###############################################################################
# This file is part of SWIFT.
# Copyright (c) 2013 Pedro Gonnet (pedro.gonnet@durham.ac.uk),
#                    Matthieu Schaller (schaller@strw.leidenuniv.nl)
#
# 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/>.
#
##############################################################################

import h5py
import sys
from numpy import *

# Generates a swift IC file containing a cartesian distribution of particles
# at a constant density and pressure in a cubic box

# Parameters
periodic = 1  # 1 For periodic box
boxSize = 1.0
L = int(sys.argv[1])  # Number of particles along one axis
rho = 2.0  # Density
P = 1.0  # Pressure
gamma = 5.0 / 3.0  # Gas adiabatic index
eta = 1.2349  # 48 ngbs with cubic spline kernel
fileName = "uniformBox.hdf5"

# ---------------------------------------------------
numPart = L ** 3
mass = boxSize ** 3 * rho / numPart
internalEnergy = P / ((gamma - 1.0) * rho)

# --------------------------------------------------

# File
file = h5py.File(fileName, "w")

# Header
grp = file.create_group("/Header")
grp.attrs["BoxSize"] = boxSize
grp.attrs["NumPart_Total"] = [numPart, 0, 0, 0, 0, 0]
grp.attrs["NumPart_Total_HighWord"] = [0, 0, 0, 0, 0, 0]
grp.attrs["NumPart_ThisFile"] = [numPart, 0, 0, 0, 0, 0]
grp.attrs["Time"] = 0.0
grp.attrs["NumFilesPerSnapshot"] = 1
grp.attrs["MassTable"] = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
grp.attrs["Flag_Entropy_ICs"] = 0
grp.attrs["Dimension"] = 3

# Units
grp = file.create_group("/Units")
grp.attrs["Unit length in cgs (U_L)"] = 1.0
grp.attrs["Unit mass in cgs (U_M)"] = 1.0
grp.attrs["Unit time in cgs (U_t)"] = 1.0
grp.attrs["Unit current in cgs (U_I)"] = 1.0
grp.attrs["Unit temperature in cgs (U_T)"] = 1.0

# Particle group
grp = file.create_group("/PartType0")

v = zeros((numPart, 3))
ds = grp.create_dataset("Velocities", (numPart, 3), "f")
ds[()] = v
v = zeros(1)

m = full((numPart, 1), mass)
ds = grp.create_dataset("Masses", (numPart, 1), "f")
ds[()] = m
m = zeros(1)

h = full((numPart, 1), eta * boxSize / L)
ds = grp.create_dataset("SmoothingLength", (numPart, 1), "f")
ds[()] = h
h = zeros(1)

u = full((numPart, 1), internalEnergy)
ds = grp.create_dataset("InternalEnergy", (numPart, 1), "f")
ds[()] = u
u = zeros(1)


ids = linspace(0, numPart, numPart, endpoint=False).reshape((numPart, 1))
ds = grp.create_dataset("ParticleIDs", (numPart, 1), "L")
ds[()] = ids + 1
x = ids % L
y = ((ids - x) / L) % L
z = (ids - x - L * y) / L ** 2
coords = zeros((numPart, 3))
coords[:, 0] = z[:, 0] * boxSize / L + boxSize / (2 * L)
coords[:, 1] = y[:, 0] * boxSize / L + boxSize / (2 * L)
coords[:, 2] = x[:, 0] * boxSize / L + boxSize / (2 * L)
ds = grp.create_dataset("Coordinates", (numPart, 3), "d")
ds[()] = coords

file.close()