'''Script to perform import of each module given to %%py_check_import

'''

import argparse

import importlib

import fnmatch

import os

import re

import site

import sys

from contextlib import contextmanager

from pathlib import Path

def read_modules_files(file_paths):

    '''Read module names from the files (modules must be newline separated).

    Return the module names list or, if no files were provided, an empty list.

    '''

    if not file_paths:

        return []

    modules = []

    for file in file_paths:

        file_contents = file.read_text()

        modules.extend(file_contents.split())

    return modules

def read_modules_from_cli(argv):

    '''Read module names from command-line arguments (space or comma separated).

    Return the module names list.

    '''

    if not argv:

        return []

    # %%py3_check_import allows to separate module list with comma or whitespace,

    # we need to unify the output to a list of particular elements

    modules_as_str = ' '.join(argv)

    modules = re.split(r'[\s,]+', modules_as_str)

    # Because of shell expansion in some less typical cases it may happen

    # that a trailing space will occur at the end of the list.

    # Remove the empty items from the list before passing it further

    modules = [m for m in modules if m]

    return modules

def filter_top_level_modules_only(modules):

    '''Filter out entries with nested modules (containing dot) ie. 'foo.bar'.

    Return the list of top-level modules.

    '''

    return [module for module in modules if '.' not in module]

def any_match(text, globs):

    '''Return True if any of given globs fnmatchcase's the given text.'''

    return any(fnmatch.fnmatchcase(text, g) for g in globs)

def exclude_unwanted_module_globs(globs, modules):

    '''Filter out entries which match the either of the globs given as argv.

    Return the list of filtered modules.

    '''

    return [m for m in modules if not any_match(m, globs)]

def read_modules_from_all_args(args):

    '''Return a joined list of modules from all given command-line arguments.

    '''

    modules = read_modules_files(args.filename)

    modules.extend(read_modules_from_cli(args.modules))

    if args.exclude:

        modules = exclude_unwanted_module_globs(args.exclude, modules)

    if args.top_level:

        modules = filter_top_level_modules_only(modules)

    # Error when someone accidentally managed to filter out everything

    if len(modules) == 0:

        raise ValueError('No modules to check were left')

    return modules

def import_modules(modules):

    '''Procedure to perform import check for each module name from the given list of modules.

    '''

    for module in modules:

        print('Check import:', module, file=sys.stderr)

        importlib.import_module(module)

def argparser():

    parser = argparse.ArgumentParser(

        description='Generate list of all importable modules for import check.'

    )

    parser.add_argument(

        'modules', nargs='*',

        help=('Add modules to check the import (space or comma separated).'),

    )

    parser.add_argument(

        '-f', '--filename', action='append', type=Path,

        help='Add importable module names list from file.',

    )

    parser.add_argument(

        '-t', '--top-level', action='store_true',

        help='Check only top-level modules.',

    )

    parser.add_argument(

        '-e', '--exclude', action='append',

        help='Provide modules globs to be excluded from the check.',

    )

    return parser

@contextmanager

def remove_unwanteds_from_sys_path():

    '''Remove cwd and this script's parent from sys.path for the import test.

    Bring the original contents back after import is done (or failed)

    '''

    cwd_absolute = Path.cwd().absolute()

    this_file_parent = Path(__file__).parent.absolute()

    old_sys_path = list(sys.path)

    for path in old_sys_path:

        if Path(path).absolute() in (cwd_absolute, this_file_parent):

            sys.path.remove(path)

    try:

        yield

    finally:

        sys.path = old_sys_path

def addsitedirs_from_environ():

    '''Load directories from the _PYTHONSITE environment variable (separated by :)

    and load the ones already present in sys.path via site.addsitedir()

    to handle .pth files in them.

    This is needed to properly import old-style namespace packages with nspkg.pth files.

    See https://bugzilla.redhat.com/2018551 for a more detailed rationale.'''

    for path in os.getenv('_PYTHONSITE', '').split(':'):

        if path in sys.path:

            site.addsitedir(path)

def main(argv=None):

    cli_args = argparser().parse_args(argv)

    if not cli_args.modules and not cli_args.filename:

        raise ValueError('No modules to check were provided')

    modules = read_modules_from_all_args(cli_args)

    with remove_unwanteds_from_sys_path():

        addsitedirs_from_environ()

        import_modules(modules)

if __name__ == '__main__':

    main()