mat2/src/parser_factory.py

import os
import mimetypes
import importlib
import pkgutil

from . import abstract

from typing import TypeVar

T = TypeVar('T', bound='abstract.AbstractParser')

# This loads every parser in a dynamic way
for module_loader, name, ispkg in pkgutil.walk_packages('.src'):
    if not name.startswith('src.'):
        continue
    elif name == 'src.abstract':
        continue
    importlib.import_module(name)


def _get_parsers() -> list:
    """ Get all our parsers!"""
    def __get_parsers(cls):
        return cls.__subclasses__() + \
            [g for s in cls.__subclasses__() for g in __get_parsers(s)]
    return __get_parsers(abstract.AbstractParser)


def get_parser(filename: str) -> (T, str):
    # A set of extension that aren't supported, despite matching a known mimetype
    unknown_extensions = set(['bat', 'c', 'h', 'ksh', 'pl', 'txt', 'asc',
        'text', 'pot', 'brf', 'srt', 'rdf', 'wsdl', 'xpdl', 'xsl', 'xsd'])
    _, extension = os.path.splitext(filename)
    if extension in unknown_extensions:
        return None, mtype

    mtype, _ = mimetypes.guess_type(filename)
    for c in _get_parsers():
        if mtype in c.mimetypes:
            try:
                return c(filename), mtype
            except ValueError:
                return None, mtype
    return None, mtype