"""

We acquire the python information by running an interrogation script via subprocess trigger. This operation is not
cheap, especially not on Windows. To not have to pay this hefty cost every time we apply multiple levels of
caching.
"""  # noqa: D205

from __future__ import annotations

import hashlib
import importlib.util
import logging
import os
import random
import subprocess
import sys
from collections import OrderedDict
from pathlib import Path
from shlex import quote
from string import ascii_lowercase, ascii_uppercase, digits
from typing import TYPE_CHECKING

from virtualenv.app_data.na import AppDataDisabled
from virtualenv.cache import FileCache

if TYPE_CHECKING:
    from virtualenv.app_data.base import AppData
    from virtualenv.cache import Cache
from virtualenv.discovery.py_info import PythonInfo

_CACHE = OrderedDict()
_CACHE[Path(sys.executable)] = PythonInfo()
LOGGER = logging.getLogger(__name__)


def from_exe(  # noqa: PLR0913
    cls,
    app_data,
    exe,
    env=None,
    *,
    raise_on_error=True,
    ignore_cache=False,
    cache: Cache | None = None,
) -> PythonInfo | None:
    env = os.environ if env is None else env
    if cache is None:
        if app_data is None:
            app_data = AppDataDisabled()
        cache = FileCache(store_factory=app_data.py_info, clearer=app_data.py_info_clear)
    result = _get_from_cache(cls, app_data, exe, env, cache, ignore_cache=ignore_cache)
    if isinstance(result, Exception):
        if raise_on_error:
            raise result
        LOGGER.info("%s", result)
        result = None
    return result


def _get_from_cache(cls, app_data: AppData, exe: str, env, cache: Cache, *, ignore_cache: bool) -> PythonInfo:  # noqa: PLR0913
    # note here we cannot resolve symlinks, as the symlink may trigger different prefix information if there's a
    # pyenv.cfg somewhere alongside on python3.5+
    exe_path = Path(exe)
    if not ignore_cache and exe_path in _CACHE:  # check in the in-memory cache
        result = _CACHE[exe_path]
    else:  # otherwise go through the app data cache
        result = _CACHE[exe_path] = _get_via_file_cache(cls, app_data, exe_path, exe, env, cache)
    # independent if it was from the file or in-memory cache fix the original executable location
    if isinstance(result, PythonInfo):
        result.executable = exe
    return result


def _get_via_file_cache(cls, app_data: AppData, path: Path, exe: str, env, cache: Cache) -> PythonInfo:  # noqa: PLR0913
    # 1. get the hash of the probing script
    spec = importlib.util.find_spec("virtualenv.discovery.py_info")
    script = Path(spec.origin)
    try:
        py_info_hash = hashlib.sha256(script.read_bytes()).hexdigest()
    except OSError:
        py_info_hash = None

    # 2. get the mtime of the python executable
    try:
        path_modified = path.stat().st_mtime
    except OSError:
        path_modified = -1

    # 3. check if we have a valid cache entry
    py_info = None
    data = cache.get(path)
    if data is not None:
        if data.get("path") == str(path) and data.get("st_mtime") == path_modified and data.get("hash") == py_info_hash:
            py_info = cls._from_dict(data.get("content"))
            sys_exe = py_info.system_executable
            if sys_exe is not None and not os.path.exists(sys_exe):
                py_info = None  # if system executable is no longer there, this is not valid
        if py_info is None:
            cache.remove(path)  # if cache is invalid, remove it

    if py_info is None:  # if not loaded run and save
        failure, py_info = _run_subprocess(cls, exe, app_data, env)
        if failure is None:
            data = {
                "st_mtime": path_modified,
                "path": str(path),
                "content": py_info._to_dict(),  # noqa: SLF001
                "hash": py_info_hash,
            }
            cache.set(path, data)
        else:
            py_info = failure
    return py_info


COOKIE_LENGTH: int = 32


def gen_cookie():
    return "".join(
        random.choice(f"{ascii_lowercase}{ascii_uppercase}{digits}")  # noqa: S311
        for _ in range(COOKIE_LENGTH)
    )


def _run_subprocess(cls, exe, app_data, env):
    py_info_script = Path(os.path.abspath(__file__)).parent / "py_info.py"
    # Cookies allow to split the serialized stdout output generated by the script collecting the info from the output
    # generated by something else. The right way to deal with it is to create an anonymous pipe and pass its descriptor
    # to the child and output to it. But AFAIK all of them are either not cross-platform or too big to implement and are
    # not in the stdlib. So the easiest and the shortest way I could mind is just using the cookies.
    # We generate pseudorandom cookies because it easy to implement and avoids breakage from outputting modules source
    # code, i.e. by debug output libraries. We reverse the cookies to avoid breakages resulting from variable values
    # appearing in debug output.

    start_cookie = gen_cookie()
    end_cookie = gen_cookie()
    if app_data is None:
        app_data = AppDataDisabled()
    with app_data.ensure_extracted(py_info_script) as py_info_script:
        cmd = [exe, str(py_info_script), start_cookie, end_cookie]
        # prevent sys.prefix from leaking into the child process - see https://bugs.python.org/issue22490
        env = env.copy()
        env.pop("__PYVENV_LAUNCHER__", None)
        LOGGER.debug("get interpreter info via cmd: %s", LogCmd(cmd))
        try:
            process = subprocess.Popen(
                cmd,
                universal_newlines=True,
                stdin=subprocess.PIPE,
                stderr=subprocess.PIPE,
                stdout=subprocess.PIPE,
                env=env,
                encoding="utf-8",
            )
            out, err = process.communicate()
            code = process.returncode
        except OSError as os_error:
            out, err, code = "", os_error.strerror, os_error.errno
    result, failure = None, None
    if code == 0:
        out_starts = out.find(start_cookie[::-1])

        if out_starts > -1:
            pre_cookie = out[:out_starts]

            if pre_cookie:
                sys.stdout.write(pre_cookie)

            out = out[out_starts + COOKIE_LENGTH :]

        out_ends = out.find(end_cookie[::-1])

        if out_ends > -1:
            post_cookie = out[out_ends + COOKIE_LENGTH :]

            if post_cookie:
                sys.stdout.write(post_cookie)

            out = out[:out_ends]

        result = cls._from_json(out)
        result.executable = exe  # keep original executable as this may contain initialization code
    else:
        msg = f"{exe} with code {code}{f' out: {out!r}' if out else ''}{f' err: {err!r}' if err else ''}"
        failure = RuntimeError(f"failed to query {msg}")
    return failure, result


class LogCmd:
    def __init__(self, cmd, env=None) -> None:
        self.cmd = cmd
        self.env = env

    def __repr__(self) -> str:
        cmd_repr = " ".join(quote(str(c)) for c in self.cmd)
        if self.env is not None:
            cmd_repr = f"{cmd_repr} env of {self.env!r}"
        return cmd_repr


def clear(app_data=None, cache=None):
    """Clear the cache."""
    if cache is None and app_data is not None:
        cache = FileCache(store_factory=app_data.py_info, clearer=app_data.py_info_clear)
    if cache is not None:
        cache.clear()
    _CACHE.clear()


___all___ = [
    "from_exe",
    "clear",
    "LogCmd",
]