Double
getBarWidth (_,(_,_,(ColourBar _)))                  = do
  (BarOptions w _ _) <- asks (_baroptions . _renderoptions)
  return w
getBarWidth (_,(_,_,(TypeBar (BarOptions w _ _) _))) = return w

replace :: Integer -> a -> [a] -> [a]
replace n x xs = let (pre,post) = splitAt (fromIntegral n) xs
                 in pre ++ x:(tail post)

shiftAbscissa :: (Integer,(Abscissae,DecoratedSeries,BarType)) -> Double
              -> (Integer,(Abscissae,DecoratedSeries))
shiftAbscissa (i,(AbsFunction f,ds,_)) s  = (i,(AbsFunction ((+) s . f),ds))
shiftAbscissa (i,(AbsPoints mi t,ds,_)) s = (i,(AbsPoints mi (addConstant s t),ds))

replaceBars :: [(Integer,(Abscissae,DecoratedSeries))] 
            -> [(Abscissae,DecoratedSeries)] 
            -> [(Abscissae,DecoratedSeries)] 
replaceBars [] as = as
replaceBars ((i,ds):dss) as = replaceBars dss $ replace i ds as

scanStacked :: Vector Double
            -> (Integer,(Abscissae,DecoratedSeries,BarType))
            -> Vector Double
scanStacked v (i,(_,DecSeries (OrdPoints _ o _) _,_)) = v + (getOrdData o)

convertBarToCandle :: (Vector Double,Vector Double)
                   -> OrdSeries
                   -> OrdSeries
convertBarToCandle (v,w) os =
    case os of
      Plain _                 -> MinMax (v,w) Nothing
      Error _ (Right (el,eh)) -> MinMax (v,w) (Just (el,eh))
      _                       -> error "convertBarToCandle: unreachable code"

mkCandlesFromBars :: (Vector Double,Vector Double)
                  -> (Integer,(Abscissae,DecoratedSeries,BarType))
                  -> (Integer,(Abscissae,DecoratedSeries))
mkCandlesFromBars (v,w) (i,(a,DecSeries (OrdPoints ax o mb_l) _,bt)) = 
  (i,(a,DecSeries (OrdPoints ax ordSeries mb_l) (DecCand bt)))
      where
        ordSeries = convertBarToCandle (v,w) o

getOrdData' :: DecoratedSeries -> Series
getOrdData' (DecSeries (OrdPoints _ os _) _) = getOrdData os

configureBars :: Scale -> Scale
             -> Double -> Double -> Double -> Double
             -> BarSetting
             -> [(Abscissae,DecoratedSeries)] 
             -> Render [(Abscissae,DecoratedSeries)] 
configureBars xsc ysc xmin xmax xscale yscale bs aos = do
   let bars = mapMaybe getBar $ zip [0..] aos
   case bs of
     BarNone   -> return aos
     BarSpread -> do
        widths <- mapM getBarWidth bars
        let half_total = (sum widths) / 2
        let shifts' = init $ scanl (+) 0 widths
            shifts = map ((/ xscale) . flip (-) half_total) shifts'
        let shifted = zipWith shiftAbscissa bars shifts
        let aos' = replaceBars shifted aos
        return aos'
     BarStack  -> do
        let od = (getOrdData' . (\(_,b,_) -> b) . snd . head) bars
        let ln = dim $ od
        let zero = constant 0 ln
        let pairs = pair $ scanl scanStacked zero bars  
        let candles = zipWith mkCandlesFromBars pairs bars
        let aos' = replaceBars candles aos
        return aos'
            where pair [] = []
                  pair [x,y] = [(x,y)]
                  pair (x:y:xs) = (x,y) : pair (y:xs)

