# Copyright (C) 2022 Richard Stiskalek
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU 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 General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
"""
MPI script to calculate the matter cross power spectrum between CSiBORG
IC realisations. Units are Mpc/h.
"""
from argparse import ArgumentParser
from datetime import datetime
from gc import collect
from itertools import combinations
from os import remove
from os.path import join

import joblib
import numpy
import Pk_library as PKL
from mpi4py import MPI

try:
    import csiborgtools
except ModuleNotFoundError:
    import sys
    sys.path.append("../")
    import csiborgtools


dumpdir = "/mnt/extraspace/rstiskalek/csiborg/"
parser = ArgumentParser()
parser.add_argument("--grid", type=int)
parser.add_argument("--halfwidth", type=float, default=0.5)
args = parser.parse_args()

# Get MPI things
comm = MPI.COMM_WORLD
rank = comm.Get_rank()
nproc = comm.Get_size()
MAS = "CIC"  # mass asignment scheme

paths = csiborgtools.read.Paths(**csiborgtools.paths_glamdring)
box = csiborgtools.read.CSiBORGBox(paths)
reader = csiborgtools.read.ParticleReader(paths)
ics = paths.get_ics()
nsims = len(ics)

# File paths
ftemp = join(dumpdir, "temp_crosspk",
             "out_{}_{}" + "_{}".format(args.halfwidth))
fout = join(dumpdir, "crosspk",
            "out_{}_{}" + "_{}.p".format(args.halfwidth))


jobs = csiborgtools.utils.split_jobs(nsims, nproc)[rank]
for n in jobs:
    print(f"Rank {rank} at {datetime.now()}: saving {n}th delta.", flush=True)
    nsim = ics[n]
    particles = reader.read_particle(max(paths.get_snapshots(nsim)), nsim,
                                     ["x", "y", "z", "M"], verbose=False)
    # Halfwidth -- particle selection
    if args.halfwidth < 0.5:
        particles = csiborgtools.read.halfwidth_select(
            args.halfwidth, particles)
        length = box.box2mpc(2 * args.halfwidth) * box.h  # Mpc/h
    else:
        length = box.box2mpc(1) * box.h  # Mpc/h
    # Calculate the overdensity field
    field = csiborgtools.field.DensityField(particles, length, box, MAS)
    delta = field.overdensity_field(args.grid, verbose=False)
    aexp = box._aexp

    # Try to clean up memory
    del field, particles, box, reader
    collect()

    # Dump the results
    with open(ftemp.format(nsim, "delta") + ".npy", "wb") as f:
        numpy.save(f, delta)
    joblib.dump([aexp, length], ftemp.format(nsim, "lengths") + ".p")

    # Try to clean up memory
    del delta
    collect()


comm.Barrier()

# Get off-diagonal elements and append the diagoal
combs = [c for c in combinations(range(nsims), 2)]
for i in range(nsims):
    combs.append((i, i))
prev_delta = [-1, None, None, None]  # i, delta, aexp, length

jobs = csiborgtools.utils.split_jobs(len(combs), nproc)[rank]
for n in jobs:
    i, j = combs[n]
    print("Rank {}@{}: combination {}.".format(rank, datetime.now(), (i, j)))

    # If i same as last time then don't have to load it
    if prev_delta[0] == i:
        delta_i = prev_delta[1]
        aexp_i = prev_delta[2]
        length_i = prev_delta[3]
    else:
        with open(ftemp.format(ics[i], "delta") + ".npy", "rb") as f:
            delta_i = numpy.load(f)
        aexp_i, length_i = joblib.load(ftemp.format(ics[i], "lengths") + ".p")
        # Store in prev_delta
        prev_delta[0] = i
        prev_delta[1] = delta_i
        prev_delta[2] = aexp_i
        prev_delta[3] = length_i

    # Get jth delta
    with open(ftemp.format(ics[j], "delta") + ".npy", "rb") as f:
        delta_j = numpy.load(f)
    aexp_j, length_j = joblib.load(ftemp.format(ics[j], "lengths") + ".p")

    # Verify the difference between the scale factors! Say more than 1%
    daexp = abs((aexp_i - aexp_j) / aexp_i)
    if daexp > 0.01:
        raise ValueError(
            "Boxes {} and {} final snapshot scale factors disagree by "
            "`{}` percent!".format(ics[i], ics[j], daexp * 100))
    # Check how well the boxsizes agree
    dlength = abs((length_i - length_j) / length_i)
    if dlength > 0.001:
        raise ValueError("Boxes {} and {} box sizes disagree by `{}` percent!"
                         .format(ics[i], ics[j], dlength * 100))

    # Calculate the cross power spectrum
    Pk = PKL.XPk([delta_i, delta_j], length_i, axis=1, MAS=[MAS, MAS],
                 threads=1)
    joblib.dump(Pk, fout.format(ics[i], ics[j]))

    del delta_i, delta_j, Pk
    collect()


# Clean up the temp files
comm.Barrier()
if rank == 0:
    print("Cleaning up the temporary files...")
    for ic in ics:
        remove(ftemp.format(ic, "delta") + ".npy")
        remove(ftemp.format(ic, "lengths") + ".p")

    print("All finished!")