package AirPhysicsModule
import public Entity
import Interpolation

public constant MAX_MASS = 250
//Module for Physical Simulation
public module AirPhysicsModule
	/** Affected by gravity */
	boolean affectedByGravity = true

	real terrainZ = 0.

	// Physical factors

	// The higher the more slide. Should be < 1.
	real surfaceFriction = 0.9
	// Defines the bounciness
	real restitution = 0.9
	// The density of the object
	real mass = 10


	// This function should be called every ANIMATION_PERIOD tick if the Entity is active
	function physicsUpdate(Entity e)
		let pos = e.getPos()
		terrainZ = pos.getTerrainZ()
		if pos.z <= terrainZ + .2
			onGround(e)
		else
			inAir(e)

	// When the Entity is on or near the ground
	function onGround(Entity e)
		let pos = e.getPos()
		// If the Entity is moving towards
		let normal = pos.toVec2().getTerrainNormal(2.).norm()
		// Is the Entity going away from the ground?
		if e.getVel().dot(normal) > 0
			return

		vec3 pv = e.getVel().project(normal)
		pv *= (-1. - restitution)
		if pv.z > 4.
			e.addVel(pv)
		else
			e.scaleVel(surfaceFriction * bezier3(1,0.85,0,mass/MAX_MASS))


	function inAir(Entity e)
		let coef = bezier3(0.930,0.985,1,mass/MAX_MASS)
		let gcoef = bezier3(0.1,0.875,1,mass/MAX_MASS)
		if affectedByGravity
			e.addVel(vec3(0,0,e.gravity * gcoef))
		e.scaleVel(coef)