#!/usr/bin/env python
"""
train.py
"""

from __future__ import annotations

import logging
import random
import socket
import traceback
from datetime import timedelta
from typing import Any, Callable, Optional

import dcargs
import numpy as np
import torch
import torch.distributed as dist
import torch.multiprocessing as mp
import yaml

from nerfstudio.configs import base as cfg
from nerfstudio.configs.base_configs import AnnotatedBaseConfigUnion
from nerfstudio.engine.trainer import train_loop
from nerfstudio.utils import comms, profiler

logging.basicConfig(format="[%(filename)s:%(lineno)d] %(message)s", level=logging.DEBUG)

DEFAULT_TIMEOUT = timedelta(minutes=30)

# speedup for when input size to model doesn't change (much)
torch.backends.cudnn.benchmark = True  # type: ignore


def _find_free_port() -> str:
    """Find free port on open socket"""
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.bind(("", 0))
    port = sock.getsockname()[1]
    sock.close()
    return port


def _set_random_seed(seed) -> None:
    """Set randomness seed in torch and numpy"""
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)


def _distributed_worker(
    local_rank: int,
    main_func: Callable,
    world_size: int,
    num_gpus_per_machine: int,
    machine_rank: int,
    dist_url: str,
    config: cfg.Config,
    timeout: timedelta = DEFAULT_TIMEOUT,
) -> Any:
    """Spawned distributed worker that handles the initialization of process group and handles the
       training process on multiple processes

    Args:
        local_rank (int): current rank of process
        main_func (Callable): function that will be called by the distributed workers
        world_size (int): total number of gpus available
        num_gpus_per_machine (int): number of GPUs per machine
        machine_rank (int): rank of this machine
        dist_url (str): url to connect to for distributed jobs, including protocol
                        e.g. "tcp://127.0.0.1:8686".
                        Can be set to "auto" to automatically select a free port on localhost
        config (Config): config file specifying training regimen
        timeout (timedelta, optional): timeout of the distributed workers Defaults to DEFAULT_TIMEOUT.

    Raises:
        e: Exception in initializing the process group

    Returns:
        Any: TODO(): determine the return type
    """
    assert torch.cuda.is_available(), "cuda is not available. Please check your installation."
    global_rank = machine_rank * num_gpus_per_machine + local_rank
    try:
        dist.init_process_group(
            backend="NCCL",
            init_method=dist_url,
            world_size=world_size,
            rank=global_rank,
            timeout=timeout,
        )
    except Exception as e:
        logging.error("Process group URL: %s", dist_url)
        raise e

    assert comms._LOCAL_PROCESS_GROUP is None  # pylint: disable=protected-access
    num_machines = world_size // num_gpus_per_machine
    for i in range(num_machines):
        ranks_on_i = list(range(i * num_gpus_per_machine, (i + 1) * num_gpus_per_machine))
        pg = dist.new_group(ranks_on_i)
        if i == machine_rank:
            comms._LOCAL_PROCESS_GROUP = pg  # pylint: disable=protected-access

    assert num_gpus_per_machine <= torch.cuda.device_count()
    torch.cuda.set_device(local_rank)
    _set_random_seed(config.machine.seed + global_rank)
    comms.synchronize(world_size)

    output = main_func(local_rank, world_size, config)
    comms.synchronize(world_size)
    dist.destroy_process_group()
    return output


def launch(
    main_func: Callable,
    num_gpus_per_machine: int,
    num_machines: int = 1,
    machine_rank: int = 0,
    dist_url: str = "auto",
    config: Optional[cfg.Config] = None,
    timeout: timedelta = DEFAULT_TIMEOUT,
) -> None:
    """Function that spawns muliple processes to call on main_func

    Args:
        main_func (Callable): function that will be called by the distributed workers
        num_gpus_per_machine (int): number of GPUs per machine
        num_machines (int, optional): total number of machines
        machine_rank (int, optional): rank of this machine.
        dist_url (str, optional): url to connect to for distributed jobs.
        config (Config, optional): config file specifying training regimen.
        timeout (timedelta, optional): timeout of the distributed workers.
    """
    assert config is not None
    world_size = num_machines * num_gpus_per_machine
    if world_size == 0:
        # Using only CPU and one process.
        _set_random_seed(config.machine.seed)
        main_func(local_rank=0, world_size=0, config=config)
    elif world_size == 1:
        # Using one gpu and one process.
        _set_random_seed(config.machine.seed)
        try:
            main_func(local_rank=0, world_size=1, config=config)
        except KeyboardInterrupt:
            print(traceback.format_exc())
        finally:
            profiler.flush_profiler(config.logging)
    elif world_size > 1:
        # Using multiple gpus with multiple processes.
        if dist_url == "auto":
            assert num_machines == 1, "dist_url=auto not supported in multi-machine jobs."
            port = _find_free_port()
            dist_url = f"tcp://127.0.0.1:{port}"
        if num_machines > 1 and dist_url.startswith("file://"):
            logging.warning("file:// is not a reliable init_method in multi-machine jobs. Prefer tcp://")

        process_context = mp.spawn(
            _distributed_worker,
            nprocs=num_gpus_per_machine,
            args=(
                main_func,
                world_size,
                num_gpus_per_machine,
                machine_rank,
                dist_url,
                config,
                timeout,
            ),
        )
        assert process_context is not None
        try:
            process_context.join()
        except KeyboardInterrupt:
            for i, process in enumerate(process_context.processes):
                if process.is_alive():
                    logging.info("Terminating process %s", str(i))
                    process.terminate()
                process.join()
                logging.info("Process %s finished", str(i))
        finally:
            profiler.flush_profiler(config.logging)


def main(config: cfg.Config) -> None:
    """Main function."""

    config.set_timestamp()

    if config.trainer.load_config:
        logging.info(f"Loading pre-set config from: {config.trainer.load_config}")
        config = yaml.load(config.trainer.load_config.read_text(), Loader=yaml.Loader)

    # print and save config
    config.print_to_terminal()
    config.save_config()

    launch(
        train_loop,
        config.machine.num_gpus,
        num_machines=config.machine.num_machines,
        machine_rank=config.machine.machine_rank,
        dist_url=config.machine.dist_url,
        config=config,
    )


def entrypoint():
    """Entrypoint for use with pyproject scripts."""
    # Choose a base configuration and override values.
    dcargs.extras.set_accent_color("bright_yellow")
    main(dcargs.cli(AnnotatedBaseConfigUnion))


if __name__ == "__main__":
    entrypoint()