import os
import subprocess
import sys
import sysconfig
import tempfile
from contextlib import nullcontext
from importlib import resources
from pathlib import Path
from shutil import copy2


__all__ = ["version", "bootstrap"]
_PIP_VERSION = "26.2.1"

# Directory of system wheel packages. Some Linux distribution packaging
# policies recommend against bundling dependencies. For example, Fedora
# installs wheel packages in the /usr/share/python-wheels/ directory and don't
# install the ensurepip._bundled package.
_pkg_dir = sysconfig.get_config_var('WHEEL_PKG_DIR')
if _pkg_dir:
    _WHEEL_PKG_DIR = Path(_pkg_dir).resolve()
else:
    _WHEEL_PKG_DIR = None


def _find_wheel_pkg_dir_pip():
    if _WHEEL_PKG_DIR is None:
        # NOTE: The compile-time `WHEEL_PKG_DIR` is unset so there is no place
        # NOTE: for looking up the wheels.
        return None

    dist_matching_wheels = _WHEEL_PKG_DIR.glob('pip-*.whl')
    try:
        last_matching_dist_wheel = sorted(dist_matching_wheels)[-1]
    except IndexError:
        # NOTE: `WHEEL_PKG_DIR` does not contain any wheel files for `pip`.
        return None

    return nullcontext(last_matching_dist_wheel)


def _get_pip_whl_path_ctx():
    # Prefer pip from the wheel package directory, if present.
    if (alternative_pip_wheel_path := _find_wheel_pkg_dir_pip()) is not None:
        return alternative_pip_wheel_path

    return resources.as_file(
        resources.files('ensurepip')
        / '_bundled'
        / f'pip-{_PIP_VERSION}-py3-none-any.whl'
    )


def _get_pip_version():
    with _get_pip_whl_path_ctx() as bundled_wheel_path:
        wheel_name = bundled_wheel_path.name
        return (
            # Extract '21.2.4' from 'pip-21.2.4-py3-none-any.whl'
            wheel_name.
            removeprefix('pip-').
            partition('-')[0]
        )


def _run_pip(args, additional_paths=None):
    # Run the bootstrapping in a subprocess to avoid leaking any state that happens
    # after pip has executed. Particularly, this avoids the case when pip holds onto
    # the files in *additional_paths*, preventing us to remove them at the end of the
    # invocation.
    code = f"""
import runpy
import sys
sys.path = {additional_paths or []} + sys.path
sys.argv[1:] = {args}
runpy.run_module("pip", run_name="__main__", alter_sys=True)
"""

    cmd = [
        sys.executable,
        '-W',
        'ignore::DeprecationWarning',
        '-c',
        code,
    ]
    if sys.flags.isolated:
        # run code in isolated mode if currently running isolated
        cmd.insert(1, '-I')
    return subprocess.run(cmd, check=True).returncode


def version():
    """
    Returns a string specifying the bundled version of pip.
    """
    return _get_pip_version()


def _disable_pip_configuration_settings():
    # We deliberately ignore all pip environment variables
    # when invoking pip
    # See http://bugs.python.org/issue19734 for details
    keys_to_remove = [k for k in os.environ if k.startswith("PIP_")]
    for k in keys_to_remove:
        del os.environ[k]
    # We also ignore the settings in the default pip configuration file
    # See http://bugs.python.org/issue20053 for details
    os.environ['PIP_CONFIG_FILE'] = os.devnull


def bootstrap(*, root=None, upgrade=False, user=False,
              altinstall=False, default_pip=False,
              verbosity=0):
    """
    Bootstrap pip into the current Python installation (or the given root
    directory).

    Note that calling this function will alter both sys.path and os.environ.
    """
    # Discard the return value
    _bootstrap(root=root, upgrade=upgrade, user=user,
               altinstall=altinstall, default_pip=default_pip,
               verbosity=verbosity)


def _bootstrap(*, root=None, upgrade=False, user=False,
              altinstall=False, default_pip=False,
              verbosity=0):
    """
    Bootstrap pip into the current Python installation (or the given root
    directory). Returns pip command status code.

