"""Utilities for preparing datasets and inference inputs for the binary coronary bundle."""

import logging
import multiprocessing
import os
import resource

from typing import Dict, List, Optional, Union

import monai  # type: ignore
import psutil
import torch  # type: ignore


logger = logging.getLogger(__name__)

USE_AMP = monai.utils.get_torch_version_tuple() >= (1, 6)  # type: ignore


def num_workers() -> int:
    """Return a conservative worker count based on CPU, RAM and file descriptor limits."""

    n_workers = max(multiprocessing.cpu_count() - 1, 1)

    available_ram_in_gb = psutil.virtual_memory()[0] / 1024**3
    max_workers = int(available_ram_in_gb // 4)
    if max_workers < n_workers:
        n_workers = max_workers

    soft_limit, hard_limit = resource.getrlimit(resource.RLIMIT_NOFILE)
    resource.setrlimit(resource.RLIMIT_CORE, (resource.RLIM_INFINITY, resource.RLIM_INFINITY))
    max_workers = soft_limit // 256

    if max_workers < n_workers:
        logger.info(
            "Open file handle limit (%s) constrains multiprocessing; switching to file_system sharing.",
            soft_limit,
        )
        n_workers = min(16, n_workers)
        torch.multiprocessing.set_sharing_strategy("file_system")

    # Cap at 16 workers max regardless of system resources
    n_workers = min(16, n_workers)
    logger.info("using number of workers: %s", n_workers)

    return n_workers


IMAGE_FILE_EXT = [".nii", ".nii.gz", ".nrrd", ".dcm"]


def parse_data_for_inference(fn_or_dir: Optional[str] = None) -> Union[None, List[Dict[str, str]]]:
    """Convert filepath to data_dict for inference runs."""

    if not fn_or_dir:
        return None

    if os.path.isfile(fn_or_dir):
        data_dict = [{"image": fn_or_dir}]
    elif os.path.isdir(fn_or_dir):
        files = sorted(
            [fn for fn in os.listdir(fn_or_dir) if any(fn.endswith(ext) for ext in IMAGE_FILE_EXT)]
        )
        data_dict = [{"image": os.path.join(fn_or_dir, fn)} for fn in files]
    else:
        raise FileNotFoundError(fn_or_dir)

    return data_dict