import Common
import Control.Monad
import Data.Functor.Contravariant.Divisible
import Graphics.Luminance

main :: IO ()
main = startup $ \window loop -> do
  triangle <- createGeometry vertices Nothing Triangle
  vs <- createStage VertexShader vsSource
  fs <- createStage FragmentShader fsSource
  (program,colorOffsetU) <- createProgram [vs,fs] $ \uni -> do
    colorU <- uni (UniformName "color")
    offsetU <- uni (UniformName "offset")
    pure $ divided colorU offsetU
  loop $ do
    void . runCmd . draw $ framebufferBatch defaultFramebuffer
      [anySPBatch . shaderProgramBatch_ program $
        [
          renderCmd Nothing True colorOffsetU (color0,offset0) triangle 
        , renderCmd Nothing True colorOffsetU (color1,offset1) triangle 
        , renderCmd Nothing True colorOffsetU (color2,offset2) triangle 
        ]
      ]
    endFrame window

color0,color1,color2 :: (Float,Float,Float)
color0 = (1,0,0)
color1 = (0,1,0)
color2 = (0,0,1)

offset0,offset1,offset2 :: (Float,Float)
offset0 = (-0.25,0)
offset1 = (0.25,0)
offset2 = (0,0.25)

vertices :: [V 2 Float]
vertices =
  [
    vec2 (-0.5) (-0.5)
  , vec2 0 0.5
  , vec2 0.5 (-0.5)
  ]

vsSource :: String
vsSource = unlines
  [
    "in vec2 co;"

  , "uniform vec2 offset;"

  , "void main() {"
  , "  gl_Position = vec4(co + offset, 0., 1.);"
  , "}"
  ]

fsSource :: String
fsSource = unlines
  [
    "out vec4 frag;"

  , "uniform vec3 color;"

  , "void main() {"
  , "  frag = vec4(color, 1.);"
  , "}"
  ]