from __future__ import absolute_import

import marshal
import os
import re
import sys
import warnings

from . import _imp as imp

try:
    unicode
except NameError:
    unicode = str


if sys.version_info[0] == 2:
    from StringIO import StringIO
    from StringIO import StringIO as BytesIO

else:
    from io import BytesIO, StringIO


def imp_find_module(name, path=None):
    """
    same as imp.find_module, but handles dotted names
    """
    names = name.split(".")
    if path is not None:
        if isinstance(path, (str, unicode)):
            path = [os.path.realpath(path)]
    for name in names:
        result = imp.find_module(name, path)
        if result[0] is not None:
            result[0].close()
        path = [result[1]]
    return result


def _check_importer_for_path(name, path_item):
    try:
        importer = sys.path_importer_cache[path_item]
    except KeyError:
        for path_hook in sys.path_hooks:
            try:
                importer = path_hook(path_item)
                break
            except ImportError:
                pass
        else:
            importer = None
        sys.path_importer_cache.setdefault(path_item, importer)

    if importer is None:
        try:
            return imp.find_module(name, [path_item])
        except ImportError:
            return None

    if hasattr(importer, "find_module"):
        return importer.find_module(name)
    else:
        spec = importer.find_spec(name)
        if spec is None:
            return None
        return spec.loader


def imp_walk(name):
    """
    yields namepart, tuple_or_importer for each path item

    raise ImportError if a name can not be found.
    """
    warnings.warn(
        "imp_walk will be removed in a future version", DeprecationWarning, stacklevel=2
    )

    if name in sys.builtin_module_names:
        yield name, (None, None, ("", "", imp.C_BUILTIN))
        return
    paths = sys.path
    res = None
    for namepart in name.split("."):
        for path_item in paths:
            res = _check_importer_for_path(namepart, path_item)
            if hasattr(res, "load_module"):
                if res.path.endswith(".py") or res.path.endswith(".pyw"):
                    fp = StringIO(res.get_source(namepart))
                    res = (fp, res.path, (".py", "rU", imp.PY_SOURCE))
                elif res.path.endswith(".pyc") or res.path.endswith(".pyo"):
                    co = res.get_code(namepart)
                    fp = BytesIO(imp.get_magic() + b"\0\0\0\0" + marshal.dumps(co))
                    res = (fp, res.path, (".pyc", "rb", imp.PY_COMPILED))

                else:
                    res = (
                        None,
                        res.path,
                        (os.path.splitext(res.path)[-1], "rb", imp.C_EXTENSION),
                    )

                break
            elif isinstance(res, tuple):
                break
        else:
            break

        yield namepart, res
        paths = [os.path.join(path_item, namepart)]
    else:
        return

    raise ImportError("No module named %s" % (name,))


cookie_re = re.compile(rb"coding[:=]\s*([-\w.]+)")
if sys.version_info[0] == 2:
    default_encoding = "ascii"
else:
    default_encoding = "utf-8"


def guess_encoding(fp):
    for _i in range(2):
        ln = fp.readline()

        m = cookie_re.search(ln)
        if m is not None:
            return m.group(1).decode("ascii")

    return default_encoding
