# copied from KineticsKit - http://kineticskit.sourceforge.net/
# modified to remove it from visual
# May 2003

class Physics:
    """Mass Spring simulation
    """

    def __init__(self, timestep, oversample=1, gravity=None, viscosity=None):
        """Construct a system.
        """
        self.timestep = timestep
        self.rate = 1.0 / timestep
        self.oversample = oversample
        self.gravity = gravity
        self.viscosity = viscosity

        self.masses = []
        self.springs = []

        self.dragObject = None
        self.click = None
        self.distance = None

        self.rememberFixed = None
        self.rememberColor = None

    def insertMass(self, mass):
        """Insert mass into the system.
        """
        self.masses.append(mass)

    def insertMassList(self, masslist):
        """Insert all Masses in masslist into the system.
        """
        map(self.insertMass, masslist)

    def insertSpring(self, spring):
        """Insert spring into the system.
        """
        self.springs.append(spring)

    def insertSpringList(self, springlist):
        """Insert all Springs in springlist into the system.
        """
        map(self.insertSpring, springlist)

    def advance(self):
        """Perform one Iteration of the system by advancing one timestep.
        """
        microstep = self.timestep / self.oversample

        for i in range(self.oversample):
            for spring in self.springs:
                spring.calcSpringForce()
                if spring.damping:
                    spring.calcDampingForce()

            for mass in self.masses:
                if not mass.fixed:
                    if self.gravity:
                        mass.calcGravityForce(self.gravity)
                    if self.viscosity:
                        mass.calcViscosityForce(self.viscosity)
                    mass.calcNewLocation(microstep)
                mass.clearForce()

    def step(self):
        """Perform one step.  This is a convenience method.
        It actually calls dispatchDnD() and advance().
        """
        # self.dispatchDnD()
        self.advance()
        # visual.rate(self.rate) # best when placed after advance() and before dispatchDnD()

    def SetGravity(self, graveness):
        self.gravity = graveness        

    def SetViscosity(self, stiffness):
        self.viscosity = stiffness