FreedomBox/plinth/module_loader.py

# SPDX-License-Identifier: AGPL-3.0-or-later
"""
Discover, load and manage FreedomBox applications.
"""

import collections
import importlib
import logging
import pathlib
import re

import django

from plinth import cfg
from plinth.signals import pre_module_loading

logger = logging.getLogger(__name__)

loaded_modules = collections.OrderedDict()
_modules_to_load = None


def include_urls():
    """Include the URLs of the modules into main Django project."""
    for module_import_path in get_modules_to_load():
        module_name = module_import_path.split('.')[-1]
        _include_module_urls(module_import_path, module_name)


def load_modules():
    """
    Read names of enabled modules in modules/enabled directory and
    import them from modules directory.
    """
    pre_module_loading.send_robust(sender="module_loader")
    for module_import_path in get_modules_to_load():
        module_name = module_import_path.split('.')[-1]
        try:
            loaded_modules[module_name] = importlib.import_module(
                module_import_path)
        except Exception as exception:
            logger.exception('Could not import %s: %s', module_import_path,
                             exception)
            if cfg.develop:
                raise


def _include_module_urls(module_import_path, module_name):
    """Include the module's URLs in global project URLs list"""
    from plinth import urls
    url_module = module_import_path + '.urls'
    try:
        urls.urlpatterns += [
            django.urls.re_path(r'',
                                django.urls.include((url_module, module_name)))
        ]
    except ImportError:
        logger.debug('No URLs for %s', module_name)
        if cfg.develop:
            raise


def _get_modules_enabled_paths():
    """Return list of paths from which enabled modules list must be read."""
    return [
        pathlib.Path('/usr/share/freedombox/modules-enabled/'),
        pathlib.Path('/etc/plinth/modules-enabled/'),  # For compatibility
        pathlib.Path('/etc/freedombox/modules-enabled/'),
    ]


def _get_modules_enabled_files_to_read():
    """Return the list of files containing modules import paths."""
    module_files = {}
    for path in _get_modules_enabled_paths():
        directory = pathlib.Path(path)
        files = list(directory.glob('*'))
        for file_ in files:
            # Omit hidden or backup files
            if file_.name.startswith('.') or '.dpkg' in file_.name:
                continue

            if file_.is_symlink() and str(file_.resolve()) == '/dev/null':
                module_files.pop(file_.name, None)
                continue

            module_files[file_.name] = file_

    if module_files:
        return module_files.values()

    # 'make build install' has not been executed yet. Pickup files to load from
    # local module directories.
    directory = pathlib.Path(__file__).parent
    glob_pattern = 'modules/*/data/usr/share/freedombox/modules-enabled/*'
    return list(directory.glob(glob_pattern))


def get_modules_to_load():
    """Get the list of modules to be loaded"""
    global _modules_to_load
    if _modules_to_load is not None:
        return _modules_to_load

    modules = []
    for file_ in _get_modules_enabled_files_to_read():
        module = _read_module_import_paths_from_file(file_)
        if module:
            modules.append(module)

    _modules_to_load = modules
    return modules


def get_module_import_path(module_name: str) -> str:
    """Return the import path for a module."""
    import_path_file = None
    for path in _get_modules_enabled_paths():
        file_ = path / module_name
        if file_.exists():
            import_path_file = file_

        if file_.is_symlink() and str(file_.resolve()) == '/dev/null':
            import_path_file = None

    if not import_path_file:
        # 'make build install' has not been executed yet. Pickup files to load
        # from local module directories.
        directory = pathlib.Path(__file__).parent
        import_path_file = (directory /
                            f'modules/{module_name}/data/usr/share/'
                            f'freedombox/modules-enabled/{module_name}')

    if not import_path_file:
        raise ValueError('Unknown module')

    import_path = _read_module_import_paths_from_file(import_path_file)
    if not import_path:
        raise ValueError('Module disabled')

    return import_path


def _read_module_import_paths_from_file(file_path: pathlib.Path) -> str | None:
    """Read a module's import path from a file."""
    with file_path.open() as file_handle:
        for line in file_handle:
            line = re.sub('#.*', '', line)
            line = line.strip()
            if line:
                return line

    return None