################################################################################
# This file is part of SWIFT.
# Copyright (c) 2018 Bert Vandenbroucke (bert.vandenbroucke@gmail.com)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
################################################################################

# Computes the analytical solution of the Zeldovich pancake and compares with
# the simulation result

# Parameters
T_i = 100.0  # Initial temperature of the gas (in K)
z_c = 1.0  # Redshift of caustic formation (non-linear collapse)
z_i = 100.0  # Initial redshift

# Physical constants needed for internal energy to temperature conversion
k_in_J_K = 1.38064852e-23
mH_in_kg = 1.6737236e-27

import matplotlib

matplotlib.use("Agg")
import matplotlib.pyplot as plt
import numpy as np
import h5py
import sys
import os.path

plt.style.use("../../../tools/stylesheets/mnras.mplstyle")

snap = int(sys.argv[1])

# Read the simulation data
sim = h5py.File("zeldovichPancake_%04d.hdf5" % snap, "r")
boxSize = sim["/Header"].attrs["BoxSize"][0]
time = sim["/Header"].attrs["Time"][0]
redshift = sim["/Header"].attrs["Redshift"][0]
a = sim["/Header"].attrs["Scale-factor"][0]
scheme = sim["/HydroScheme"].attrs["Scheme"]
kernel = sim["/HydroScheme"].attrs["Kernel function"]
neighbours = sim["/HydroScheme"].attrs["Kernel target N_ngb"]
eta = sim["/HydroScheme"].attrs["Kernel eta"]
alpha = sim["/HydroScheme"].attrs["Alpha viscosity"]
git = sim["Code"].attrs["Git Revision"]

# Cosmological parameters
H_0 = sim["/Cosmology"].attrs["H0 [internal units]"][0]
gas_gamma = sim["/HydroScheme"].attrs["Adiabatic index"][0]

x = sim["/PartType0/Coordinates"][:, 0]
v = sim["/PartType0/Velocities"][:, 0]
u = sim["/PartType0/InternalEnergies"][:]
S = sim["/PartType0/Entropies"][:]
P = sim["/PartType0/Pressures"][:]
rho = sim["/PartType0/Densities"][:]
m = sim["/PartType0/Masses"][:]
try:
    phi = sim["/PartType0/Potentials"][:]
except KeyError:
    # We didn't write the potential, try to go on without
    print("Couldn't find potential in your output file")
    phi = np.zeros_like(m)

x -= 0.5 * boxSize

# Check for Gadget solution
filename_g = "snapshot_%03d.hdf5" % (snap)
if os.path.exists(filename_g):
    sim_g = h5py.File(filename_g, "r")
    x_g = sim_g["/PartType0/Coordinates"][:, 0]
    v_g = sim_g["/PartType0/Velocities"][:, 0]
    u_g = sim_g["/PartType0/InternalEnergies"][:]
    rho_g = sim_g["/PartType0/Densities"][:]
    phi_g = sim_g["/PartType0/Potential"][:]
    a_g = sim_g["/Header"].attrs["Time"]
    print("Gadget Scale-factor:", a_g, "redshift:", 1 / a_g - 1.0)

    x_g -= 0.5 * boxSize
else:
    x_g = np.zeros(1)
    v_g = np.zeros(1)
    u_g = np.zeros(1)
    rho_g = np.zeros(1)
    phi_g = np.zeros(1)

# Derived parameters
rho_0 = m.sum() / (boxSize ** 3)  # critical density of the box
lambda_i = boxSize  # wavelength of the perturbation


# Solution taken from Springel 2010. Eqs. 127 - 130
q = np.linspace(-0.5 * lambda_i, 0.5 * lambda_i, 256)
k_i = 2.0 * np.pi / lambda_i
zfac = (1.0 + z_c) / (1.0 + redshift)
x_s = q - zfac * np.sin(k_i * q) / k_i
rho_s = rho_0 / (1.0 - zfac * np.cos(k_i * q))
v_s = -H_0 * (1.0 + z_c) / np.sqrt(1.0 + redshift) * np.sin(k_i * q) / k_i
T_s = T_i * (((1.0 + redshift) / (1.0 + z_i)) ** 3.0 * rho_s / rho_0) ** (2.0 / 3.0)


unit_length_in_cgs = sim["/Units"].attrs["Unit length in cgs (U_L)"]
unit_mass_in_cgs = sim["/Units"].attrs["Unit mass in cgs (U_M)"]
unit_time_in_cgs = sim["/Units"].attrs["Unit time in cgs (U_t)"]

unit_length_in_si = 0.01 * unit_length_in_cgs
unit_mass_in_si = 0.001 * unit_mass_in_cgs
unit_time_in_si = unit_time_in_cgs

