###############################################################################
# This file is part of SWIFT.
# Copyright (c) 2016 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
N = int(sys.argv[2])  # Write N particles at a time to avoid requiring a lot of RAM
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_%d.hdf5" % L

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

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

n_iterations = numPart / N
remainder = numPart % N

print(
    "Writing",
    numPart,
    "in",
    n_iterations,
    "iterations of size",
    N,
    "and a remainder of",
    remainder,
)

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

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

# Header
grp = file.create_group("/Header")
grp.attrs["BoxSize"] = boxSize
grp.attrs["NumPart_Total"] = [numPart % (int(1) << 32), 0, 0, 0, 0, 0]
grp.attrs["NumPart_Total_HighWord"] = [numPart / (int(1) << 32), 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

# Runtime parameters
grp = file.create_group("/RuntimePars")
grp.attrs["PeriodicBoundariesOn"] = periodic

# 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")

# First create the arrays in the file
ds_v = grp.create_dataset(
    "Velocities", (numPart, 3), "f", chunks=True, compression="gzip"
)
ds_m = grp.create_dataset("Masses", (numPart, 1), "f", chunks=True, compression="gzip")
ds_h = grp.create_dataset(
    "SmoothingLength", (numPart, 1), "f", chunks=True, compression="gzip"
)
ds_u = grp.create_dataset(
    "InternalEnergy", (numPart, 1), "f", chunks=True, compression="gzip"
)
ds_id = grp.create_dataset(
    "ParticleIDs", (numPart, 1), "L", chunks=True, compression="gzip"
)
ds_x = grp.create_dataset(
    "Coordinates", (numPart, 3), "d", chunks=True, compression="gzip"
)

# Now loop and create parts of the dataset
offset = 0
for n in range(n_iterations):
    v = zeros((N, 3))
    ds_v[offset : offset + N, :] = v
    v = zeros(1)

    m = full((N, 1), mass)
    ds_m[offset : offset + N] = m
    m = zeros(1)

    h = full((N, 1), eta * boxSize / L)
    ds_h[offset : offset + N] = h
    h = zeros(1)

    u = full((N, 1), internalEnergy)
    ds_u[offset : offset + N] = u
    u = zeros(1)

    ids = linspace(offset, offset + N, N, endpoint=False).reshape((N, 1))
    ds_id[offset : offset + N] = ids + 1
    x = ids % L
    y = ((ids - x) / L) % L
    z = (ids - x - L * y) / L ** 2
    ids = zeros(1)
    coords = zeros((N, 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_x[offset : offset + N, :] = coords
    coords = zeros((1, 3))

    offset += N
    print("Done", offset, "/", numPart, "(%.1f %%)" % (100 * (float)(offset) / numPart))

# And now, the remainder
v = zeros((remainder, 3))
ds_v[offset : offset + remainder, :] = v
v = zeros(1)

m = full((remainder, 1), mass)
ds_m[offset : offset + remainder] = m
m = zeros(1)

h = full((remainder, 1), eta * boxSize / L)
ds_h[offset : offset + remainder] = h
h = zeros(1)

u = full((remainder, 1), internalEnergy)
ds_u[offset : offset + remainder] = u
u = zeros(1)

ids = linspace(offset, offset + remainder, remainder, endpoint=False).reshape(
    (remainder, 1)
)
ds_id[offset : offset + remainder] = ids + 1
x = ids % L
y = ((ids - x) / L) % L
z = (ids - x - L * y) / L ** 2
coords = zeros((remainder, 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)
ods_x[offset : offset + remainder, :] = coords

print("Done", offset + remainder, "/", numPart)


file.close()