renderSeries :: Scale -> Scale 
             -> Double -> Double -> Double -> Double 
             -> (Abscissae,DecoratedSeries) -> Render ()
renderSeries xsc ysc xmin xmax xscale yscale (abs,(DecSeries o d)) = do
  dat  <- case o of
     (OrdFunction _ f _)            -> do
        (BoundingBox _ _ w _) <- get
        let t = logSeries xsc $ linspace (round w) (xmin,xmax)
        return $ Left $ Left ((True,t),logSeries ysc $ mapVector f t)
     (OrdPoints _ (Plain o') _)     -> do
        let t = case abs of
                  AbsFunction f    -> 
                    if isHist d
                    then (True,mapVector f $ fromList [0.0..(fromIntegral $ dim o')])
                    else (True,mapVector f $ fromList [1.0..(fromIntegral $ dim o')])
                  AbsPoints mi t'  -> (mi,t')
        return $ Left $ Left ((fst t,logSeries xsc $ snd t),logSeries ysc $ o')
     (OrdPoints _ (Error o' (Left e)) _) -> do
        let t = case abs of
                  AbsFunction f    -> 
                    if isHist d
                    then (True,mapVector f $ fromList [0.0..(fromIntegral $ dim o')])
                    else (True,mapVector f $ fromList [1.0..(fromIntegral $ dim o')])
                  AbsPoints mi t'  -> (mi,t')
        let t' = (fst t,logSeries xsc $ snd t)
        return $ Left $ Right $ Left ((t',logSeries ysc $ o'),(t',logSeries ysc $ e))
     (OrdPoints _ (Error o' (Right (l,h))) _) -> do
        let t = case abs of
                  AbsFunction f    -> 
                    if isHist d
                    then (True,mapVector f $ fromList [0.0..(fromIntegral $ dim o')])
                    else (True,mapVector f $ fromList [1.0..(fromIntegral $ dim o')])
                  AbsPoints mi t'  -> (mi,t') 
        let t' = (fst t,logSeries xsc $ snd t)
        return $ Left $ Right $ Right ((t',logSeries ysc $ o'),(t',logSeries ysc $ l),(t',logSeries ysc $ h))
     (OrdPoints _ (MinMax o' Nothing) _) -> do
        let t = case abs of
                  AbsFunction f    -> (True,mapVector f $ fromList [1.0..(fromIntegral $ dim $ fst o')])
                  AbsPoints mi t'  -> (mi,t')
        let t' = (fst t,logSeries xsc $ snd t)
        return $ Right $ Left (t',logSeriesMinMax ysc $ o')
     (OrdPoints _ (MinMax o' (Just (l,h))) _) -> do
        let t = case abs of
                  AbsFunction f    -> (True,mapVector f $ fromList [1.0..(fromIntegral $ dim l)])
                  AbsPoints mi t'  -> (mi,t')
        let t' = (fst t,logSeries xsc $ snd t)
        return $ Right $ Right ((t',logSeriesMinMax ysc o'),(t',(logSeries ysc l,logSeries ysc h)))
  case d of
    (DecLine lt)   -> do
        formatLineSeries lt
        case dat of
          Left (Left (t',y')) -> do
            renderSamples xscale yscale xmin xmax Nothing renderLineSample endLineSample t' y'
          _  -> error "Data.hs renderSeries: cannot have error bars with line type"
    (DecPoint pt)  -> do
        (pz,g) <- formatPointSeries pt
        case dat of
          Left (Left (t',y')) -> do
            renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz g) endPointSample t' y'
          Left (Right (Left ((t',y'),(_,e')))) -> do
            renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz g) endPointSample t' y'
            renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz Bot) endPointSample t' (y'-e')
            renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz Top) endPointSample t' (y'+e')
          Left (Right (Right ((t',y'),(_,l),(_,h)))) -> do
            renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz g) endPointSample t' y'
            renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz Bot) endPointSample t' l 
            renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz Top) endPointSample t' h 
          _  -> error "Data.hs renderSeries: cannot have MinMax data series with point type"
    (DecLinPt lt pt) -> do
       formatLineSeries lt
       (pz,g) <- formatPointSeries pt
       case dat of
         Left (Left (t',y')) -> do
           renderSamples xscale yscale xmin xmax Nothing renderLineSample endLineSample t' y'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz g) endPointSample t' y'
         Left (Right (Left ((t',y'),(_,e')))) -> do
           renderSamples xscale yscale xmin xmax Nothing renderLineSample endLineSample t' y'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz g) endPointSample t' y'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz Bot) endPointSample t' (y'-e')
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz Top) endPointSample t' (y'+e')
--               error "Data.hs renderSeries: cannot have single error value with line-points type"        
         Left (Right (Right ((t',y'),(_,l),(_,h)))) -> do
           renderSamples xscale yscale xmin xmax Nothing renderLineSample endLineSample t' y'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz g) endPointSample t' y'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz Bot) endPointSample t' l 
