#!/usr/bin/python3
# -*- coding: utf-8 -*-
# Copyright (C) 2020 Patrik Dufresne<info@patrikdufresne.com>
#
# 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 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 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/>.
#
#
#
# rdiff-backup-delete
#
# Deletes files and directories from a rdiff-backup repository, including the
# current mirror and all its history. Also remove any reference from the
# metadata.
#

import os
import sys

import getopt
import gzip
import re
import stat
import struct

PY2 = sys.version_info < (3,)
PY26 = sys.version_info > (2, 6) and sys.version_info < (2, 7)
PY3 = sys.version_info > (3,)

# List of suffixes for increments
SUFFIXES = [b".missing", b".snapshot.gz", b".snapshot",
            b".diff.gz", b".data.gz", b".data", b".dir", b".diff"]


def _bytes(value):
    if isinstance(value, bytes if PY3 else str):
        return value
    if PY3:
        return value.encode('utf8', errors='surrogateescape')
    else:
        return value.encode('utf8')


def _str(value):
    if isinstance(value, str if PY3 else unicode):
        return value
    if PY26:
        return value.decode('utf-8')
    else:
        return value.decode('utf-8', errors='replace')


def _print_usage(error_message=None):
    if error_message:
        print(error_message)
    print("Usage: %s [OPTION]... PATH\n\n"
        "Delete PATH from a rdiff-backup repository including the current \n"
        "mirror and all its history.\n\n"
        "-h, --help\n\n"
        "        Display this help text and exit\n\n"
        "-d, --dry-run\n\n"
        "        Run the script without doing modifications to the repository.\n\n"
        "PATH\n\n"
        "        A relative or absolute path to be deleted. This path must be\n"
        "        inside a rdiff-backup repository.\n"
        % (sys.argv[0],))
    sys.exit(1 if error_message else 0)


def _parse_options():
    """
    Used to parse the arguments.
    """
    # Support environment variable
    try:
        optlist, args = getopt.getopt(
            sys.argv[1:], "hd", ["help", "dry-run"],
        )
    except getopt.GetoptError as e:
        _print_usage("fatal: bad command line: " + str(e))
    dry_run = False
    for opt, arg in optlist:
        if opt in ["-h", "--help"]:
            _print_usage()
        elif opt in ["-d", "--dry-run"]:
            dry_run = True
        else:
            _print_usage("fatal: invalid arguments: %s" % opt)

    # Make sure we get a folder or a file to be deleted.
    if len(args) == 0:
        _print_usage('fatal: missing arguments')
    elif len(args) > 1:
        _print_usage('fatal: too many arguments')

    # Check the repository.
    dir = path = os.path.abspath(_bytes(args[0]))
    while dir != b'/':
        rdiff_backup_data = os.path.join(dir, b'rdiff-backup-data')
        if os.path.isdir(rdiff_backup_data):
            relpath = os.path.relpath(path, start=dir)
            if relpath == b'rdiff-backup-data':
                sys.exit("fatal: can't delete rdiff-backup-data")
            return dir, relpath, dry_run
        # Continue with parent directory.
        dir = os.path.dirname(dir)

    sys.exit("fatal: not a rdiff-backup repository (or any parent up to mount point /)")


def _filename_from_increment(file):
    """
    Return the filename from an increment entry.
    e.g.: Revisions.2014-11-05T16:04:30-05:00.dir
    return "Revision"
    """
    for suffix in SUFFIXES:
        if file.endswith(suffix):
            with_suffix = file[:-len(suffix)]
            return with_suffix.rsplit(b".", 1)[0]
    return None


def _remove_from_metadata(repopath, file, dry_run):
    """
    This function is used to remove the repo path from the given `file` metadata.
    """
    if os.path.basename(file).startswith(b'file_statistics'):
        start_marker = b''

        def matches(line):
            path = line.rsplit(b' ', 4)[0]
            return path == repopath.metaquote or path.startswith(repopath.metaquote + b'/')

    elif os.path.basename(file).startswith(b'mirror_metadata'):
        start_marker = b'File '

        def matches(line):
            return line == b'File ' + repopath.metaquote + b'\n' or line.startswith(b'File ' + repopath.metaquote + b'/')

    elif (os.path.basename(file).startswith(b'extended_attributes')
          or os.path.basename(file).startswith(b'access_control_lists')):
        start_marker = b'# file: '

        def matches(line):
            return line == b'# file: ' + repopath.aclquote + b'\n' or line.startswith(b'# file: ' + repopath.aclquote + b'/')

    else:
        return

    print('removing entries `%s` from %s' % (_str(repopath.relpath), _str(file)))
    _open = gzip.open if file.endswith(b'.gz') else open
    input = _open(file, 'rb')
    tmp_file = os.path.join(os.path.dirname(file), b'.tmp.' + os.path.basename(file))
    output = _open(tmp_file, 'wb')
    try:
        line = input.readline()
        while line:
            if line.startswith(start_marker) and matches(line):
                line = input.readline()
                while line and not line.startswith(start_marker):
                    # Special case to handle longfilename
                    if line.startswith(b'  AlternateIncrementName ') or line.startswith(b'  AlternateMirrorName '):
                        name = line.strip(b'\n').rsplit(b' ', 1)[1]
                        path = os.path.join(repopath.repo.long_filename_data, name)
                        _remove_increments(path, dry_run)
                    line = input.readline()
            else:
                output.write(line)
                line = input.readline()
    finally:
        input.close()
        output.close()
    if not dry_run:
        os.rename(tmp_file, file)
    else:
        os.remove(tmp_file)


def _remove_increments(path, dry_run):
    """
    Remove all <path>.*.<suffixes> 
    """
    # If the increment is a directory, remove it and all it's content.
    _rmtree(path, dry_run)

