# filters.py - conversion filters for compression and encryption
#
# Copyright (C) 2015 Arthur de Jong
#
# 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 St, Fifth Floor, Boston, MA  02110-1301 USA
#
# The files produced as output from the software do not automatically fall
# under the copyright of the software, unless explicitly stated otherwise.

import os
import subprocess


class Reader(object):

    def __init__(self, cmd, fileobj):
        self.cmdline = ' '.join(cmd)
        self.fileobj = fileobj
        self.proc = subprocess.Popen(
            cmd, universal_newlines=False, stdin=fileobj,
            stdout=subprocess.PIPE, stderr=subprocess.PIPE)

    def close(self):
        # complete command
        (stdout, stderr) = self.proc.communicate(None)
        self.fileobj.close()
        # FIXME: check stderr
        if self.proc.returncode:
            print(stderr)
            raise EnvironmentError('%s failed' % self.cmdline)

    def __getattr__(self, attr):
        return getattr(self.proc.stdout, attr)

    def __iter__(self):
        return self.proc.stdout.__iter__()

    def __enter__(self):
        return self

    def __exit__(self, type, value, traceback):
        self.close()


class Writer(object):

    def __init__(self, cmd, fileobj):
        self.cmdline = ' '.join(cmd)
        self.fileobj = fileobj
        self.proc = subprocess.Popen(
            cmd, universal_newlines=False, stdin=subprocess.PIPE,
            stdout=fileobj, stderr=subprocess.PIPE)

    def close(self):
        # complete command
        (stdout, stderr) = self.proc.communicate(None)
        self.fileobj.close()
        # FIXME: check stderr
        if self.proc.returncode:
            print(stderr)
            raise EnvironmentError('%s failed' % self.cmdline)

    def __getattr__(self, attr):
        return getattr(self.proc.stdin, attr)


    def __enter__(self):
        return self

    def __exit__(self, type, value, traceback):
        self.close()


class Filter(object):

    extension = ''

    def rename(self, fname):
        if self.extension:
            return '%s.%s' % (fname, self.extension)
        return fname


class GzipCompression(Filter):

    extension = 'gz'
    restore_cmd = 'gzip -dc'

    def reader(self, fileobj):
        return Reader(['gzip', '-dc'], fileobj)

    def writer(self, fileobj):
        return Writer(['gzip', '-c', '-n', '-9'], fileobj)


class Bzip2Compression(Filter):

    extension = 'bz2'
    restore_cmd = 'bzip2 -dc'

    def reader(self, fileobj):
        return Reader(['bzip2', '-dc'], fileobj)

    def writer(self, fileobj):
        return Writer(['bzip2', '-c', '-9'], fileobj)


class XZCompression(Filter):

    extension = 'xz'
    restore_cmd = 'xz -dc'

    def reader(self, fileobj):
        return Reader(['xz', '-dc'], fileobj)

    def writer(self, fileobj):
        return Writer(['xz', '-zc'], fileobj)


class NoEncryption(Filter):

    restore_cmd = 'cat'

    def reader(self, fileobj):
        return fileobj

    def writer(self, fileobj):
        return fileobj


class GnuPGEncryption(Filter):

    extension = 'gpg'
    restore_cmd = 'gpg -q --batch --no-use-agent ' + \
                  '--passphrase-file "$EXTMPDIR"/passphrase -d'

    def __init__(self, repo):
        self.repo = repo

    def reader(self, fileobj):
        infd, outfd = os.pipe()
        os.write(outfd, self.repo.get_passphrase() + '\n')
        os.close(outfd)
        f = Reader([
            'gpg', '--batch', '--no-use-agent', '-q',
            '--passphrase-fd', str(infd), '--no-textmode', '-d'],
            fileobj)
        os.close(infd)
        return f

    def writer(self, fileobj):
        infd, outfd = os.pipe()
        os.write(outfd, (self.repo.get_passphrase() + '\n').encode('ascii'))
        os.close(outfd)
        f = Writer([
            'gpg', '--batch', '--symmetric', '--cipher-algo', 'AES256', '-q',
            '--compress-algo', 'none', '--passphrase-fd', str(infd),
            '--no-textmode'],
            fileobj)
        os.close(infd)
        return f


class GnuPGKeyEncryption(Filter):

    extension = 'gpg'
    restore_cmd = 'gpg -d'

    def __init__(self, keys=()):
        self.keys = keys

    def reader(self, fileobj):
        return Reader(['gpg', '-d', '-q'], fileobj)

    def writer(self, fileobj):
        args = ['gpg', '--batch', '-q', '--encrypt', '--trust-model', 'always']
        for key in self.keys:
            args.extend(['--recipient', key])
        return Writer(args, fileobj)