from __future__ import annotations

import atexit
import builtins
import io
import operator
import os
import threading

from ._config import DlpConfig
from ._errors import DlpConfigurationError
from ._session import DlpSession

_ORIGINAL_OPEN = builtins.open
_DEFAULT_BUFFER_SIZE = 1024 * 1024
_state_lock = threading.RLock()
_config = DlpConfig()
_default_session = None


def _validate_path_mode(mode, buffering, encoding, errors, newline) -> int:
    buffering = operator.index(buffering)
    if buffering < -1:
        raise ValueError("invalid buffering size")
    if not isinstance(mode, str):
        raise TypeError("open() argument 'mode' must be str, not %s" % type(mode).__name__)
    allowed = set("axrwb+t")
    invalid = set(mode) - allowed
    duplicate = any(mode.count(character) > 1 for character in allowed)
    if not mode or invalid or duplicate or sum(c in mode for c in "axrw") != 1:
        raise ValueError("invalid mode: %r" % mode)
    if "b" in mode and "t" in mode:
        raise ValueError("can't have text and binary mode at once")
    if "b" in mode:
        if encoding is not None:
            raise ValueError("binary mode doesn't take an encoding argument")
        if errors is not None:
            raise ValueError("binary mode doesn't take an errors argument")
        if newline is not None:
            raise ValueError("binary mode doesn't take a newline argument")
    elif buffering == 0:
        raise ValueError("can't have unbuffered text I/O")
    return buffering


def configure(*, python_executable=None, startup_timeout=60) -> None:
    """Configure the lazy default session before its first bridged read."""
    global _config
    with _state_lock:
        if _default_session is not None:
            raise DlpConfigurationError(
                "cannot configure dlp_io while the default session is active"
            )
        if startup_timeout <= 0:
            raise DlpConfigurationError("startup_timeout must be positive")
        _config = DlpConfig(
            python_executable=python_executable,
            startup_timeout=startup_timeout,
        )


def _get_default_session():
    global _default_session
    with _state_lock:
        if _default_session is None:
            _default_session = DlpSession.start(
                python_cmd=_config.python_command(),
                timeout=_config.startup_timeout,
            )
        return _default_session


def _wrap_reader(raw, mode, buffering, encoding, errors, newline):
    binary = "b" in mode
    if binary and buffering == 0:
        return raw
    if not binary and buffering == 0:
        raw.close()
        raise ValueError("can't have unbuffered text I/O")
    buffer_size = _DEFAULT_BUFFER_SIZE if buffering in (-1, 1) else buffering
    if buffer_size <= 0:
        raw.close()
        raise ValueError("invalid buffering size")
    buffered = io.BufferedReader(raw, buffer_size=buffer_size)
    if binary:
        return buffered
    return io.TextIOWrapper(
        buffered,
        encoding=encoding,
        errors=errors,
        newline=newline,
        line_buffering=buffering == 1,
    )


def open(
    file,
    mode="r",
    buffering=-1,
    encoding=None,
    errors=None,
    newline=None,
    closefd=True,
    opener=None,
):
    """Open a file with io.open-compatible calling conventions."""
    is_path = isinstance(file, (str, bytes, os.PathLike))
    if not is_path or opener is not None:
        return _ORIGINAL_OPEN(
            file,
            mode,
            buffering,
            encoding,
            errors,
            newline,
            closefd,
            opener,
        )
    buffering = _validate_path_mode(mode, buffering, encoding, errors, newline)
    if "+" in mode:
        raise io.UnsupportedOperation(
            "dlp_io does not support update mode for path-based files"
        )
    pure_read = "r" in mode
    if pure_read:
        if not closefd:
            raise ValueError("Cannot use closefd=False with file name")
        path = os.fsdecode(os.fspath(file))
        raw = _get_default_session().open_raw(path)
        return _wrap_reader(raw, mode, buffering, encoding, errors, newline)
    return _ORIGINAL_OPEN(file, mode, buffering, encoding, errors, newline, closefd)


def shutdown() -> None:
    """Close and forget the lazy default session. This operation is idempotent."""
    global _default_session
    with _state_lock:
        session = _default_session
        _default_session = None
    if session is not None:
        session.close()


atexit.register(shutdown)