    # Then let find all the increment entries (.missing, .dir, .gz, .diff.gz)
    dir = os.path.dirname(path)
    fn = os.path.basename(path)

    if os.path.isdir(dir):
        for p in os.listdir(dir):
            file = os.path.join(dir, p)
            if not os.path.isdir(file) and fn == _filename_from_increment(p):
                # Remove the increment entry
                print('deleting increments `%s`' % (_str(file),))
                if not dry_run:
                    os.remove(file)


def _rmtree(path, dry_run):
    """
    Custom implementation of shutil.rmtree() to support deletion of symlink.
    """
    try:
        mode = os.lstat(path).st_mode
    except os.error:
        mode = 0
    if stat.S_ISDIR(mode):
        names = []
        names = os.listdir(path)
        for name in names:
            fullname = os.path.join(path, name)
            _rmtree(fullname, dry_run)
        if not dry_run:
            os.rmdir(path)
    elif mode:
        if not dry_run:
            os.remove(path)


def _unquote(name):
        """Remove quote (;000) from the given name."""
        assert isinstance(name, bytes)

        # This function just gives back the original text if it can decode it
        def unquoted_char(match):
            """For each ;000 return the corresponding byte."""
            if not len(match.group()) == 4:
                return match.group
            try:
                return bytes([int(match.group()[1:])])
            except:
                return match.group

        # Remove quote using regex
        return re.sub(b";[0-9]{3}", unquoted_char, name, re.S)


def _acl_quote(s):
    """Quote filename for ACL usages."""
    # Table mapping for meta_quote and meta_unquote
    _safe = b'0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!"#$%&\'()*+,-./:;<>?@[]^_`{|}~'
    _meta_quote_map = {}
    for i in range(1, 256):
        c = struct.pack('B', i)
        k = i if PY3 else c
        if c in _safe:
            _meta_quote_map[k] = c
        else:
            _meta_quote_map[k] = '\\{0:03o}'.format(i).encode('ascii')
    return b''.join(map(_meta_quote_map.__getitem__, s))


class Repo():
    """
    Represent the rediff-backup repository.
    
    rdiff_backup_data: <root>/rdiff-backup-data/
    long_filename_data: <root>/rdiff-backup-data/long_filename_data/
    """

    def __init__(self, root):
        self.root = root
        self.rdiff_backup_data = os.path.join(self.root, b'rdiff-backup-data')
        self.long_filename_data = os.path.join(self.rdiff_backup_data, b'long_filename_data')

    def is_lock(self):
        """
        Try to lock the repository. Raise an error if the repository
        is already locked by another process.
        """
        # Check if the repository has multiple current_mirror.
        count = len([x for x in os.listdir(self.rdiff_backup_data) if x.startswith(b'current_mirror.')])
        return count > 1


class RepoPath():
    """
    Object used to provide all the variation of the same path with different escaping.
    
    root: absolute location of the rdiff-backup repository
    relpath: relative path to the file of folder to be deleted
    abspath: absolute path to the file or folder to be delete (may not exists)
    metaquote: unquoted relative path (;000 replace by bytes) with quoted \
    aclquote: quoted relative path (bytes converted into \000)
    increments: <root>/rdiff-backup-data/increments/<relpath>
    """

    def __init__(self, root, relpath):
        assert root
        assert isinstance(root, bytes if PY3 else str)
        assert os.path.isdir(root)
        assert os.path.isdir(os.path.join(root, b'rdiff-backup-data'))
        assert relpath
        assert isinstance(relpath, bytes if PY3 else str)
        assert relpath != b'rdiff-backup-data'
        self.repo = Repo(root)
        self.relpath = relpath
        self.metaquote = _unquote(self.relpath).replace(b'\\', b'\\\\')
        self.aclquote = _acl_quote(self.relpath)

        # Return the absolute location of this path on the filesystem
        self.abspath = os.path.join(self.repo.root, self.relpath)
        self.increments = os.path.join(self.repo.rdiff_backup_data, b'increments', self.relpath)


def main():
    # Parse the arguments.
    # root maybe None
    root, relpath, dry_run = _parse_options()
    repopath = RepoPath(root, relpath)
    if repopath.repo.is_lock():
        sys.exit('fail to acquired repository lock. A backup may be running.')
    
    # Check if the repository is "locked"
    print("start deleting path `%s` from repository %s" % (_str(relpath), _str(root)))
    if dry_run:
        print("running in dry-run mode")

    # Remove any entries from metadata files: file_statistics, mirror_metadata, extended_attributes, access_control_lists
    dir = repopath.repo.rdiff_backup_data
    for f in os.listdir(dir):
        _remove_from_metadata(repopath, os.path.join(dir, f), dry_run)

    print('deleting directory `%s` recursively' % (_str(repopath.abspath),))
    _rmtree(repopath.abspath, dry_run)

    # Then let find all the increment entries (.missing, .dir, .gz, .diff.gz)
    _remove_increments(repopath.increments, dry_run)
    print('done')


# Call main if this script is call directly.
if __name__ == "__main__":
    main()