#!/usr/bin/env python

"""
Setuptools bootstrapping installer.

Run this script to install or upgrade setuptools.
"""

import os
import shutil
import sys
import tempfile
import zipfile
import optparse
import subprocess
import platform
import textwrap
import contextlib
import warnings

from distutils import log

try:
    from urllib.request import urlopen
except ImportError:
    from urllib2 import urlopen

try:
    from site import USER_SITE
except ImportError:
    USER_SITE = None

DEFAULT_VERSION = "21.2.1"
DEFAULT_URL = "https://pypi.python.org/packages/source/s/setuptools/"
DEFAULT_SAVE_DIR = os.curdir


def _python_cmd(*args):
    """
    Execute a command.

    Return True if the command succeeded.
    """
    args = (sys.executable,) + args
    return subprocess.call(args) == 0


def _install(archive_filename, install_args=()):
    """Install Setuptools."""
    with archive_context(archive_filename):
        # installing
        log.warn('Installing Setuptools')
        if not _python_cmd('setup.py', 'install', *install_args):
            log.warn('Something went wrong during the installation.')
            log.warn('See the error message above.')
            # exitcode will be 2
            return 2


def _build_egg(egg, archive_filename, to_dir):
    """Build Setuptools egg."""
    with archive_context(archive_filename):
        # building an egg
        log.warn('Building a Setuptools egg in %s', to_dir)
        _python_cmd('setup.py', '-q', 'bdist_egg', '--dist-dir', to_dir)
    # returning the result
    log.warn(egg)
    if not os.path.exists(egg):
        raise IOError('Could not build the egg.')


class ContextualZipFile(zipfile.ZipFile):

    """Supplement ZipFile class to support context manager for Python 2.6."""

    def __enter__(self):
        return self

    def __exit__(self, type, value, traceback):
        self.close()

    def __new__(cls, *args, **kwargs):
        """Construct a ZipFile or ContextualZipFile as appropriate."""
        if hasattr(zipfile.ZipFile, '__exit__'):
            return zipfile.ZipFile(*args, **kwargs)
        return super(ContextualZipFile, cls).__new__(cls)


@contextlib.contextmanager
def archive_context(filename):
    """
    Unzip filename to a temporary directory, set to the cwd.

    The unzipped target is cleaned up after.
    """
    tmpdir = tempfile.mkdtemp()
    log.warn('Extracting in %s', tmpdir)
    old_wd = os.getcwd()
    try:
        os.chdir(tmpdir)
        with ContextualZipFile(filename) as archive:
            archive.extractall()

        # going in the directory
        subdir = os.path.join(tmpdir, os.listdir(tmpdir)[0])
        os.chdir(subdir)
        log.warn('Now working in %s', subdir)
        yield

    finally:
        os.chdir(old_wd)
        shutil.rmtree(tmpdir)


def _do_download(version, download_base, to_dir, download_delay):
    """Download Setuptools."""
    egg = os.path.join(to_dir, 'setuptools-%s-py%d.%d.egg'
                       % (version, sys.version_info[0], sys.version_info[1]))
    if not os.path.exists(egg):
        archive = download_setuptools(version, download_base,
                                      to_dir, download_delay)
        _build_egg(egg, archive, to_dir)
    sys.path.insert(0, egg)

    # Remove previously-imported pkg_resources if present (see
    # https://bitbucket.org/pypa/setuptools/pull-request/7/ for details).
    if 'pkg_resources' in sys.modules:
        del sys.modules['pkg_resources']

    import setuptools
    setuptools.bootstrap_install_from = egg


def use_setuptools(
        version=DEFAULT_VERSION, download_base=DEFAULT_URL,
        to_dir=DEFAULT_SAVE_DIR, download_delay=15):
    """
    Ensure that a setuptools version is installed.

    Return None. Raise SystemExit if the requested version
    or later cannot be installed.
    """
    to_dir = os.path.abspath(to_dir)

    # prior to importing, capture the module state for
    # representative modules.
    rep_modules = 'pkg_resources', 'setuptools'
    imported = set(sys.modules).intersection(rep_modules)

    try:
        import pkg_resources
        pkg_resources.require("setuptools>=" + version)
        # a suitable version is already installed
        return
    except ImportError:
        # pkg_resources not available; setuptools is not installed; download
        pass
    except pkg_resources.DistributionNotFound:
        # no version of setuptools was found; allow download
        pass
    except pkg_resources.VersionConflict as VC_err:
        if imported:
            _conflict_bail(VC_err, version)

        # otherwise, unload pkg_resources to allow the downloaded version to
        #  take precedence.
        del pkg_resources
        _unload_pkg_resources()

    return _do_download(version, download_base, to_dir, download_delay)


def _conflict_bail(VC_err, version):
    """
    Setuptools was imported prior to invocation, so it is
    unsafe to unload it. Bail out.
    """
    conflict_tmpl = textwrap.dedent("""
        The required version of setuptools (>={version}) is not available,
        and can't be installed while this script is running. Please
        install a more recent version first, using
        'easy_install -U setuptools'.

        (Currently using {VC_err.args[0]!r})
        """)
    msg = conflict_tmpl.format(**locals())
    sys.stderr.write(msg)
    sys.exit(2)


def _unload_pkg_resources():
    del_modules = [
        name for name in sys.modules
        if name.startswith('pkg_resources')
    ]
    for mod_name in del_modules:
        del sys.modules[mod_name]


def _clean_check(cmd, target):
    """
    Run the command to download target.

    If the command fails, clean up before re-raising the error.
    """
    try:
        subprocess.check_call(cmd)
    except subprocess.CalledProcessError:
        if os.access(target, os.F_OK):
            os.unlink(target)