CircularArc.hs

module Graphics.CircularArc ( 
      CircularArc (..)
    , isClockwise
    , arcLength
) where
          
import Linear    
import Control.Lens

import Graphics.Curve

-- Would be enough one of these sets:
-- 1. c, r, startAngle, sweepAngle
-- 2. c, r, p1, p1, direction
data CircularArc = CircularArc { _c :: V2 Double
                               , _r :: Double
                               , _startAngle :: Double
                               , _sweepAngle :: Double
                               , _p1 :: V2 Double
                               , _p2 :: V2 Double
                               } deriving Show

instance Curve CircularArc where
    pointAt arc t = V2 x y
        where
            x = _c arc ^. _x + _r arc * cos (_startAngle arc + t * _sweepAngle arc)
            y = _c arc ^. _y + _r arc * sin (_startAngle arc + t * _sweepAngle arc)

isClockwise :: CircularArc -> Bool
isClockwise arc = _sweepAngle arc > 0
    
arcLength :: CircularArc -> Double
arcLength arc = _r arc * abs(_sweepAngle arc)