module Dodge.LinearShockwave.Draw where

import Data.Maybe
import Dodge.Data.LinearShockwave
import Geometry.Data
import Geometry.Vector
import ListHelp
import Picture

drawLinearShockwave :: LinearShockwave -> Picture
drawLinearShockwave lw =
    setLayer BloomLayer $
        setDepth 20 $
            fold $
                theArc
                    ++ [ lineCol $ zip (reverse lps) $ map (`withAlpha` white) [0, 0.05 ..]
                       , lineCol $ zip (reverse rps) $ map (`withAlpha` white) [0, 0.05 ..]
                       ]
  where
    -- drawing half a circle here is not perfect, a slightly smaller arc would fit
    -- better, but this depends upon the angle formed by the following lines, which
    -- is not fixed (it varies with speed and angle of last turn)
    theArc = maybeToList $ do
        (hp, hv) <- safeHead pvs
        r <- safeHead xs
        return $
            color (snd $ last lpairs) $
                uncurryV translate hp $
                    arc (argV hv - pi / 2) (argV hv + pi / 2) $ r * magV hv
    cols = map (`withAlpha` white) [0, 0.05 ..]
    lpairs = zip (reverse lps) cols
    pvs = _lwPoints lw
    t = _lwTimer lw
    xs = take t $ drop (20 - t) [1, 1.2 ..]
    lps = zipWith f pvs xs
    rps = zipWith g pvs xs
    f (p, v) x = p +.+ x *.* vNormal v
    g (p, v) x = p -.- x *.* vNormal v