# fsck.py - functions for checking repository consistency
#
# 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 collections
import json
import os
import re


def _clean(config, repo, filename, msg='unused file or directory'):
    removed = False
    if config.clean:
        try:
            repo.backend.remove(filename)
            removed = True
        except EnvironmentError:
            import traceback
            print(traceback.format_exc())
    print('%s: %s%s' % (filename, msg, ' (REMOVED)' if removed else ''))


def _filter(extension, sequence):
    """Split the list into a list that has the items that begin with
    prefix and one with the other items."""
    l1, l2 = [], []
    extension = '.%s.' % extension
    for filename in sequence:
        if extension in filename:
            l1.append(filename)
        else:
            l2.append(filename)
    return l1, l2


def check_keys(config, repo):
    """Go over the files in the keys directory."""
    # get list of files
    files = list(repo.backend.listdir('keys'))
    # check presence and validity of passphrase file
    if 'keys/passphrase.gpg' not in files:
        pass  # ignore
    else:
        files.remove('keys/passphrase.gpg')
        # try to read the passphrase file
        from filters import GnuPGKeyEncryption
        try:
            with repo.read_file(
                    'keys/passphrase', encryption=GnuPGKeyEncryption()) as f:
                passphrase = str(f.read()).strip()
        except IOError:
            import traceback
            print(traceback.format_exc())
    # list superfluous files
    for filename in files:
        _clean(config, repo, filename, 'unknown file or directory')


def check_archive(config, repo, archive, files, found_archives):
    # TODO: check that file names contain recognised compression and
    #       encryption extensions
    # split files in archives, json files and others
    archives, other = _filter('tar', files)
    jsons, other = _filter('json', other)
    # check that there is exactly one tar file
    if len(archives) < 1:
        for filename in files:
            _clean(config, repo, filename,
                   'corresponding archive file missing')
        return  # skip further checks on this archive
    elif len(archives) > 1:
        for filename in archives:
            print('%s: duplicate archive file' % filename)
    # mark archive as found
    found_archives[archive] = 0
    # check that there is exactly one JSON file
    if len(jsons) < 1:
        for filename in files:
            print('%s: corresponding JSON file missing' % filename)
        # TODO: alternatively try to reconstruct the JSON from the archive
    elif len(jsons) > 1:
        for filename in jsons:
            print('%s: duplicate JSON file' % filename)
    if jsons:
        try:
            for meta in repo.read_fileslist('archives/%s.json' % archive):
                if not meta.get('path'):
                    raise ValueError('path property missing')
        except (StopIteration, ValueError, EnvironmentError):
            import traceback
            print(traceback.format_exc())
            print('%s: corrupt' % jsons[0])
    # check remaining files
    for filename in other:
        _clean(config, repo, filename, 'unknown file or directory')
    # TODO: consider unpacking the tar file (only if some option is
    #       specified and check that the information matches the JSON)


def check_archives(config, repo, found_archives):
    """Check the consistency of the archives directory."""
    # go over all found files in archives directory
    archives = collections.defaultdict(list)
    for filename in repo.backend.listdir('archives'):
        m = re.match(
            r'archives/([0-9a-zA-Z]{8}-[0-9a-zA-Z]{8})\.(json|tar)(\..*)?$',
            filename)
        if m:
            archives[m.group(1)].append(filename)
        else:
            _clean(config, repo, filename, 'unknown file or directory')
    # see if each archive has two files: one archive and one json
    for archive, files in archives.items():
        check_archive(config, repo, archive, files, found_archives)


def check_unused_archives(config, repo, found_archives):
    """Check archives directory for unused archievs ."""
    # go over archive files
    for filename in repo.backend.listdir('archives'):
        m = re.match(
            r'archives/([0-9a-zA-Z]{8}-[0-9a-zA-Z]{8})\.(json|tar)(\..*)?$',
            filename)
        if m:
            if found_archives.get(m.group(1), 0) == 0:
                _clean(config, repo, filename, 'unused file')


