#!/usr/bin/env python
"""
Convert the conda environment.yml to the pip requirements-dev.txt,
or check that they have the same packages (for the CI)

Usage:

    Generate `requirements-dev.txt`
    $ ./conda_to_pip

    Compare and fail (exit status != 0) if `requirements-dev.txt` has not been
    generated with this script:
    $ ./conda_to_pip --compare
"""
import argparse
import os
import re
import sys
import yaml


EXCLUDE = {'python=3'}
RENAME = {'pytables': 'tables'}


def conda_package_to_pip(package):
    """
    Convert a conda package to its pip equivalent.

    In most cases they are the same, those are the exceptions:
    - Packages that should be excluded (in `EXCLUDE`)
    - Packages that should be renamed (in `RENAME`)
    - A package requiring a specific version, in conda is defined with a single
      equal (e.g. ``pandas=1.0``) and in pip with two (e.g. ``pandas==1.0``)
    """
    if package in EXCLUDE:
        return

    package = re.sub('(?<=[^<>])=', '==', package).strip()
    for compare in ('<=', '>=', '=='):
        if compare not in package:
            continue

        pkg, version = package.split(compare)

        if pkg in RENAME:
            return ''.join((RENAME[pkg], compare, version))

        break

    return package


def main(conda_fname, pip_fname, compare=False):
    """
    Generate the pip dependencies file from the conda file, or compare that
    they are synchronized (``compare=True``).

    Parameters
    ----------
    conda_fname : str
        Path to the conda file with dependencies (e.g. `environment.yml`).
    pip_fname : str
        Path to the pip file with dependencies (e.g. `requirements-dev.txt`).
    compare : bool, default False
        Whether to generate the pip file (``False``) or to compare if the
        pip file has been generated with this script and the last version
        of the conda file (``True``).

    Returns
    -------
    bool
        True if the comparison fails, False otherwise
    """
    with open(conda_fname) as conda_fd:
        deps = yaml.safe_load(conda_fd)['dependencies']

    pip_content = '\n'.join(filter(None, map(conda_package_to_pip, deps)))

    if compare:
        with open(pip_fname) as pip_fd:
            return pip_content != pip_fd.read()
    else:
        with open(pip_fname, 'w') as pip_fd:
            pip_fd.write(pip_content)
        return False


if __name__ == '__main__':
    argparser = argparse.ArgumentParser(
        description='convert (or compare) conda file to pip')
    argparser.add_argument('--compare',
                           action='store_true',
                           help='compare whether the two files are equivalent')
    args = argparser.parse_args()

    repo_path = os.path.dirname(os.path.abspath(os.path.dirname(__file__)))
    res = main(os.path.join(repo_path, 'environment.yml'),
               os.path.join(repo_path, 'requirements-dev.txt'),
               compare=args.compare)
    if res:
        sys.stderr.write('`requirements-dev.txt` has to be generated with '
                         '`{}` after `environment.yml` is modified.\n'.format(
                             sys.argv[0]))
    sys.exit(res)
