"""External dependencies loader."""

import contextlib
import importlib
from pathlib import Path
import sys
import logging
import sysconfig
from types import ModuleType
from typing import Iterator, Iterable
import zipfile


_my_dir = Path(__file__).parent
_log = logging.getLogger(__name__)
_env_folder = Path(__file__).parent.joinpath("venv")

def load_wheel(module_name: str, submodules: Iterable[str]) -> list[ModuleType]:
    """Loads modules from a wheel file 'module_name*.whl'.

    Loads `module_name`, and if submodules are given, loads
    `module_name.submodule` for each of the submodules. This allows loading all
    required modules from the same wheel in one session, ensuring that
    inter-submodule references are correct.

    Returns the loaded modules, so [module, submodule, submodule, ...].
    """

    fname_prefix = _fname_prefix_from_module_name(module_name)
    wheel = _wheel_filename(fname_prefix)

    loaded_modules: list[ModuleType] = []
    to_load = [module_name] + [f"{module_name}.{submodule}" for submodule in submodules]

    # Load the module from the wheel file. Keep a backup of sys.path so that it
    # can be restored later. This should ensure that future import statements
    # cannot find this wheel file, increasing the separation of dependencies of
    # this add-on from other add-ons.
    with _sys_path_mod_backup(wheel):
        for modname in to_load:
            try:
                module = importlib.import_module(modname)
            except ImportError as ex:
                raise ImportError(
                    "Unable to load %r from %s: %s" % (modname, wheel, ex)
                ) from None
            assert isinstance(module, ModuleType)
            loaded_modules.append(module)
            _log.info("Loaded %s from %s", modname, module.__file__)

    assert len(loaded_modules) == len(
        to_load
    ), f"expecting to load {len(to_load)} modules, but only have {len(loaded_modules)}: {loaded_modules}"
    return loaded_modules


def load_wheel_global(module_name: str, fname_prefix: str = "", match_platform: bool = False) -> ModuleType:
    """Loads a wheel from 'fname_prefix*.whl', unless the named module can be imported.

    This allows us to use system-installed packages before falling back to the shipped wheels.
    This is useful for development, less so for deployment.

    If `fname_prefix` is the empty string, it will use the first package from `module_name`.
    In other words, `module_name="pkg.subpkg"` will result in `fname_prefix="pkg"`.
    """

    if not fname_prefix:
        fname_prefix = _fname_prefix_from_module_name(module_name)

    try:
        module = importlib.import_module(module_name)
    except ImportError as ex:
        _log.debug("Unable to import %s directly, will try wheel: %s", module_name, ex)
    else:
        _log.debug(
            "Was able to load %s from %s, no need to load wheel %s",
            module_name,
            module.__file__,
            fname_prefix,
        )
        return module

    wheel = _wheel_filename(fname_prefix, match_platform=match_platform)

    wheel_filepath = str(wheel)


    wheel_archive = zipfile.ZipFile(wheel_filepath)

    
    wheel_archive.extractall(_env_folder)

    if str(_env_folder) not in sys.path:
        sys.path.insert(0, str(_env_folder))

    try:
        module = importlib.import_module(module_name)
    except ImportError as ex:
        raise ImportError(
            "Unable to load %r from %s: %s" % (module_name, wheel, ex)
        ) from None

    _log.debug("Globally loaded %s from %s", module_name, module.__file__)
    return module


@contextlib.contextmanager
def _sys_path_mod_backup(wheel_file: Path) -> Iterator[None]:
    """Temporarily inserts a wheel onto sys.path.

    When the context exits, it restores sys.path and sys.modules, so that
    anything that was imported within the context remains unimportable by other
    modules.
    """
    old_syspath = sys.path[:]
    old_sysmod = sys.modules.copy()

    try:
        sys.path.insert(0, str(wheel_file))
        yield
    finally:
        # Restore without assigning a new list instance. That way references
        # held by other code will stay valid.
        sys.path[:] = old_syspath
        sys.modules.clear()
        sys.modules.update(old_sysmod)


def _wheel_filename(fname_prefix: str, match_platform: bool = False) -> Path:
    if match_platform:
        platform_tag = sysconfig.get_platform().replace('-','_').replace('.','_')
        path_pattern = f"{fname_prefix}*{platform_tag}.whl"
    else:
        path_pattern = f"{fname_prefix}*.whl"
    wheels: list[Path] = list(_my_dir.glob(path_pattern))
    if not wheels:
        raise RuntimeError("Unable to find wheel at %r" % path_pattern)

    # If there are multiple wheels that match, load the last-modified one.
    # Alphabetical sorting isn't going to cut it since BAT 1.10 was released.
    def modtime(filepath: Path) -> float:
        return filepath.stat().st_mtime

    wheels.sort(key=modtime)
    return wheels[-1]


def _fname_prefix_from_module_name(module_name: str) -> str:
    return module_name.split(".", 1)[0]