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample pz Top) endPointSample t' h 
         _  -> error "Data.hs renderSeries: cannot have MinMax data series with line-point type"
    (DecImpulse lt) -> do
       formatLineSeries lt
       case dat of
         Left (Left (t',y')) -> do
           renderSamples xscale yscale xmin xmax Nothing renderImpulseSample endImpulseSample t' y'
         _  -> error "Data.hs renderSeries: cannot have error bars with impulse type"
    (DecStep lt) -> do
        formatLineSeries lt
        case dat of
          Left (Left (t',y')) -> do
            renderSamples xscale yscale xmin xmax Nothing renderStepSample endStepSample t' y'
          _  -> error "Data.hs renderSeries: cannot have error bars with step type"
    (DecArea lt) -> do
       formatLineSeries lt
       case dat of
         Left (Left (t',y')) -> do
           let ln = dim $ snd t'
               xmin_ix = findMinIdx (snd t') xmin 0 (ln-1)
               x0 = (snd t') @> xmin_ix
               y0 = y' @> xmin_ix
           renderSamples xscale yscale xmin xmax Nothing renderAreaSample (endAreaSample x0 y0) t' y'
         _  -> error "Data.hs renderSeries: cannot have error bars with area type"
    (DecBar bt)   -> do
       (bw,bc,c) <- formatBarSeries bt
       (gw,_) <- formatPointSeries defaultPointType 
       case dat of
         Left (Left (t',y')) -> do
           renderSamples xscale yscale xmin xmax Nothing (renderBarSample bw bc c) endBarSample t' y' 
         Left (Right (Left ((t',y'),(_,e')))) -> do
           renderSamples xscale yscale xmin xmax Nothing (renderBarSample bw bc c) endBarSample t' y' 
           renderSamples xscale yscale xmin xmax Nothing (renderPointSampleUpDown gw) endPointSample t' e'
         Left (Right (Right ((t',y'),(_,l'),(_,h')))) -> do
           renderSamples xscale yscale xmin xmax Nothing (renderBarSample bw bc c) endBarSample t' y' 
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample gw Bot) endPointSample t' l'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample gw Top) endPointSample t' h'
         _  -> error "Data.hs renderSeries: cannot have MinMax data series with bar type"
    (DecHist bt)  -> do
       (bw,bc,c) <- formatBarSeries bt
       (gw,_) <- formatPointSeries defaultPointType 
       case dat of
         Left (Left (t',y')) -> do
           let ln = dim $ snd $ t'
               xmin_ix = findMinIdx (snd t') xmin 0 (ln-1)
               rest (m,v) = (m,subVector 1 (dim v - 1) v)
               x0 = (snd t') @> xmin_ix
               y0 = 0
           renderSamples xscale yscale xmin xmax (Just $ C.moveTo x0 y0) (renderHistSample bw bc c) endHistSample (rest t') y'
         Left (Right (Left ((t',y'),(_,e')))) -> do
           let ln = dim $ snd $ t'
               xmin_ix = findMinIdx (snd t') xmin 0 (ln-1)
               rest (m,v) = (m,subVector 1 (dim v - 1) v)
               x0 = (snd t') @> xmin_ix
               y0 = 0
           renderSamples xscale yscale xmin xmax (Just $ C.moveTo x0 y0) (renderHistSample bw bc c) endHistSample (rest t') y'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSampleUpDown gw) endPointSample (midpoints t') e'
         Left (Right (Right ((t',y'),(_,l'),(_,h')))) -> do
           let ln = dim $ snd $ t'
               xmin_ix = findMinIdx (snd t') xmin 0 (ln-1)
               rest (m,v) = (m,subVector 1 (dim v - 1) v)
               x0 = (snd t') @> xmin_ix
               y0 = 0
           renderSamples xscale yscale xmin xmax (Just $ C.moveTo x0 y0) (renderHistSample bw bc c) endHistSample (rest t') y'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample gw Bot) endPointSample (midpoints t') l'
           renderSamples xscale yscale xmin xmax Nothing (renderPointSample gw Top) endPointSample (midpoints t') h'
         _  -> error "Data.hs renderSeries: cannot have MinMax data series with histogram type"
    (DecCand bt)  → do
       (bw,bc,c) <- formatBarSeries bt
       case dat of 
         Left _ -> error "Candles series requires two data series (MinMax series)"
         Right (Left (t',y')) -> do
           renderMinMaxSamples xscale yscale xmin xmax Nothing (renderCandleSample bw bc c) endCandleSample t' y'
         Right (Right ((t',y'),(_,e'))) -> do
           renderMinMaxSamples xscale yscale xmin xmax Nothing (renderWhiskerSample bw bc c False) endWhiskerSample t' e'
           renderMinMaxSamples xscale yscale xmin xmax Nothing (renderCandleSample bw bc c) endCandleSample t' y'
    (DecWhisk bt)  → do
      (bw,bc,c) <- formatBarSeries bt
      case dat of 
        Left _ -> error "Candles series requires two data series (MinMax series)"
        Right (Left (t',y')) -> do
          renderMinMaxSamples xscale yscale xmin xmax Nothing (renderCandleSample bw bc c) endCandleSample t' y'
        Right (Right ((t',y'),(_,e'))) -> do
          renderMinMaxSamples xscale yscale xmin xmax Nothing (renderWhiskerSample bw bc c True) endWhiskerSample t' e'
          renderMinMaxSamples xscale yscale xmin xmax Nothing (renderCandleSample bw bc c) endCandleSample t' y'
  return ()

