#!/usr/bin/env python
"""Aids in creating a developer virtual environment for Certbot.

When this module is run as a script, it takes the arguments that should
be passed to pip to install the Certbot packages as command line
arguments. The virtual environment will be created with the name "venv"
in the current working directory and will use the default version of
Python for the virtualenv executable in your PATH. You can change the
name of the virtual environment by setting the environment variable
VENV_NAME.
"""

from __future__ import print_function

import os
import shutil
import glob
import time
import subprocess
import sys
import re
import shlex

VERSION_PATTERN = re.compile(r'^(\d+)\.(\d+).*$')


class PythonExecutableNotFoundError(Exception):
    pass


def find_python_executable(python_major):
    # type: (int) -> str
    """
    Find the relevant python executable that is of the given python major version.
    Will test, in decreasing priority order:
    * the current Python interpreter
    * 'pythonX' executable in PATH (with X the given major version) if available
    * 'python' executable in PATH if available
    * Windows Python launcher 'py' executable in PATH if available
    Incompatible python versions for Certbot will be evicted (eg. Python < 3.5 on Windows)
    :param int python_major: the Python major version to target (2 or 3)
    :rtype: str
    :return: the relevant python executable path
    :raise RuntimeError: if no relevant python executable path could be found
    """
    python_executable_path = None

    # First try, current python executable
    if _check_version('{0}.{1}.{2}'.format(
            sys.version_info[0], sys.version_info[1], sys.version_info[2]), python_major):
        return sys.executable

    # Second try, with python executables in path
    versions_to_test = ['2.7', '2', ''] if python_major == 2 else ['3', '']
    for one_version in versions_to_test:
        try:
            one_python = 'python{0}'.format(one_version)
            output = subprocess.check_output([one_python, '--version'],
                                             universal_newlines=True, stderr=subprocess.STDOUT)
            if _check_version(output.strip().split()[1], python_major):
                return subprocess.check_output([one_python, '-c',
                                                'import sys; sys.stdout.write(sys.executable);'],
                                               universal_newlines=True)
        except (subprocess.CalledProcessError, OSError):
            pass

    # Last try, with Windows Python launcher
    try:
        env_arg = '-{0}'.format(python_major)
        output_version = subprocess.check_output(['py', env_arg, '--version'],
                                                 universal_newlines=True, stderr=subprocess.STDOUT)
        if _check_version(output_version.strip().split()[1], python_major):
            return subprocess.check_output(['py', env_arg, '-c',
                                            'import sys; sys.stdout.write(sys.executable);'],
                                           universal_newlines=True)
    except (subprocess.CalledProcessError, OSError):
        pass

    if not python_executable_path:
        raise RuntimeError('Error, no compatible Python {0} executable for Certbot could be found.'
                           .format(python_major))


def _check_version(version_str, major_version):
    search = VERSION_PATTERN.search(version_str)

    if not search:
        return False

    version = (int(search.group(1)), int(search.group(2)))

    minimal_version_supported = (2, 7)
    if major_version == 3 and os.name == 'nt':
        minimal_version_supported = (3, 5)
    elif major_version == 3:
        minimal_version_supported = (3, 4)

    if version >= minimal_version_supported:
        return True

    print('Incompatible python version for Certbot found: {0}'.format(version_str))
    return False


def subprocess_with_print(cmd, env=os.environ, shell=False):
    print('+ {0}'.format(subprocess.list2cmdline(cmd)) if isinstance(cmd, list) else cmd)
    subprocess.check_call(cmd, env=env, shell=shell)


def get_venv_bin_path(venv_path):
    python_linux = os.path.join(venv_path, 'bin/python')
    if os.path.isfile(python_linux):
        return os.path.abspath(os.path.dirname(python_linux))
    python_windows = os.path.join(venv_path, 'Scripts\\python.exe')
    if os.path.isfile(python_windows):
        return os.path.abspath(os.path.dirname(python_windows))

    raise ValueError((
        'Error, could not find python executable in venv path {0}: is it a valid venv ?'
        .format(venv_path)))


def main(venv_name, venv_args, args):
    """Creates a virtual environment and installs packages.

    :param str venv_name: The name or path at where the virtual
        environment should be created.
    :param str venv_args: Command line arguments for virtualenv
    :param str args: Command line arguments that should be given to pip
        to install packages
    """

    for path in glob.glob('*.egg-info'):
        if os.path.isdir(path):
            shutil.rmtree(path)
        else:
            os.remove(path)

    env_venv_name = os.environ.get('VENV_NAME')
    if env_venv_name:
        print('Creating venv at {0}'
              ' as specified in VENV_NAME'.format(env_venv_name))
        venv_name = env_venv_name

    if os.path.isdir(venv_name):
        os.rename(venv_name, '{0}.{1}.bak'.format(venv_name, int(time.time())))

    command = [sys.executable, '-m', 'virtualenv', '--no-site-packages', '--setuptools', venv_name]
    command.extend(shlex.split(venv_args))
    subprocess_with_print(command)

    # We execute the following commands in the context of the virtual environment, to install
    # the packages in it. To do so, we append the venv binary to the PATH that will be used for
    # these commands. With this trick, correct python executable will be selected.
    new_environ = os.environ.copy()
    new_environ['PATH'] = os.pathsep.join([get_venv_bin_path(venv_name), new_environ['PATH']])
    subprocess_with_print('python {0}'.format('./letsencrypt-auto-source/pieces/pipstrap.py'),
                          env=new_environ, shell=True)
    subprocess_with_print('python -m pip install --upgrade "setuptools>=30.3"',
                          env=new_environ, shell=True)
    subprocess_with_print('python {0} {1}'.format('./tools/pip_install.py', ' '.join(args)),
                          env=new_environ, shell=True)

    if os.path.isdir(os.path.join(venv_name, 'bin')):
        # Linux/OSX specific
        print('-------------------------------------------------------------------')
        print('Please run the following command to activate developer environment:')
        print('source {0}/bin/activate'.format(venv_name))
        print('-------------------------------------------------------------------')
    elif os.path.isdir(os.path.join(venv_name, 'Scripts')):
        # Windows specific
        print('---------------------------------------------------------------------------')
        print('Please run one of the following commands to activate developer environment:')
        print('{0}\\Scripts\\activate.bat (for Batch)'.format(venv_name))
        print('.\\{0}\\Scripts\\Activate.ps1 (for Powershell)'.format(venv_name))
        print('---------------------------------------------------------------------------')
    else:
        raise ValueError('Error, directory {0} is not a valid venv.'.format(venv_name))


if __name__ == '__main__':
    main('venv',
         '',
         sys.argv[1:])