def check_backup(config, repo, backup, found_archives):
    """Check the validity of the specified backup."""
    files = list(
        os.path.basename(f) for f in repo.backend.listdir('backups/' + backup))
    # check for presence of restore.sh
    if 'restore.sh' not in files:
        print('backups/%s/restore.sh: missing' % backup)
    else:
        # check contents of restore.sh (first line hashbang, last line exit 0)
        files.remove('restore.sh')
    # check for presence of info.json
    info_files = [x for x in files if x.startswith('info.json')]
    if not info_files:
        print('backups/%s/info.json: missing' % backup)
    elif len(info_files) > 1:
        for x in info_files:
            print('backups/%s/%s: duplicate info file' % (backup, x))
            files.remove(x)
    else:
        files.remove(info_files[0])
    # read info.json
    info = {'archives': []}
    if info_files:
        try:
            with repo.read_file('backups/%s/info.json' % backup) as f:
                info = json.load(f)
        except (IOError, ValueError) as e:
            print('backups/%s/%s: invalid or currupt: %s' % (
                backup, info_files[0], e))
    # check that all required extractlists are present
    if 'extractlists' not in info:
        if info_files:
            print('backups/%s/%s: extractlist info missing' % (
                backup, info_files[0]))
        # just remove all extractlist from file list
        for archive in info['archives']:
            files = [x for x in files if not x.startswith('%s.list' % archive)]
    else:
        # check that each extractlist is present
        for archive in info['extractlists']:
            elists = [x for x in files if x.startswith('%s.list' % archive)]
            if not elists:
                print('backups/%s/%s.list: missing' % (backup, archive))
            elif len(elists) > 1:
                for filename in elists:
                    print('backups/%s/%s: duplicate extractlist file' % (
                        backup, filename))
                    files.remove(filename)
            else:
                files.remove(elists[0])
    # check that all required archives are present and update found_archives
    for archive in info['archives']:
        if archive not in found_archives:
            print('backups/%s: archive %s missing' % (backup, archive))
        else:
            found_archives[archive] += 1
    # check for presence of files.json
    files_files = [x for x in files if x.startswith('files.json')]
    if not files_files:
        print('backups/%s/files.json: missing' % backup)
    elif len(files_files) > 1:
        for x in files_files:
            print('backups/%s/%s: duplicate file list' % (backup, x))
            files.remove(x)
    else:
        files.remove(files_files[0])
    # read files.json
    if files_files:
        try:
            for meta in repo.read_fileslist('backups/%s/files.json' % backup):
                if not meta.get('path'):
                    raise ValueError('path property missing')
        except (StopIteration, ValueError, EnvironmentError):
            import traceback
            print(traceback.format_exc())
            print('%s: corrupt' % filename)
    # check remaining files
    for filename in files:
        filename = 'backups/%s/%s' % (backup, filename)
        _clean(config, repo, filename, 'unknown file or directory')


def check_backups(config, repo, found_archives):
    """Go over the list of backups in the repository."""
    for filename in repo.backend.listdir('backups'):
        check_backup(config, repo, os.path.basename(filename), found_archives)


def fsck(config, repo):
    """Check consistency of the repository."""
    # get contents of top-level directory
    top = list(repo.backend.listdir(''))
    archives = False
    backups = False
    keys = False
    # check that archives is present and is a directory
    if 'archives' not in top:
        print('archives: directory missing')
    elif not repo.backend.isdir('archives'):
        print('archives: is not a directory')
    else:
        archives = True
        top.remove('archives')
    # check that backups is present and is a directory
    if 'backups' not in top:
        print('backups: directory missing')
    elif not repo.backend.isdir('backups'):
        print('backups: is not a directory')
    else:
        backups = True
        top.remove('backups')
    # check that keys is present and is a directory
    if 'keys' not in top:
        pass  # ignore: perhaps also pass result to archives and backups test to give an error if encryption is used
    elif not repo.backend.isdir('keys'):
        print('keys: is not a directory')
    else:
        # TODO: try to open key file
        # TODO: use key to see if every encrypted file can be decrypted using this key
        keys = True
        top.remove('keys')
    # check presence and validity of uuid file
    if 'uuid' not in top:
        print('uuid: missing')
    elif repo.backend.isdir('uuid'):
        print('uuid: is not a file')
    else:
        top.remove('uuid')
        try:
            with repo.read_file('uuid') as f:
                uuid = str(f.read()).strip()
            # check uuid validity
            if not re.match(r'^[0-9a-z]{8,16}$', uuid):
                print('uuid: invalid')
        except IOError:
            import traceback
            print(traceback.format_exc())
    # list superfluous toplevel files
    for filename in top:
        _clean(config, repo, filename, 'unknown file or directory')
    # recurse into keys, archives and backups directories
    if keys:
        check_keys(config, repo)
    found_archives = {}
    if archives:
        check_archives(config, repo, found_archives)
    if backups:
        check_backups(config, repo, found_archives)
    if archives and backups:
        check_unused_archives(config, repo, found_archives)
    # print some statistics:
    print '%d archives found' % len(found_archives)
    counts = collections.defaultdict(int)
    for archive, count in found_archives.items():
        counts[count] += 1
    for use, archives in counts.items():
        print '%d archives used %d times' % (archives, use)