# Copyright (C) 2013 Intra2net AG
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation; either version 3 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 Lesser General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see
# <http://www.gnu.org/licenses/lgpl-3.0.html>


import os, unittest, hashlib, string
import random

from deltatar import crypto

import sys

BLOCK_SIZE = 8096

def new_volume_handler(tarobj, base_name, volume_number, encryption=None):
    '''
    Handles the new volumes
    '''
    volume_path = "%s.%d" % (base_name, volume_number)
    tarobj.open_volume(volume_path, encryption=encryption)

def make_new_encryption_volume_handler(encryption):
    '''
    Handles the new volumes using the right crypto context.
    '''
    return lambda tarobj, base_name, volume_number: \
        new_volume_handler (tarobj, base_name, volume_number,
                            encryption=encryption)

def closing_new_volume_handler(tarobj, base_name, volume_number):
    '''
    Handles the new volumes
    '''
    volume_path = "%s.%d" % (base_name, volume_number)
    tarobj.fileobj.close()
    tarobj.open_volume(volume_path)

class BaseTest(unittest.TestCase):
    """
    Test concatenated compression in tarfiles
    """

    def tearDown(self):
        '''
        Remove temporal files created by unit tests
        '''
        os.system("rm -rf big big2 small small2 sample.* pdtcrypt-object-*.bin")

    def create_file_low_entropy(self, path, length):
        '''
        Creates a file with some gibberish inside, returning the md5sum of that
        file. File path and length are specified as function arguments.
        '''
        data = string.ascii_lowercase + string.digits + "\n"

        # determine how often need to repeat data and how much part of data is
        # left in the end to fill file up to length
        n_blocks, remainder = divmod(length, len(data))
        with open(path, 'w') as write_handle:
            for _ in range(n_blocks):
                write_handle.write(data)
            write_handle.write(data[:remainder])
        return self.md5sum(path)


    def create_file_high_entropy(self, path, length):
        """
        Create a file with quality random content to counteract compression.
        """
        fd = os.open (path, os.O_WRONLY | os.O_CREAT | os.O_TRUNC)
        try:
            p = 0
            while p < length:
                todo = min (length - p, BLOCK_SIZE)
                os.write (fd, os.urandom (todo))
                p += todo
        finally:
            os.close (fd)
        assert p == length
        return self.md5sum (path)


    def create_file(self, path, length, random=False):
        '''
        Creates a file with some gibberish inside, returning the md5sum of that
        file. File path and length are specified as function arguments.
        '''
        if random is True:
            return self.create_file_high_entropy (path, length)

        return self.create_file_low_entropy (path, length)


    def create_symlink(self, linkname, path):
        os.symlink(linkname, path)
        return self.md5sum(path, linkname=linkname)

    def md5sum(self, filename, linkname=None):
        '''
        Returns the md5sum of a file specified by its filename/path or, if
        ``linkname`` is specified, the hash of both paths (for symlinks).
        '''
        md5 = hashlib.md5()
        if linkname is None:
            with open(filename,'rb') as f:
                for chunk in iter(lambda: f.read(128*md5.block_size), b''):
                    md5.update(chunk)
        else: # symlink; hash paths
            md5.update(filename.encode("UTF-8"))
            md5.update(linkname.encode("UTF-8"))
        return md5.hexdigest()