#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Copyright 2014-2015 Canonical Limited.
#
# This file is part of charm-helpers.
#
# charm-helpers is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License version 3 as
# published by the Free Software Foundation.
#
# charm-helpers 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 Lesser General Public License
# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.

import io
import os

__author__ = 'Jorge Niedbalski R. <jorge.niedbalski@canonical.com>'


class Fstab(io.FileIO):
    """This class extends file in order to implement a file reader/writer
    for file `/etc/fstab`
    """

    class Entry(object):
        """Entry class represents a non-comment line on the `/etc/fstab` file
        """
        def __init__(self, device, mountpoint, filesystem,
                     options, d=0, p=0):
            self.device = device
            self.mountpoint = mountpoint
            self.filesystem = filesystem

            if not options:
                options = "defaults"

            self.options = options
            self.d = int(d)
            self.p = int(p)

        def __eq__(self, o):
            return str(self) == str(o)

        def __str__(self):
            return "{} {} {} {} {} {}".format(self.device,
                                              self.mountpoint,
                                              self.filesystem,
                                              self.options,
                                              self.d,
                                              self.p)

    DEFAULT_PATH = os.path.join(os.path.sep, 'etc', 'fstab')

    def __init__(self, path=None):
        if path:
            self._path = path
        else:
            self._path = self.DEFAULT_PATH
        super(Fstab, self).__init__(self._path, 'rb+')

    def _hydrate_entry(self, line):
        # NOTE: use split with no arguments to split on any
        #       whitespace including tabs
        return Fstab.Entry(*filter(
            lambda x: x not in ('', None),
            line.strip("\n").split()))

    @property
    def entries(self):
        self.seek(0)
        for line in self.readlines():
            line = line.decode('us-ascii')
            try:
                if line.strip() and not line.strip().startswith("#"):
                    yield self._hydrate_entry(line)
            except ValueError:
                pass

    def get_entry_by_attr(self, attr, value):
        for entry in self.entries:
            e_attr = getattr(entry, attr)
            if e_attr == value:
                return entry
        return None

    def add_entry(self, entry):
        if self.get_entry_by_attr('device', entry.device):
            return False

        self.write((str(entry) + '\n').encode('us-ascii'))
        self.truncate()
        return entry

    def remove_entry(self, entry):
        self.seek(0)

        lines = [l.decode('us-ascii') for l in self.readlines()]

        found = False
        for index, line in enumerate(lines):
            if line.strip() and not line.strip().startswith("#"):
                if self._hydrate_entry(line) == entry:
                    found = True
                    break

        if not found:
            return False

        lines.remove(line)

        self.seek(0)
        self.write(''.join(lines).encode('us-ascii'))
        self.truncate()
        return True

    @classmethod
    def remove_by_mountpoint(cls, mountpoint, path=None):
        fstab = cls(path=path)
        entry = fstab.get_entry_by_attr('mountpoint', mountpoint)
        if entry:
            return fstab.remove_entry(entry)
        return False

    @classmethod
    def add(cls, device, mountpoint, filesystem, options=None, path=None):
        return cls(path=path).add_entry(Fstab.Entry(device,
                                                    mountpoint, filesystem,
                                                    options=options))