python-tldp/tldp/typeguesser.py

#! /usr/bin/python
# -*- coding: utf8 -*-

from __future__ import absolute_import, division, print_function

import os
import inspect

from .utils import logger, makefh
from . import doctypes


def listDoctypes():
    kdt = list()
    for name, member in inspect.getmembers(doctypes, inspect.isclass):
        logger.debug("Located class %s (%r).", name, member)
        kdt.append(member)
    logger.debug("Capable of handling %s document classes.", len(kdt))
    return kdt


def guess(thing):
    try:
        f = makefh(thing)
    except TypeError:
        return None

    stem, ext = os.path.splitext(f.name)
    if not ext:
        logger.debug("%s no file extension, skipping %s.", stem, ext)
        return None

    possible = [t for t in knowndoctypes if ext in t.extensions]
    logger.debug("Possible:  %r", possible)
    if not possible:
        logger.debug("%s unknown extension %s.", stem, ext)
        return None

    if len(possible) == 1:
        doctype = possible.pop()
        return doctype

    # -- for this extension, multiple document types, probably SGML, XML
    #
    logger.debug("%s multiple possible doctypes for extension %s on file %s.",
                 stem, ext, f.name)
    for doctype in possible:
        logger.debug("%s extension %s could be %s.", stem, ext, doctype)

    guesses = list()
    for doctype in possible:
        sindex = doctype.signatureLocation(f)
        if sindex is not None:
            guesses.append((sindex, doctype))

    if not guesses:
        logger.warning("%s no matching signature found for %s.",
                       stem, f.name)
        return None
    if len(guesses) == 1:
        _, doctype = guesses.pop()
        return doctype

    # -- OK, this is unusual; we still found multiple document type
    #    signatures.  Seems rare but unlikely, so we should choose the
    #    first signature in the file as the more likely document type.
    #
    guesses.sort()
    logger.info("%s multiple doctype guesses for file %s", stem, f.name)
    for sindex, doctype in guesses:
        logger.info("%s could be %s (sig at pos %s)", stem, doctype, sindex)
    logger.info("%s going to guess %s for %s", stem, doctype, f.name)
    _, doctype = guesses.pop(0)
    return doctype


knowndoctypes = listDoctypes()
knownextensions = set()
for x in knowndoctypes:
    knownextensions.update(x.extensions)

#
# -- end of file