# Copyright (c) Microsoft Corporation. All rights reserved.
# Licensed under the MIT License. See LICENSE in the project root
# for license information.

from __future__ import absolute_import, print_function, unicode_literals

"""Python 2/3 compatibility helpers.
"""

import inspect
import itertools
import sys

from ptvsd.common import fmt


try:
    import builtins
except ImportError:
    import __builtin__ as builtins  # noqa

try:
    unicode = builtins.unicode
    bytes = builtins.str
except AttributeError:
    unicode = builtins.str
    bytes = builtins.bytes

try:
    xrange = builtins.xrange
except AttributeError:
    xrange = builtins.range

try:
    izip = itertools.izip
except AttributeError:
    izip = builtins.zip

try:
    reload = builtins.reload
except AttributeError:
    from importlib import reload  # noqa

try:
    import queue
except ImportError:
    import Queue as queue  # noqa


def force_unicode(s, encoding, errors="strict"):
    """Converts s to Unicode, using the provided encoding. If s is already Unicode,
    it is returned as is.
    """
    return s.decode(encoding, errors) if isinstance(s, bytes) else unicode(s)


def force_bytes(s, encoding, errors="strict"):
    """Converts s to bytes, using the provided encoding. If s is already bytes,
    it is returned as is.

    If errors="strict" and s is bytes, its encoding is verified by decoding it;
    UnicodeError is raised if it cannot be decoded.
    """
    if isinstance(s, unicode):
        return s.encode(encoding, errors)
    else:
        s = bytes(s)
        if errors == "strict":
            # Return value ignored - invoked solely for verification.
            s.decode(encoding, errors)
        return s


def force_str(s, encoding="ascii", errors="strict"):
    """Converts s to str (which is bytes on Python 2, and unicode on Python 3), using
    the provided encoding if necessary. If s is already str, it is returned as is.

    If errors="strict", str is bytes, and s is str, its encoding is verified by decoding
    it; UnicodeError is raised if it cannot be decoded.
    """
    return (force_bytes if str is bytes else force_unicode)(s, encoding, errors)


def force_ascii(s, errors="strict"):
    """Same as force_bytes(s, "ascii", errors)
    """
    return force_bytes(s, "ascii", errors)


def force_utf8(s, errors="strict"):
    """Same as force_bytes(s, "utf8", errors)
    """
    return force_bytes(s, "utf8", errors)


def filename(s, errors="strict"):
    """Same as force_unicode(s, sys.getfilesystemencoding(), errors)
    """
    return force_unicode(s, sys.getfilesystemencoding(), errors)


def filename_bytes(s, errors="strict"):
    """Same as force_bytes(s, sys.getfilesystemencoding(), errors)
    """
    return force_bytes(s, sys.getfilesystemencoding(), errors)


def filename_str(s, errors="strict"):
    """Same as force_str(s, sys.getfilesystemencoding(), errors)
    """
    return force_str(s, sys.getfilesystemencoding(), errors)


def nameof(obj, quote=False):
    """Returns the most descriptive name of a Python module, class, or function,
    as a Unicode string

    If quote=True, name is quoted with repr().

    Best-effort, but guaranteed to not fail - always returns something.
    """

    try:
        name = obj.__qualname__
    except Exception:
        try:
            name = obj.__name__
        except Exception:
            # Fall back to raw repr(), and skip quoting.
            try:
                name = repr(obj)
            except Exception:
                return "<unknown>"
            else:
                quote = False

    if quote:
        try:
            name = repr(name)
        except Exception:
            pass

    return force_unicode(name, "utf-8", "replace")


def unicode_repr(obj):
    """Like repr(), but guarantees that the result is Unicode even on Python 2.
    """
    return force_unicode(repr(obj), "ascii")


def srcnameof(obj):
    """Returns the most descriptive name of a Python module, class, or function,
    including source information (filename and linenumber), if available.

    Best-effort, but guaranteed to not fail - always returns something.
    """

    name = nameof(obj, quote=True)

    # Get the source information if possible.
    try:
        src_file = filename(inspect.getsourcefile(obj), "replace")
    except Exception:
        pass
    else:
        name += fmt(" (file {0!r}", src_file)
        try:
            _, src_lineno = inspect.getsourcelines(obj)
        except Exception:
            pass
        else:
            name += fmt(", line {0}", src_lineno)
        name += ")"

    return name