-----------------------------------------------------------------------------

renderSamples :: Double -> Double 
              -> Double -> Double 
              -> Maybe (C.Render ())
              -> (Double -> Double -> Double -> Double -> C.Render ()) -> (Double -> Double -> C.Render ())
              -> (Bool,Vector Double) -> Vector Double -> Render ()
renderSamples xscale yscale xmin xmax s f e (mono,t) y = do
  (BoundingBox _ _ w _) <- get
  let ln = dim t
      (xmin_ix,xmax_ix,num_pts) = if mono
                                  then (findMinIdx t xmin 0 (ln-1)
                                       ,findMaxIdx t xmax (ln-1) 0
                                       ,xmax_ix - xmin_ix + 1)
                                  else (0,ln-1,ln)
      diff'' = floor $ (fromIntegral num_pts)/w
      diff' = if diff'' <= 1 then 1 else diff''
      diff = if mono then diff' else 1
  cairo $ do
    case s of
      Nothing -> C.moveTo ((t @> xmin_ix)*xscale) ((y @> xmin_ix)*yscale)
      Just s' -> s'
    _ <- runMaybeT $ do
            mapVectorWithIndexM_ (\j y' -> do
               when (j >= xmin_ix && j `mod` diff == 0)
                        (renderSample j xmax_ix t (f xscale yscale) y')
               return ()) y
    (e xscale yscale)

-----------------------------------------------------------------------------

renderMinMaxSamples :: Double -> Double 
              -> Double -> Double 
              -> Maybe (C.Render ())
              -> (Double -> Double -> Double -> (Double,Double) -> C.Render ()) -> (Double -> Double -> C.Render ())
              -> (Bool,Vector Double) -> (Vector Double,Vector Double) -> Render ()
renderMinMaxSamples xscale yscale xmin xmax s f e (mono,t) y = do
  (BoundingBox _ _ w _) <- get
  let ln = dim t
      (xmin_ix,xmax_ix,num_pts) = if mono
                                  then (findMinIdx t xmin 0 (ln-1)
                                       ,findMaxIdx t xmax (ln-1) 0
                                       ,xmax_ix - xmin_ix + 1)
                                  else (0,ln-1,ln)
      diff'' = floor $ (fromIntegral num_pts)/w
      diff' = if diff'' <= 1 then 1 else diff''
      diff = if mono then diff' else 1
  cairo $ do
    case s of
      Nothing -> C.moveTo ((t @> xmin_ix)*xscale) (((fst $ y) @> xmin_ix)*yscale)
      Just s' -> s'
    _ <- runMaybeT $ mapVectorWithIndexM_ (\j t' -> do
        when (j >= xmin_ix && j `mod` diff == 0)
           (renderMinMaxSample j xmax_ix t' (f xscale yscale) (e xscale yscale) y)
        return ()) t
    return ()

-----------------------------------------------------------------------------

renderSample :: Int -> Int -> Vector Double 
             -> (Double -> Double -> C.Render ())
             -> Double -> MaybeT C.Render ()
renderSample ix xmax_ix t f y
    | ix >= xmax_ix            = do
                                lift $ f (t @> ix) y
                                fail "end of bounded area"
    | otherwise               = do
                                lift $ f (t @> ix) y

renderMinMaxSample :: Int -> Int -> Double 
             -> (Double -> (Double,Double) -> C.Render ()) -> C.Render () 
             -> (Vector Double,Vector Double) -> MaybeT C.Render ()
renderMinMaxSample ix xmax_ix t f e (yl,yu)
    | ix >= xmax_ix            = do
                                lift $ do
                                       f t (yl @> ix,yu @> ix)
                                       e
                                fail "end of bounded area"
    | otherwise               = do
                                lift $ f t (yl @> ix,yu @> ix)

