module Dodge.Magnet where

import Control.Lens
import Dodge.Data.Bullet
import Dodge.Data.Magnet
import Geometry

dampField :: Magnet -> Bullet -> Bullet
dampField mg pt = case pt of
    Bullet{} | dist (_buPos pt) (_mgPos mg) < 100 -> pt & buVel *~ 0.5
    _ -> pt

curveLeftField :: Magnet -> Bullet -> Bullet
curveLeftField mg pt = case pt of
    Bullet{} | dist (_buPos pt) (_mgPos mg) < 500 -> pt & buVel %~ rotateV 0.2
    _ -> pt

curveAroundField :: Float -> Float -> Magnet -> Bullet -> Bullet
curveAroundField minrad maxrad mg pt = case pt of
    Bullet{} | thedist < maxrad -> pt & buVel %~ rotateToCircle
      where
        thedist = dist btpos mgpos
        mgpos = _mgPos mg
        btpos = _buPos pt
        rotateToCircle vel
            | (isLHS mgpos btpos (btpos +.+ vel) && isRHS mgpos btpos (mgpos +.+ vNormal vel))
                || (isRHS mgpos btpos (btpos +.+ vel) && isLHS mgpos btpos (mgpos +.+ vNormal vel)) =
                rotateV rot vel
            | otherwise = rotateV (negate rot) vel
        rot
            | thedist < minrad = 0.5
            | otherwise = 0.5 * ((maxrad - thedist) / (maxrad - minrad)) ** 2
    _ -> pt