refactor(users/glittershark): Rename to grfn r/2485

Rename my //users directory and all places that refer to glittershark to
grfn, including nix references and documentation.

This may require some extra attention inside of gerrit's database after
it lands to allow me to actually push things.

Change-Id: I4728b7ec2c60024392c1c1fa6e0d4a59b3e266fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2933
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Reviewed-by: glittershark <grfn@gws.fyi>

1 files changed, 178 insertions, 0 deletions

diff --git a/users/grfn/xanthous/src/Xanthous/Util/Graphics.hs b/users/grfn/xanthous/src/Xanthous/Util/Graphics.hs
new file mode 100644
index 000000000000..6ba63a2d8a3f
--- /dev/null
+++ b/users/grfn/xanthous/src/Xanthous/Util/Graphics.hs
@@ -0,0 +1,178 @@
+{-# LANGUAGE TemplateHaskell #-}
+-- | Graphics algorithms and utils for rendering things in 2D space
+--------------------------------------------------------------------------------
+module Xanthous.Util.Graphics
+  ( circle
+  , filledCircle
+  , line
+  , straightLine
+  , delaunay
+
+    -- * Debugging and testing tools
+  , renderBooleanGraphics
+  , showBooleanGraphics
+  ) where
+--------------------------------------------------------------------------------
+import           Xanthous.Prelude
+--------------------------------------------------------------------------------
+-- https://github.com/noinia/hgeometry/issues/28
+-- import qualified Algorithms.Geometry.DelaunayTriangulation.DivideAndConquer
+--               as Geometry
+import qualified Algorithms.Geometry.DelaunayTriangulation.Naive
+              as Geometry
+import qualified Algorithms.Geometry.DelaunayTriangulation.Types as Geometry
+import           Control.Monad.State (execState, State)
+import qualified Data.Geometry.Point as Geometry
+import           Data.Ext ((:+)(..))
+import           Data.List (unfoldr)
+import           Data.List.NonEmpty (NonEmpty((:|)))
+import qualified Data.List.NonEmpty as NE
+import           Data.Ix (Ix)
+import           Linear.V2
+--------------------------------------------------------------------------------
+
+
+-- | Generate a circle centered at the given point and with the given radius
+-- using the <midpoint circle algorithm
+-- https://en.wikipedia.org/wiki/Midpoint_circle_algorithm>.
+--
+-- Code taken from <https://rosettacode.org/wiki/Bitmap/Midpoint_circle_algorithm#Haskell>
+circle :: (Num i, Ord i)
+       => V2 i -- ^ center
+       -> i    -- ^ radius
+       -> [V2 i]
+circle (V2 x₀ y₀) radius
+  -- Four initial points, plus the generated points
+  = V2 x₀ (y₀ + radius)
+  : V2 x₀ (y₀ - radius)
+  : V2 (x₀ + radius) y₀
+  : V2 (x₀ - radius) y₀
+  : points
+    where
+      -- Creates the (x, y) octet offsets, then maps them to absolute points in all octets.
+      points = concatMap generatePoints $ unfoldr step initialValues
+
+      generatePoints (V2 x y)
+        = [ V2 (x₀ `xop` x') (y₀ `yop` y')
+          | (x', y') <- [(x, y), (y, x)]
+          , xop <- [(+), (-)]
+          , yop <- [(+), (-)]
+          ]
+
+      initialValues = (1 - radius, 1, (-2) * radius, 0, radius)
+
+      step (f, ddf_x, ddf_y, x, y)
+        | x >= y = Nothing
+        | otherwise = Just (V2 x' y', (f', ddf_x', ddf_y', x', y'))
+        where
+          (f', ddf_y', y') | f >= 0 = (f + ddf_y' + ddf_x', ddf_y + 2, y - 1)
+                           | otherwise = (f + ddf_x, ddf_y, y)
+          ddf_x' = ddf_x + 2
+          x' = x + 1
+
+
+data FillState i
+  = FillState
+  { _inCircle :: Bool
+  , _result :: NonEmpty (V2 i)
+  }
+makeLenses ''FillState
+
+runFillState :: NonEmpty (V2 i) -> State (FillState i) a -> [V2 i]
+runFillState circumference s