# Plot the interesting quantities
plt.figure(figsize=(7, 7 / 1.6))

line_color = "C4"
binned_color = "C2"
binned_marker_size = 4

scatter_props = dict(
    marker=".",
    ms=4,
    markeredgecolor="none",
    alpha=0.2,
    zorder=-1,
    rasterized=True,
    linestyle="none",
)

# Velocity profile --------------------------------
plt.subplot(231)
if np.size(x_g) > 1:
    plt.plot(x_g, v_g, "s", color="g", alpha=0.8, lw=1.2, ms=4)
plt.plot(x, v, **scatter_props)
plt.plot(x_s, v_s, "--", color=line_color, alpha=0.8, lw=1.2)
plt.xlabel("${\\rm{Comoving~position}}~x$", labelpad=0)
plt.ylabel("${\\rm{Peculiar~velocity}}~v_x$", labelpad=0)


# Density profile --------------------------------
plt.subplot(232)  # , yscale="log")
if np.size(x_g) > 1:
    plt.plot(x_g, rho_g / rho_0, "s", color="g", alpha=0.8, lw=1.2, ms=4)
plt.plot(x, rho / rho_0, **scatter_props)
plt.plot(x_s, rho_s / rho_0, "--", color=line_color, alpha=0.8, lw=1.2)
plt.xlabel("${\\rm{Comoving~position}}~x$", labelpad=0)
plt.ylabel("${\\rm{Density}}~\\rho / \\rho_0$", labelpad=0)

# Potential profile --------------------------------
plt.subplot(233)
if np.size(x_g) > 1:
    plt.plot(x_g, phi_g, "s", color="g", alpha=0.8, lw=1.2, ms=4)
plt.plot(x, phi, **scatter_props)
plt.xlabel("${\\rm{Comoving~position}}~x$", labelpad=0)
plt.ylabel("${\\rm{Potential}}~\\phi$", labelpad=0)

# Temperature profile -------------------------
plt.subplot(234)  # , yscale="log")
u *= unit_length_in_si ** 2 / unit_time_in_si ** 2
u_g *= unit_length_in_si ** 2 / unit_time_in_si ** 2
u /= a ** (3 * (gas_gamma - 1.0))
u_g /= a ** (3 * (gas_gamma - 1.0))
T = (gas_gamma - 1.0) * u * mH_in_kg / k_in_J_K
T_g = (gas_gamma - 1.0) * u_g * mH_in_kg / k_in_J_K
print("z = {0:.2f}, T_avg = {1:.2f}".format(redshift, T.mean()))
if np.size(x_g) > 1:
    plt.plot(x_g, T_g, "s", color="g", alpha=0.8, lw=1.2, ms=4)
plt.plot(x, T, **scatter_props)
plt.plot(x_s, T_s, "--", color=line_color, alpha=0.8, lw=1.2)
plt.xlabel("${\\rm{Comoving~position}}~x$", labelpad=0)
plt.ylabel("${\\rm{Temperature}}~T$", labelpad=0)

# Information -------------------------------------
plt.subplot(236, frameon=False)

text_fontsize = 5

plt.text(
    -0.45, 0.9, "Zeldovich pancake at z=%.2f " % (redshift), fontsize=text_fontsize
)
plt.text(
    -0.45,
    0.8,
    "adiabatic index $\\gamma=%.2f$, viscosity $\\alpha=%.2f$" % (gas_gamma, alpha),
    fontsize=text_fontsize,
)
plt.plot([-0.45, 0.1], [0.62, 0.62], "k-", lw=1)
plt.text(-0.45, 0.5, "$SWIFT$ %s" % git.decode("utf-8"), fontsize=text_fontsize)
plt.text(-0.45, 0.4, scheme.decode("utf-8"), fontsize=text_fontsize)
plt.text(-0.45, 0.3, kernel.decode("utf-8"), fontsize=text_fontsize)
plt.text(
    -0.45,
    0.2,
    "$%.2f$ neighbours ($\\eta=%.3f$)" % (neighbours, eta),
    fontsize=text_fontsize,
)
plt.xlim(-0.5, 0.5)
plt.ylim(0, 1)
plt.xticks([])
plt.yticks([])

plt.tight_layout()

plt.savefig("ZeldovichPancake_%.4d.png" % snap, dpi=200)