#!/usr/bin/env python

import os
import sys
import argparse
import pip
import six
import subprocess

from importlib import import_module

def main():
    usage = """./tools/provision

Creates a Python virtualenv. Its Python version is equal to
the Python version this command is executed with."""
    parser = argparse.ArgumentParser(usage=usage)
    parser.parse_args()

    base_dir = os.path.abspath(os.path.join(__file__, '..', '..'))
    python_version = '.'.join(str(num) for num in sys.version_info[0:3])
    python_interpreter = os.path.abspath(sys.executable)
    venv_name = 'zulip-api-py{}-venv'.format(python_version)

    venv_dir = os.path.join(base_dir, venv_name)
    if not os.path.isdir(venv_dir):
        if subprocess.call(['virtualenv', '-p', python_interpreter, venv_dir]):
            raise OSError("The command `virtualenv -p {} {}` failed. Virtualenv not created!"
                          .format(python_interpreter, venv_dir))
        else:
            print("New virtualenv created.")
    else:
        print("Virtualenv already exists.")

    if os.path.isdir(os.path.join(venv_dir, 'Scripts')):
        # POSIX compatibility layer and Linux environment emulation for Windows
        # Virtual uses /Scripts instead of /bin on Windows.
        # Read https://virtualenv.pypa.io/en/stable/userguide/
        venv_exec_dir = 'Scripts'
    else:
        venv_exec_dir = 'bin'

    # In order to install all required packages for the venv, we need to activate it. Since
    # the activation script sets environmental variables, it needs to be executed inline with
    # `import_module`.
    activate_module_dir = os.path.abspath(os.path.join(venv_dir, venv_exec_dir))
    sys.path.append(activate_module_dir)
    import_module('activate_this')

    # In order to install all required packages for the venv, `pip` needs to be executed by
    # the venv's Python interpreter. `--prefix venv_dir` ensures that all modules are installed
    # in the right place.
    if subprocess.call([os.path.join(venv_dir, venv_exec_dir, 'pip'),
                        'install', '--prefix', venv_dir, '-r', os.path.join(base_dir, 'requirements.txt')]):
        raise OSError("The command `pip install -r {}` failed. Dependencies not installed!"
                      .format(os.path.join(base_dir, 'requirements.txt')))

    print("Success!  Run `source {}` to activate virtualenv.".format(
        os.path.join(base_dir, venv_dir, venv_exec_dir, 'activate')))

if __name__ == '__main__':
    main()