+  = toList
+  . view result
+  . execState s
+  $ FillState False circumference
+
+-- | Generate a *filled* circle centered at the given point and with the given
+-- radius by filling a circle generated with 'circle'
+filledCircle :: (Num i, Integral i, Ix i)
+             => V2 i -- ^ center
+             -> i    -- ^ radius
+             -> [V2 i]
+filledCircle center radius =
+  case NE.nonEmpty (circle center radius) of
+    Nothing -> []
+    Just circumference -> runFillState circumference $
+      -- the first and last lines of all circles are solid, so the whole "in the
+      -- circle, out of the circle" thing doesn't work... but that's fine since
+      -- we don't need to fill them. So just skip them
+      for_ [succ minX..pred maxX] $ \x ->
+        for_ [minY..maxY] $ \y -> do
+          let pt = V2 x y
+              next = V2 x $ succ y
+          whenM (use inCircle) $ result %= NE.cons pt
+
+          when (pt `elem` circumference && next `notElem` circumference)
+            $ inCircle %= not
+
+      where
+        (V2 minX minY, V2 maxX maxY) = minmaxes circumference
+
+-- | Draw a line between two points using Bresenham's line drawing algorithm
+--
+-- Code taken from <https://wiki.haskell.org/Bresenham%27s_line_drawing_algorithm>
+line :: (Num i, Ord i) => V2 i -> V2 i -> [V2 i]
+line pa@(V2 xa ya) pb@(V2 xb yb)
+  = (if maySwitch pa < maySwitch pb then id else reverse) points
+  where
+    points               = map maySwitch . unfoldr go $ (x₁, y₁, 0)
+    steep                = abs (yb - ya) > abs (xb - xa)
+    maySwitch            = if steep then view _yx else id
+    [V2 x₁ y₁, V2 x₂ y₂] = sort [maySwitch pa, maySwitch pb]
+    δx                   = x₂ - x₁
+    δy                   = abs (y₂ - y₁)
+    ystep                = if y₁ < y₂ then 1 else -1
+    go (xTemp, yTemp, err)
+      | xTemp > x₂ = Nothing
+      | otherwise  = Just ((V2 xTemp yTemp), (xTemp + 1, newY, newError))
+      where
+        tempError        = err + δy
+        (newY, newError) = if (2 * tempError) >= δx
+                           then (yTemp + ystep, tempError - δx)
+                           else (yTemp, tempError)
+{-# SPECIALIZE line :: V2 Int -> V2 Int -> [V2 Int] #-}
+{-# SPECIALIZE line :: V2 Word -> V2 Word -> [V2 Word] #-}
+
+straightLine :: (Num i, Ord i) => V2 i -> V2 i -> [V2 i]
+straightLine pa@(V2 xa _) pb@(V2 _ yb) = line pa midpoint ++ line midpoint pb
+  where midpoint = V2 xa yb
+
+
+delaunay
+  :: (Ord n, Fractional n)
+  => NonEmpty (V2 n, p)
+  -> [((V2 n, p), (V2 n, p))]
+delaunay
+  = map (over both fromPoint)
+  . Geometry.edgesAsPoints
+  . Geometry.delaunayTriangulation
+  . map toPoint
+  where
+    toPoint (V2 px py, pid) = Geometry.Point2 px py :+ pid
+    fromPoint (Geometry.Point2 px py :+ pid) = (V2 px py, pid)
+
+--------------------------------------------------------------------------------
+
+renderBooleanGraphics :: forall i. (Num i, Ord i, Enum i) => [V2 i] -> String
+renderBooleanGraphics [] = ""
+renderBooleanGraphics (pt : pts') = intercalate "\n" rows
+  where
+    rows = row <$> [minX..maxX]
+    row x = [minY..maxY] <&> \y -> if V2 x y `member` ptSet then 'X' else ' '
+    (V2 minX minY, V2 maxX maxY) = minmaxes pts
+    pts = pt :| pts'
+    ptSet :: Set (V2 i)
+    ptSet = setFromList $ toList pts
+
+showBooleanGraphics :: forall i. (Num i, Ord i, Enum i) => [V2 i] -> IO ()
+showBooleanGraphics = putStrLn . pack . renderBooleanGraphics
+
+minmaxes :: forall i. (Ord i) => NonEmpty (V2 i) -> (V2 i, V2 i)
+minmaxes xs =
+  ( V2 (minimum1Of (traverse1 . _x) xs)
+       (minimum1Of (traverse1 . _y) xs)
+  , V2 (maximum1Of (traverse1 . _x) xs)
+       (maximum1Of (traverse1 . _y) xs)
+  )