import os
import re
import random
import time
import torch
import numpy as np
from os import path as osp

from .dist_util import master_only
from .logger import get_root_logger


# ---------------------------
#   GPU / MPS Compatibility
# ---------------------------

# Check if PyTorch ≥ 1.12 for MPS (Apple Silicon)
try:
    version_match = re.findall(
        r"^([0-9]+)\.([0-9]+)\.([0-9]+)",
        torch.__version__
    )[0]
    IS_HIGH_VERSION = [int(x) for x in version_match] >= [1, 12, 0]
except:
    IS_HIGH_VERSION = False


def gpu_is_available():
    """Return True if CUDA or MPS is available."""
    if IS_HIGH_VERSION and torch.backends.mps.is_available():
        return True
    return torch.cuda.is_available() and torch.backends.cudnn.is_available()


def get_device(gpu_id=None):
    """Return the best available device (MPS → CUDA → CPU)."""

    gpu_str = f":{gpu_id}" if isinstance(gpu_id, int) else ""

    # Apple MPS
    if IS_HIGH_VERSION and torch.backends.mps.is_available():
        return torch.device("mps")

    # NVIDIA CUDA
    if torch.cuda.is_available() and torch.backends.cudnn.is_available():
        return torch.device("cuda" + gpu_str)

    # CPU fallback
    return torch.device("cpu")


# ---------------------------
#   Utilities
# ---------------------------

def set_random_seed(seed):
    """Set random seeds."""
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)
    if torch.cuda.is_available():
        torch.cuda.manual_seed(seed)
        torch.cuda.manual_seed_all(seed)


def get_time_str():
    return time.strftime('%Y%m%d_%H%M%S', time.localtime())


def mkdir_and_rename(path):
    if osp.exists(path):
        new_name = path + '_archived_' + get_time_str()
        print(f'Path already exists. Renamed to {new_name}', flush=True)
        os.rename(path, new_name)
    os.makedirs(path, exist_ok=True)


@master_only
def make_exp_dirs(opt):
    path_opt = opt['path'].copy()
    if opt['is_train']:
        mkdir_and_rename(path_opt.pop('experiments_root'))
    else:
        mkdir_and_rename(path_opt.pop('results_root'))

    for key, path in path_opt.items():
        if ('strict_load' not in key) and ('pretrain_network' not in key) and ('resume' not in key):
            os.makedirs(path, exist_ok=True)


def scandir(dir_path, suffix=None, recursive=False, full_path=False):
    root = dir_path

    def _scan(path):
        for entry in os.scandir(path):
            if entry.is_file() and not entry.name.startswith('.'):
                file_path = entry.path if full_path else osp.relpath(entry.path, root)
                if suffix is None or file_path.endswith(suffix):
                    yield file_path
            elif entry.is_dir() and recursive:
                yield from _scan(entry.path)

    return _scan(dir_path)


def check_resume(opt, resume_iter):
    logger = get_root_logger()

    if opt['path']['resume_state']:
        networks = [k for k in opt.keys() if k.startswith('network_')]
        flag_pretrain = any(opt['path'].get(f'pretrain_{n}') for n in networks)

        if flag_pretrain:
            logger.warning('pretrain_network path will be ignored during resuming.')

        for network in networks:
            basename = network.replace('network_', '')
            if opt['path'].get('ignore_resume_networks') is None or (
                basename not in opt['path']['ignore_resume_networks']
            ):
                opt['path'][f'pretrain_{network}'] = osp.join(
                    opt['path']['models'], f'net_{basename}_{resume_iter}.pth'
                )
                logger.info(f"Set pretrain for {network}")


def sizeof_fmt(size, suffix='B'):
    for unit in ['', 'K', 'M', 'G', 'T', 'P']:
        if size < 1024:
            return f"{size:3.1f} {unit}{suffix}"
        size /= 1024
    return f"{size:3.1f} Y{suffix}"