import glob
import os
import os.path
import pkgutil
import sys
import tempfile


__all__ = ["version", "bootstrap"]

def _ensurepip_is_disabled_in_debian_for_system():
    # Detect if ensurepip is being executed inside of a python-virtualenv
    # environment and return early if so.
    if hasattr(sys, 'real_prefix'):
        return

    # Detect if ensurepip is being executed inside of a stdlib venv
    # environment and return early if so.
    if sys.prefix != getattr(sys, "base_prefix", sys.prefix):
        return

    # If we've gotten here, then we are running inside of the system Python
    # and we don't want to use ensurepip to install into the system Python
    # so instead we'll redirect the user to using dpkg and apt-get.
    print('''\
ensurepip is disabled in Debian/Ubuntu for the system python.

Python modules for the system python are usually handled by dpkg and apt-get.

    apt-get install python-<module name>

Install the python-pip package to use pip itself.  Using pip together
with the system python might have unexpected results for any system installed
module, so use it on your own risk, or make sure to only use it in virtual
environments.
''')
    sys.exit(1)


# pip currently requires ssl support, so we try to provide a nicer
# error message when that is missing (http://bugs.python.org/issue19744)
_MISSING_SSL_MESSAGE = ("pip requires SSL/TLS")
try:
    import ssl
except ImportError:
    ssl = None
    def _require_ssl_for_pip():
        raise RuntimeError(_MISSING_SSL_MESSAGE)
else:
    def _require_ssl_for_pip():
        pass

_PROJECTS = [
    "setuptools",
    "pip",
    "pkg_resources",
]


def _run_pip(args, additional_paths=None):
    # Add our bundled software to the sys.path so we can import it
    if additional_paths is not None:
        sys.path = additional_paths + sys.path

    # Install the bundled software
    import pip
    pip.main(args)


def version():
    """
    Returns a string specifying the bundled version of pip.
    """
    wheel_names = glob.glob('/usr/share/python-wheels/pip-*.whl')
    assert len(wheel_names) == 1, wheel_names
    return os.path.basename(wheel_names[0]).split('-')[1]


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.
    """

    # Ensure that we are only running this inside of a virtual environment
    # of some kind.
    _ensurepip_is_disabled_in_debian_for_system()

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

    _require_ssl_for_pip()
    _disable_pip_configuration_settings()

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

    # Debian: The bundled wheels are useless to us because we must use ones
    # crafted from source code in the archive.  As we build the virtual
    # environment, copy the wheels from the system location into the virtual
    # environment, and place those wheels on sys.path.
    def copy_wheels(wheels, destdir, paths):
        for project in wheels:
            wheel_names = glob.glob(
                '/usr/share/python-wheels/{}-*.whl'.format(project))
            if len(wheel_names) == 0:
                raise RuntimeError('missing dependency wheel %s' % project)
            assert len(wheel_names) == 1, wheel_names
            wheel_name = os.path.basename(wheel_names[0])
            path = os.path.join('/usr/share/python-wheels', wheel_name)
            with open(path, 'rb') as fp:
                whl = fp.read()
            dest = os.path.join(destdir, wheel_name)
            with open(dest, 'wb') as fp:
                fp.write(whl)
            paths.append(dest)

    with tempfile.TemporaryDirectory() as tmpdir:
        # This directory is a "well known directory" which Debian has patched
        # pip to look in when attempting to locate wheels to use to satisfy
        # the dependencies that pip normally bundles but Debian has debundled.
        # This is critically important and if this directory changes then both
        # python-pip and python-virtualenv needs updated to match.
        venv_wheel_dir = os.path.join(sys.prefix, 'share', 'python-wheels')
        os.makedirs(venv_wheel_dir, exist_ok=True)
        dependencies = [
            os.path.basename(whl).split('-')[0]
            for whl in glob.glob('/usr/share/python-wheels/*.whl')
            ]
        copy_wheels(dependencies, venv_wheel_dir, sys.path)

        # Put our bundled wheels into a temporary directory and construct the
        # additional paths that need added to sys.path
        additional_paths = []
        copy_wheels(_PROJECTS, tmpdir, additional_paths)

        # Construct the arguments to be passed to the pip command
        args = ["install", "--no-index", "--find-links", tmpdir]
        if root:
            args += ["--root", root]
        if upgrade:
            args += ["--upgrade"]
        if user:
            args += ["--user"]
        if verbosity:
            args += ["-" + "v" * verbosity]

        _run_pip(args + _PROJECTS, additional_paths)

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 pip version doesn't match the bundled one, leave it alone
    # Disabled for Debian, always using the version from the python3-pip package.
    if False and pip.__version__ != _PIP_VERSION:
        msg = ("ensurepip will only uninstall a matching version "
               "({!r} installed, {!r} bundled)")
        print(msg.format(pip.__version__, _PIP_VERSION), file=sys.stderr)
        return

    _require_ssl_for_pip()
    _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]

    _run_pip(args + reversed(_PROJECTS))


def _main(argv=None):
    if ssl is None:
        print("Ignoring ensurepip failure: {}".format(_MISSING_SSL_MESSAGE),
              file=sys.stderr)
        return

    import argparse
    parser = argparse.ArgumentParser(prog="python -m ensurepip")
    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, easy_install-X.Y)"),
    )
    parser.add_argument(
        "--default-pip",
        action="store_true",
        default=False,
        help=("Make a default pip install, installing the unqualified pip "
              "and easy_install in addition to the versioned scripts"),
    )

    args = parser.parse_args(argv)

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