Add screen pos to char rendering

donut-hs.cabal

@@ -10,6 +10,7 @@ build-type:          Simple
 executable donut-hs
   main-is:             Main.hs
   other-modules:       Data.Vector
-  build-depends:       base >=4.14 && <4.15
+  build-depends:       base >=4.14 && <4.15,
+                       terminal-size
   hs-source-dirs:      src
   default-language:    Haskell2010

src/Data/Vector.hs

@@ -1,13 +1,16 @@
 module Data.Vector 
-( Vector(Vector) ) where
+( Vector(..) ) where
 
 data Vector a = Vector a a a
     deriving (Show, Eq)
 
 instance (Num a) => Num (Vector a) where
   (Vector x1 y1 z1) + (Vector x2 y2 z2) = Vector (x1+x2) (y1+y2) (z1+z2)
-  (*) = undefined
+  (Vector x1 y1 z1) * (Vector x2 y2 z2) = Vector (x1*x2) (y1*y2) (z1*z2)
   abs = undefined
   signum = undefined
   fromInteger = undefined
   negate = undefined
+
+instance Functor Vector where
+  fmap f (Vector x y z) = Vector (f x) (f y) (f z)

src/Main.hs

@@ -1,22 +1,67 @@
 module Main where
 
 import Data.Vector
+import System.Console.Terminal.Size
 
-_r :: Float
-_r = 1.0
-_R :: Float
-_R = 2.0
+type ScreenPos = (Int, Int)
 
-drawCircle :: Vector Float -> [Vector Float]
-drawCircle center = map ((+) center . vradius) [0,0.1..2*pi] 
-  where 
+type Grid = [[Char]]
+
+k :: Float 
+k = 1
+
+-- | A torus is essentially a circle cloned around a central point;
+-- we thus define r as being the radius of the center,
+r :: Float
+r = 5
+-- and r' a being the distance between the center of the 
+-- circle and the central point of the torus.
+r' :: Float
+r' = 25
+
+-- | Generates every point of a circle of radius r and
+-- center c.
+generateCircle :: Vector Float -> [Vector Float]
+generateCircle c = map ((+) c . vradius) [0.0,0.05..2*pi] 
+  where
+    -- | Generates a vector corresponding to the
+    -- radius, rotated by the given angle theta.
+    -- It is centered at point (0,0,0); we need to add that
+    -- vector the vector c.
     vradius :: Float -> Vector Float
-    vradius theta = Vector (_r * cos theta) (_r * sin theta) 0
+    vradius theta = Vector (r * cos theta) (r * sin theta) 0
+
+-- | Projects a vector to a point on the screen
+project :: Vector Float -> ScreenPos
+project v@(Vector _ _ z) = pair . fmap (round . (* (k/z))) $ v
+  where pair (Vector x y _) = (x, y)
 
-render :: [[Char]]
-render = ["hello", "world"]
+-- | Creates our final render made out of char,
+-- based on screen coordinates that must get rendered.
+renderScreenCoordinates :: [ScreenPos] -> Grid
+renderScreenCoordinates coordinates = 
+  map (concatMap (\cell -> if mustRender cell then ".." else "  ")) gridCoordinates
+  where 
+    gridCoordinates :: [[ScreenPos]]
+    gridCoordinates = [ 
+      [ (x, y) | x <- take 40 [0..] ] 
+      | y <- take 24 [0..] ]
+
+    mustRender :: ScreenPos -> Bool
+    mustRender pos = pos `elem` coordinates
+
+-- | Starts the rendering process.
+render :: Window Int -> [[Char]]
+render win@(Window w h) = coordinates
+  where 
+    coordinates = renderScreenCoordinates $ map project $ generateCircle (Vector r' 5 1)
 
 main :: IO ()
 main = do
-  let screen = unlines render
+  window <- size
+  window <- case window of
+    Just a -> return a
+    Nothing -> return $ Window 80 24
+
+  let screen = unlines $ render window
   putStr screen