#!/usr/bin/env bash

# Copyright (c) 2023 Joshua Lee Ockert <torstenvl@gmail.com>
#
# THIS WORK IS PROVIDED "AS IS" WITH NO WARRANTY OF ANY KIND. THE IMPLIED
# WARRANTIES OF MERCHANTABILITY, FITNESS, NON-INFRINGEMENT, AND TITLE ARE
# EXPRESSLY DISCLAIMED. NO AUTHOR SHALL BE LIABLE UNDER ANY THEORY OF LAW
# FOR ANY DAMAGES OF ANY KIND RESULTING FROM THE USE OF THIS WORK.
#
# Permission to use, copy, modify, and/or distribute this work for any
# purpose is hereby granted, provided this notice appears in all copies.


function dispusage() {
  if [ ${#1} -gt 0 ]; then
    printf "%s\n\n" "${1}"
  fi
  echo "\
TIME MACHINE IMPORT

USAGE

    ${0} <backup drive>

DESCRIPTION

    Time Machine Importer attempts to inherit the backup history of a backup
    drive. If the backup drive is not paired to the current computer, Time
    Machine Importer will attempt to pair the drive with the current computer
    by modifying the model, MAC address, and UUID/UDID reflected in the
    metadata of the backup drive.

    The backup drive should be specified by disk or volume name (or path) or
    the mount point of the backup drive. For example:
        - ${0} /dev/disk1s1
        - ${0} /Volumes/TMBACKUP

    While some additional heuristics may assist in identifying a backup drive
    that is specified in other ways, they are untested and not guaranteed
    to work correctly.
"
}


############################################################################
##                   PARSE & MAKE SENSE OF COMMAND LINE                   ##
############################################################################
if [ ! $# -eq 1 ]; then
  dispusage "Invalid number of arguments" && exit
fi

## IF USER PROVIDED A VALID DEVICE, VOLUME NAME, OR MOUNT POINT, USE THAT
diskutil list "${1}" > /dev/null 2>&1 
if [[ $? -eq 0 ]]; then
    MOUNTPOINT=`diskutil info ${1} | grep "Mount Point:" | sed 's/^ *Mount Point: *\(.*\)$/\1/'`
    if [ "${MOUNTPOINT}" == "" ]; then
        dispusage "No mount point for specified device ${1}. Perhaps it isn't mounted?" && exit
    fi

    if [ ! -d "${MOUNTPOINT}/Backups.backupdb/" ]; then
        dispusage "No Backups.backupdb directory found at ${MOUNTPOINT}/Backups.backupdb/" && exit
    fi 

    BACKUPPATH=`find ${MOUNTPOINT}/Backups.backupdb -type d -maxdepth 1 -xattrname com.apple.backupd.HostUUID -print -quit`
    if [ "${BACKUPPATH}" == "" ]; then
        dispusage "No suitable backups within ${MOUNTPOINT}/Backups.backupdb!" && exit
    fi
    SPECIFIED="${1}"

## OTHERWISE, THE USER MAY HAVE PROVIDED A BACKUPS.BACKUPDB PATH
elif [[ -d "${1}" ]] && [[ $(stat -f %R ${1}) =~ Backups.backupdb$ ]]; then
    BACKUPPATH=`find $(stat -f %R ${1}) -type d -mindepth 1 -maxdepth 1 -xattrname com.apple.backupd.HostUUID -print -quit`
    if [ "${BACKUPPATH}" == "" ]; then
        dispusage "No suitable backups within $(stat -f %R ${1})!" && exit
    fi
    SPECIFIED=$(stat -f %R ${1})

## OR MAYBE EVEN THE DIRECTORY WITHIN IT
elif [[ -d "${1}" ]] && [[ $(stat -f %R ${1}) =~ Backups.backupdb\/.+$ ]]; then
    BACKUPPATH=`find $(stat -f %R ${1}) -type d -maxdepth 0 -xattrname com.apple.backupd.HostUUID -print -quit`
    if [ "${BACKUPPATH}" == "" ]; then
        dispusage "No suitable backups at $(stat -f %R ${1})!" && exit
    fi
    SPECIFIED=$(stat -f %R ${1})

## OTHERWISE WE'RE SCREWED
else
    dispusage "${1} is not a valid device, volume, or Backups.backupdb path." && exit
fi


############################################################################
##                    GET NECESSARY SYSTEM INFORMATION                    ##
############################################################################
MODEL=`ioreg -d2 -k IOPlatformUUID | awk -F\" '/"model"/{print $(NF-1)}'`
UUID=`ioreg -d2 -k IOPlatformUUID | awk -F\" '/"IOPlatformUUID"/{print $(NF-1)}'`
MAC=`ifconfig en0 | awk '/ether/{print $2}'`
#UUIDHEX=`printf '%s\0' ${UUID} | xxd -p -c37`
#MACHEX=`printf '%s\0' ${MAC} | xxd -p`

