"""
Locking mechanism to ensure no two compilations occur simultaneously
in the same compilation directory (which can cause crashes).
"""
import os
import threading
from contextlib import contextmanager
from typing import Optional, Union

import filelock

from aesara.configdefaults import config


__all__ = [
    "force_unlock",
    "lock_ctx",
]


class ThreadFileLocks(threading.local):
    def __init__(self):
        self._locks = {}


local_mem = ThreadFileLocks()


def force_unlock(lock_dir: os.PathLike):
    """Forces the release of the lock on a specific directory.

    Parameters
    ----------
    lock_dir : os.PathLike
        Path to a directory that was locked with `lock_ctx`.
    """

    fl = filelock.FileLock(os.path.join(lock_dir, ".lock"))
    fl.release(force=True)

    dir_key = f"{lock_dir}-{os.getpid()}"

    if dir_key in local_mem._locks:
        del local_mem._locks[dir_key]


@contextmanager
def lock_ctx(
    lock_dir: Union[str, os.PathLike] = None, *, timeout: Optional[float] = None
):
    """Context manager that wraps around FileLock and SoftFileLock from filelock package.

    Parameters
    ----------
    lock_dir
        A directory for which to acquire the lock.
        Defaults to `aesara.config.compiledir`.
    timeout
        Timeout in seconds for waiting in lock acquisition.
        Defaults to `aesara.config.compile__timeout`.
    """
    if lock_dir is None:
        lock_dir = config.compiledir

    if timeout is None:
        timeout = config.compile__timeout

    # locks are kept in a dictionary to account for changing compiledirs
    dir_key = f"{lock_dir}-{os.getpid()}"

    if dir_key not in local_mem._locks:
        local_mem._locks[dir_key] = True
        fl = filelock.FileLock(os.path.join(lock_dir, ".lock"))
        fl.acquire(timeout=timeout)
        try:
            yield
        finally:
            if fl.is_locked:
                fl.release()
            if dir_key in local_mem._locks:
                del local_mem._locks[dir_key]
    else:
        yield
