import unittest
import numpy as np

from chroma.geometry import Solid, Geometry
from chroma.make import box
from chroma.sim import Simulation
from chroma.optics import water_wcsim
from chroma.event import Photons
import histogram
from histogram.root import rootify
import ROOT
ROOT.gROOT.SetBatch(1)

class TestRayleigh(unittest.TestCase):
    def setUp(self):
        self.cube = Geometry()
        self.cube.add_solid(Solid(box(100,100,100), water_wcsim, water_wcsim))
        self.cube.pmtids = [0]
        self.sim = Simulation(self.cube, water_wcsim, bvh_bits=4, geant4_processes=0,
                              use_cache=False)
        nphotons = 100000
        positions = np.tile([0,0,0], (nphotons,1)).astype(np.float32)
        directions = np.tile([0,0,1], (nphotons,1)).astype(np.float32)
        polarizations = np.zeros_like(positions)
        phi = np.random.uniform(0, 2*np.pi, nphotons).astype(np.float32)
        polarizations[:,0] = np.cos(phi)
        polarizations[:,1] = np.sin(phi)
        times = np.zeros(nphotons, dtype=np.float32)
        wavelengths = np.empty(nphotons, np.float32)
        wavelengths.fill(400.0)

        self.photons = Photons(positions=positions, directions=directions, polarizations=polarizations,
                               times=times, wavelengths=wavelengths)

    def testAngularDistributionPolarized(self):
        # Fully polarized photons
        self.photons.polarizations[:] = [1.0, 0.0, 0.0]

        photon_stop = self.sim.propagate_photons(self.photons, max_steps=1)
        aborted = (photon_stop.histories & (1 << 31)) > 0
        self.assertFalse(aborted.any())

        # Compute the dot product between initial and final directions
        rayleigh_scatters = (photon_stop.histories & (1 << 4)) > 0
        cos_scatter = (self.photons.directions[rayleigh_scatters] * photon_stop.directions[rayleigh_scatters]).sum(axis=1)
        theta_scatter = np.arccos(cos_scatter)
        h = histogram.Histogram(bins=100, range=(0, np.pi))
        h.fill(theta_scatter)
        h = rootify(h)

        # The functional form for polarized light should be (1 + \cos^2 \theta)\sin \theta
        # according to GEANT4 physics reference manual
        f = ROOT.TF1("pol_func", "[0]*(1+cos(x)**2)*sin(x)", 0, np.pi)
        h.Fit(f)
        self.assertGreater(f.GetProb(), 1e-3)