#!/usr/bin/env python3

from NucData import Masses
import numpy as np

class Nucleus:
	def __init__(self, z, a):
		self.Z = z
		self.A = a
		self.Symbol = Masses.GetSymbol(self.Z, self.A)
		self.GSMass = Masses.GetMass(self.Z, self.A)

	def Minus(self, rhs):
		final_Z = self.Z - rhs.Z
		final_A = self.A - rhs.A
		if final_A < 0 or final_Z < 0:
			print("Illegal minus operation on Nuclei!")
			return Nucleus(0,0)
		else:
			return Nucleus(final_Z, final_A)

	def Plus(self, rhs):
		return Nucleus(self.Z + rhs.Z, self.A + rhs.A)

class Reaction:
	DEG2RAD = np.pi/180.0 #degrees to radians
	C = 299792458 #speed of light m/s
	QBRHO2P = 1.0E-9*C #Converts qbrho to p (kG*cm -> MeV/c)
	DISP = 1.96 
	MAG = 0.39
	def __init__(self, zt, at, zp, ap, ze, ae, beamKE, theta, bfield):
		self.Target = Nucleus(zt, at)
		self.Projectile = Nucleus(zp, ap)
		self.Ejectile = Nucleus(ze, ae)
		self.Residual = (self.Target.Plus(self.Projectile)).Minus(self.Ejectile)
		self.BKE = beamKE
		self.Theta = theta * self.DEG2RAD
		self.Bfield = bfield
		self.Name = self.Target.Symbol +"("+ self.Projectile.Symbol +","+ self.Ejectile.Symbol +")"+ self.Residual.Symbol

	def GetEjectileKineticEnergy(self, Elevel) :
		Q = self.Target.GSMass + self.Projectile.GSMass - (self.Ejectile.GSMass + self.Residual.GSMass + Elevel)
		Ethresh = -Q*(self.Ejectile.GSMass+self.Residual.GSMass)/(self.Ejectile.GSMass + self.Residual.GSMass - self.Projectile.GSMass)
		if self.BKE < Ethresh:
			return 0.0
		term1 = np.sqrt(self.Projectile.GSMass*self.Ejectile.GSMass*self.BKE)/(self.Ejectile.GSMass + self.Residual.GSMass)*np.cos(self.Theta)
		term2 = (self.BKE*(self.Residual.GSMass - self.Projectile.GSMass) + self.Residual.GSMass*Q)/(self.Ejectile.GSMass + self.Residual.GSMass)
		ke1 = term1 + np.sqrt(term1**2.0 + term2)
		ke2 = term1 - np.sqrt(term1**2.0 + term2)

		if ke1 > 0:
			return ke1**2.0
		else :
			return ke2**2.0

	def GetFocalPlaneZOffset(self):
		ejectKE = self.GetEjectileKineticEnergy(0.0)
		ejectP = np.sqrt(ejectKE**2.0 + 2.0*ejectKE*self.Ejectile.GSMass)
		rho = ejectP/(self.QBRHO2P*self.Bfield*self.Ejectile.Z)
		K = np.sqrt(self.Projectile.GSMass*self.Ejectile.GSMass*self.BKE/ejectKE)*np.sin(self.Theta)
		K /= self.Ejectile.GSMass + self.Residual.GSMass - np.sqrt(self.Projectile.GSMass*self.Ejectile.GSMass*self.BKE/ejectKE)*np.cos(self.Theta)
		return -1.0*K*rho*self.DISP*self.MAG

	def ChangeReactionParameters(self, bke, theta, bfield) :
		self.BKE = bke
		self.Theta = theta*self.DEG2RAD
		self.Bfield = bfield