KERNELVER=`uname -a | sed 's/.*Version \([0-9][0-9]*\).*/\1/g'`
if [ $KERNELVER -lt 20 ]; then
  SIMONSAYS="sudo /System/Library/Extensions/TMSafetyNet.kext/Contents/Helpers/bypass"
else
  SIMONSAYS="sudo"
fi


############################################################################
##                       CONFIRM ACTION INFORMATION                       ##
############################################################################
printf "\n\
Specified Backup:  %s\n\
Backup Location:   %s\n\
Computer Model:    %s\n\
Host UUID:         %s\n\
MAC Address:       %s\n\n" "${SPECIFIED}" "${BACKUPPATH}" "${MODEL}" "${UUID}" "${MAC}"

printf "This backup drive is currently matched to the following computer:\n"
printf "    ModelID:     %s\n"   "$(xattr -p 'com.apple.backupd.ModelID' "${BACKUPPATH}")"
printf "    MAC Address: %s\n"   "$(xattr -p 'com.apple.backupd.BackupMachineAddress' "${BACKUPPATH}")"
printf "    Host UUID:   %s\n\n" "$(xattr -p 'com.apple.backupd.HostUUID' "${BACKUPPATH}")"

printf "\
Preparing to run the following commands:\n\
    %s xattr -w 'com.apple.backupd.ModelID'              \"%-36s\" \"%s\"\n\
    %s xattr -w 'com.apple.backupd.BackupMachineAddress' \"%-36s\" \"%s\"\n\
    %s xattr -w 'com.apple.backupd.HostUUID'             \"%-36s\" \"%s\"\n\
    %s tmutil inheritbackup \"%s\"\n\
    \n" "${SIMONSAYS}"  "${MODEL}"  "${BACKUPPATH}" \
        "${SIMONSAYS}"  "${MAC}"    "${BACKUPPATH}" \
        "${SIMONSAYS}"  "${UUID}"   "${BACKUPPATH}" \
        "${SIMONSAYS}"  "${BACKUPPATH}"

if [ ! "$(basename "${BACKUPPATH}")" == "$(scutil --get ComputerName)" ]; then
    printf "#############################################################################\n"
    printf "##            W A R N I N G     W A R N I N G     W A R N I N G            ##\n"
    printf "#############################################################################\n"
    printf "\n"
    printf "The Backup Location DOES NOT MATCH your computer name.\n"
    printf "\n"
    printf "    Backup Location:        %s\n" "${BACKUPPATH}"
    printf "    Backup Computer Name:   %s\n" "$(basename "${BACKUPPATH}")"
    printf "    Current Computer Name:  %s\n" "$(scutil --get ComputerName)"
    printf "\n"
    printf "Only proceed if you are very certain of what you're doing!\n"
    printf "Even if successful, the Time Machine restore UI will be adversely affected.\n"
else
    printf "Does everything look right?\n"
fi    


select response in "Import Time Machine backup" "ABORT ABORT ABORT!"; do
    if [ "${response}" == "Import Time Machine backup" ]; then
        "${SIMONSAYS}" xattr -w 'com.apple.backupd.ModelID'              "${MODEL}" "${BACKUPPATH}"
        "${SIMONSAYS}" xattr -w 'com.apple.backupd.BackupMachineAddress' "${MAC}"   "${BACKUPPATH}"
        "${SIMONSAYS}" xattr -w 'com.apple.backupd.HostUUID'             "${UUID}"  "${BACKUPPATH}"
        "${SIMONSAYS}" tmutil inheritbackup "${BACKUPPATH}"
        if [ ! $? -eq 0 ]; then
            printf "\nOperation failed. Backup history not imported.\n\n"
        else
            printf "\nOperation completed.\n\n"
            printf "This backup drive has been matched to the following computer:\n"
            printf "    ModelID:     %s\n"   "$(xattr -p 'com.apple.backupd.ModelID' "${BACKUPPATH}")"
            printf "    MAC Address: %s\n"   "$(xattr -p 'com.apple.backupd.BackupMachineAddress' "${BACKUPPATH}")"
            printf "    Host UUID:   %s\n\n" "$(xattr -p 'com.apple.backupd.HostUUID' "${BACKUPPATH}")"
        fi
        break
    else
        printf "\nOperation aborted. No action has been taken.\n\n"
        break
    fi
done