-----------------------------------------------------------------------------

renderLineSample :: Double → Double -> Double -> Double -> C.Render ()
renderLineSample xscale yscale x y = C.lineTo (x*xscale) (y*yscale)

endLineSample :: Double -> Double -> C.Render ()
endLineSample _ _ = C.stroke

renderPointSample :: LineWidth -> Glyph -> Double -> Double -> Double -> Double -> C.Render ()
renderPointSample pz g xscale yscale x y = do
  C.moveTo (x*xscale) (y*yscale)
  renderGlyph pz g

renderPointSampleUpDown :: LineWidth -> Double -> Double -> Double -> Double -> C.Render ()
renderPointSampleUpDown pz xscale yscale x y = do
  C.moveTo (x*xscale) (y*yscale)
  renderGlyph pz (if y < 0 then Bot else Top)

endPointSample :: Double -> Double -> C.Render ()
endPointSample _ _ = return ()

renderImpulseSample :: Double -> Double -> Double -> Double -> C.Render ()
renderImpulseSample xscale yscale x y = do
  let x' = x*xscale
  C.moveTo x' 0
  C.lineTo x (y*yscale)
  C.stroke

endImpulseSample :: Double -> Double -> C.Render ()
endImpulseSample _ _ = return ()

renderStepSample :: Double -> Double -> Double -> Double -> C.Render ()
renderStepSample xscale yscale x y = do
  (x',_) <- C.getCurrentPoint
  let y' = y*yscale
  C.lineTo x'         y'
  C.lineTo (x*xscale) y'

endStepSample :: Double -> Double -> C.Render ()
endStepSample _ _ = C.stroke

renderAreaSample :: Double -> Double -> Double -> Double -> C.Render ()
renderAreaSample xscale yscale x y = C.lineTo (x*xscale) (y*yscale)

endAreaSample :: Double -> Double -> Double -> Double -> C.Render ()
endAreaSample x0 _ xscale _ = do
  (x',_) <- C.getCurrentPoint
  let x0' = x0*xscale
  C.lineTo x'  0
  C.lineTo x0' 0
  -- C.lineTo x0 y0
  C.closePath
  C.fill
  C.stroke

renderBarSample :: Width -> Color -> Color -> Double -> Double -> Double -> Double -> C.Render ()
renderBarSample bw c bc xscale yscale x y = do
  setColour bc
  C.rectangle ((x*xscale)-bw/2) 0 bw (y*yscale)
  C.strokePreserve
  setColour c
  C.fill
                                 
endBarSample :: Double -> Double -> C.Render ()
endBarSample _ _ = return ()

renderHistSample :: Width -> Color -> Color -> Double -> Double -> Double -> Double -> C.Render ()
renderHistSample _ c bc xscale yscale x y = do
  (x',_) <- C.getCurrentPoint
  let x'' = x*xscale
  C.stroke
  setColour bc
  C.rectangle x' 0 (x''-x') (y*yscale)
  C.strokePreserve
  setColour c
  C.fill
  C.moveTo x'' 0

endHistSample :: Double -> Double -> C.Render ()
endHistSample _ _ = return ()

renderCandleSample :: Width -> Color -> Color -> Double -> Double -> Double -> (Double,Double) -> C.Render ()
renderCandleSample bw c bc xscale yscale x (yl,yu) = do
  setColour bc
  let (yl',yu') = (yl*yscale,yu*yscale)
  C.rectangle ((x*xscale)-bw/2) yl' bw (yu'-yl')
  C.strokePreserve
  if (yl < yu)
     then do
       setColour c
     else do
       C.setSourceRGBA 1 1 1 1
  C.fill

endCandleSample :: Double -> Double -> C.Render ()
endCandleSample _ _ = return ()

renderWhiskerSample :: Width -> Color -> Color → Bool -> Double -> Double -> Double -> (Double,Double) -> C.Render ()
renderWhiskerSample bw _ bc whiskers xscale yscale x (yl,yu) = do
  setColour bc
  let (x',yl',yu') = (x*xscale,yl*yscale,yu*yscale)
  C.moveTo x' yl'
  C.lineTo x' yu'
  if whiskers
     then do
       C.moveTo (x'-bw/2) yu'
       C.lineTo (x'+bw/2) yu'
       C.moveTo (x'-bw/2) yl'
       C.lineTo (x'+bw/2) yl'
     else return ()
  C.stroke

endWhiskerSample :: Double -> Double -> C.Render ()
endWhiskerSample _ _ = return ()

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