-- SPDX-License-Identifier: ISC
-- Copyright (c) 2020 Camden Dixie O'Brien

module Main (main) where

import Graphics.Gloss
import Graphics.Gloss.Geometry.Angle

data PolarCoord = PolarCoord { radius :: Float, angle :: Float }

majorMass :: Float
majorMass = 10

minorMass :: Float
minorMass = 4

framesPerSecond :: Int
framesPerSecond = 120

angularVelocity :: Float
angularVelocity = pi

render :: PolarCoord -> Picture
render state = pictures [ circleSolid majorMass
                        , translatePolar state $ circleSolid minorMass ]

step :: a -> b -> PolarCoord -> PolarCoord
step _ _ state = let radiansPerFrame = angularVelocity / fromIntegral framesPerSecond
                     nextAngle = normalizeAngle $ angle state + radiansPerFrame
                 in state { angle = nextAngle }

translatePolar :: PolarCoord -> Picture -> Picture
translatePolar q = rotate (radToDeg $ angle q) . translate (radius q) 0

window :: Display
window = InWindow "Foo" (200, 200) (100, 100)

main :: IO ()
main = simulate window white framesPerSecond (PolarCoord 80 0) render step