# Copyright (C) 2006 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Utilities for distinguishing binary files from text files."""

from itertools import chain

from .errors import BinaryFile
from .iterablefile import IterableFile
from .osutils import file_iterator


def text_file(input):
    """Produce a file iterator that is guaranteed to be text, without seeking.
    BinaryFile is raised if the file contains a NUL in the first 1024 bytes.
    """
    first_chunk = input.read(1024)
    if b"\x00" in first_chunk:
        raise BinaryFile()
    return IterableFile(chain((first_chunk,), file_iterator(input)))


def check_text_lines(lines):
    """Raise BinaryFile if the supplied lines contain NULs.
    Only the first 1024 characters are checked.
    """
    f = IterableFile(lines)
    if b"\x00" in f.read(1024):
        raise BinaryFile()


def check_text_path(path):
    """Check whether the supplied path is a text, not binary file.
    Raise BinaryFile if a NUL occurs in the first 1024 bytes.
    """
    with open(path, "rb") as f:
        text_file(f)