    Note that calling this function will alter both sys.path and os.environ.
    """

    try:
        import zlib
    except ImportError:
        raise ModuleNotFoundError(
            "ensurepip requires the standard library module 'zlib' "
            "to install pip."
        ) from None

    if altinstall and default_pip:
        raise ValueError("Cannot use altinstall and default_pip together")

    sys.audit("ensurepip.bootstrap", root)

    _disable_pip_configuration_settings()

    # By default, installing pip installs all of the
    # following scripts (X.Y == running Python version):
    #
    #   pip, pipX, pipX.Y
    #
    # pip 1.5+ allows ensurepip to request that some of those be left out
    if altinstall:
        # omit pip, pipX
        os.environ["ENSUREPIP_OPTIONS"] = "altinstall"
    elif not default_pip:
        # omit pip
        os.environ["ENSUREPIP_OPTIONS"] = "install"

    with tempfile.TemporaryDirectory() as tmpdir:
        # Put our bundled wheels into a temporary directory and construct the
        # additional paths that need added to sys.path
        tmpdir_path = Path(tmpdir)
        with _get_pip_whl_path_ctx() as bundled_wheel_path:
            tmp_wheel_path = tmpdir_path / bundled_wheel_path.name
            copy2(bundled_wheel_path, tmp_wheel_path)

        # Construct the arguments to be passed to the pip command
        args = ["install", "--no-cache-dir", "--no-index", "--find-links", tmpdir]
        if root:
            args += ["--root", root]
        if upgrade:
            args += ["--upgrade"]
        if user:
            args += ["--user"]
        if verbosity:
            args += ["-" + "v" * verbosity]
        if sys.implementation.cache_tag is None:
            args += ["--no-compile"]

        return _run_pip([*args, "pip"], [os.fsdecode(tmp_wheel_path)])


def _uninstall_helper(*, verbosity=0):
    """Helper to support a clean default uninstall process on Windows

    Note that calling this function may alter os.environ.
    """
    # Nothing to do if pip was never installed, or has been removed
    try:
        import pip
    except ImportError:
        return

    # If the installed pip version doesn't match the available one,
    # leave it alone
    available_version = version()
    if pip.__version__ != available_version:
        print(f"ensurepip will only uninstall a matching version "
              f"({pip.__version__!r} installed, "
              f"{available_version!r} available)",
              file=sys.stderr)
        return

    _disable_pip_configuration_settings()

    # Construct the arguments to be passed to the pip command
    args = ["uninstall", "-y", "--disable-pip-version-check"]
    if verbosity:
        args += ["-" + "v" * verbosity]

    return _run_pip([*args, "pip"])


def _main(argv=None):
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--version",
        action="version",
        version="pip {}".format(version()),
        help="Show the version of pip that is bundled with this Python.",
    )
    parser.add_argument(
        "-v", "--verbose",
        action="count",
        default=0,
        dest="verbosity",
        help=("Give more output. Option is additive, and can be used up to 3 "
              "times."),
    )
    parser.add_argument(
        "-U", "--upgrade",
        action="store_true",
        default=False,
        help="Upgrade pip and dependencies, even if already installed.",
    )
    parser.add_argument(
        "--user",
        action="store_true",
        default=False,
        help="Install using the user scheme.",
    )
    parser.add_argument(
        "--root",
        default=None,
        help="Install everything relative to this alternate root directory.",
    )
    parser.add_argument(
        "--altinstall",
        action="store_true",
        default=False,
        help=("Make an alternate install, installing only the X.Y versioned "
              "scripts (Default: pipX, pipX.Y)."),
    )
    parser.add_argument(
        "--default-pip",
        action="store_true",
        default=False,
        help=("Make a default pip install, installing the unqualified pip "
              "in addition to the versioned scripts."),
    )

    args = parser.parse_args(argv)

    return _bootstrap(
        root=args.root,
        upgrade=args.upgrade,
        user=args.user,
        verbosity=args.verbosity,
        altinstall=args.altinstall,
        default_pip=args.default_pip,
    )
