import os

os.environ["EQX_ON_ERROR"] = "nan"  # avoid an allgather caused by diffrax
import jax

jax.distributed.initialize()

rank = jax.process_index()
size = jax.process_count()

import jax.numpy as jnp
import jax_cosmo as jc
import numpy as np
from diffrax import Dopri5, ODETerm, PIDController, SaveAt, diffeqsolve
from jax.experimental import mesh_utils
from jax.sharding import Mesh, NamedSharding
from jax.sharding import PartitionSpec as P

from jaxpm.kernels import interpolate_power_spectrum
from jaxpm.painting import cic_paint_dx
from jaxpm.pm import linear_field, lpt, make_ode_fn

size = 256
mesh_shape = [size] * 3
box_size = [float(size)] * 3
snapshots = jnp.linspace(0.1, 1., 4)
halo_size = 64
if jax.device_count() > 1:

    pdims = (4, 2)
    devices = mesh_utils.create_device_mesh(pdims)
    mesh = Mesh(devices.T, axis_names=('x', 'y'))
    sharding = NamedSharding(mesh, P('x', 'y'))


@jax.jit
def run_simulation(omega_c, sigma8):
    # Create a small function to generate the matter power spectrum
    k = jnp.logspace(-4, 1, 128)
    pk = jc.power.linear_matter_power(
        jc.Planck15(Omega_c=omega_c, sigma8=sigma8), k)

    pk_fn = lambda x: interpolate_power_spectrum(x, k, pk)
    # Create initial conditions
    initial_conditions = linear_field(mesh_shape,
                                      box_size,
                                      pk_fn,
                                      seed=jax.random.PRNGKey(0))

    # Create particles
    particles = jnp.stack(jnp.meshgrid(*[jnp.arange(s) for s in mesh_shape]),
                          axis=-1).reshape([-1, 3])

    cosmo = jc.Planck15(Omega_c=omega_c, sigma8=sigma8)

    # Initial displacement
    dx, p, _ = lpt(cosmo, initial_conditions, 0.1, halo_size=halo_size)

    # Evolve the simulation forward
    ode_fn = make_ode_fn(mesh_shape, halo_size=halo_size)
    term = ODETerm(
        lambda t, state, args: jnp.stack(ode_fn(state, t, args), axis=0))
    solver = Dopri5()

    stepsize_controller = PIDController(rtol=1e-4, atol=1e-4)
    res = diffeqsolve(term,
                      solver,
                      t0=0.1,
                      t1=1.,
                      dt0=0.01,
                      y0=jnp.stack([dx, p], axis=0),
                      args=cosmo,
                      saveat=SaveAt(ts=snapshots),
                      stepsize_controller=stepsize_controller)

    # Return the simulation volume at requested
    states = res.ys
    field = cic_paint_dx(dx, halo_size=halo_size)
    final_fields = [
        cic_paint_dx(state[0], halo_size=halo_size) for state in states
    ]

    return initial_conditions, field, final_fields, res.stats


# Run the simulation
if jax.device_count() > 1:
    with mesh:
        init, field, final_fields, stats = run_simulation(0.32, 0.8)

else:
    init, field, final_fields, stats = run_simulation(0.32, 0.8)

# # Print the statistics
print(stats)

# # save the final state
np.save(f'initial_conditions_{rank}.npy', init.addressable_data(0))
np.save(f'field_{rank}.npy', field.addressable_data(0))

if final_fields is not None:
    for i, final_field in enumerate(final_fields):
        np.save(f'final_field_{i}_{rank}.npy', final_field.addressable_data(0))

print(f"Finished!!")