#!/bin/bash

err() { printf 'error: %b\n' "$*" 1>&2; exit 1; }
usage() {
	cat <<-EOF
	backup-dvd [options] [commands]

	Options:
	 -i <input dev>      Defaults to ${dev}
	 -o <output dir>     Defaults to ${out}
	 -n <volume name>    Defaults to volume on disk

	Commands:
	 --errors   Image the raw disc first w/ddrescue
	 --backup   Back up the disc
	 --modify   Tweak runtime settings (needs -n)
	 --mkiso    Create an iso (needs -n)

	If no commands are specified, then all are run.
	EOF
	exit ${1:-0}
}

dev=/dev/cdrom
out=${PWD}
vol=

unset doit_{backup,modify,mkiso}
doit_errors=false

eval set -- `getopt -l errors,backup,modify,mkiso -- hi:n:o: "$@"`
while [[ -n $1 ]] ; do
	case $1 in
		-h) usage;;
		-i) dev=$2; shift 2;;
		-o) out=$2; shift 2;;
		-n) vol=$2; shift 2;;

		--errors) doit_errors=true; shift;;
		--backup) doit_backup=true; shift;;
		--modify) doit_modify=true; shift;;
		--mkiso)  doit_mkiso=true;  shift;;

		--) shift; break;;
		-*) usage 1;;
		*)  usage 2; break;;
	esac
done

doit_all() {
	: ${doit_backup:=$1}
	: ${doit_modify:=$1}
	: ${doit_mkiso:=$1}
}
if [[ -z ${doit_backup}${doit_modify}${doit_mkiso} ]] ; then
	doit_all true
else
	doit_all false
fi

# iso-info		mkisofs
Application=	# -A
Preparer=		# -p
Publisher=		# -publisher
System=			# -sysid
Volume=${vol}	# -V
Volume_Set=		# -volset

if ${doit_backup} ; then
	if [[ -z ${Volume} ]] ; then
		info=$(iso-info ${dev}) || exit 1

		eval $(echo "${info}" | awk -F: '
			(NF > 1 && $1 !~ /image/) {
				sub(/ *$/, "", $1);
				sub(/ /, "_", $1);
				sub(/^ */, "", $2);
				print $1 "=\"" $2 "\"";
		}')
	fi

	if [[ -z ${Volume} ]] ; then
		echo "Unable to parse Volume out of ISO"
		iso-info ${dev}
	fi

	for v in Application Preparer Publisher System Volume Volume_Set ; do
		echo "${v}='${!v}'"
	done > "${out}/.${Volume}.vars.sh"
else
	[[ -z ${Volume} ]] && err "Need to specify -n with --modify/--mkiso"
	. "${out}/.${Volume}.vars.sh" || exit 1
fi

e() {
	for a ; do
		[[ ${a} == *" "* || ${#a} == 0 ]] && fmt='"%s"' || fmt='%s'
		printf "${fmt} " "${a}"
	done
	echo
	"$@"
}

#
# Mirror the disc w/ddrescue which tolerates errors.
#
raw_read_dvd() {
	echo "Imaging disc"
	local raw=".${Volume}.raw"
	local log="${raw}.log"
	local opts=(
		-v -b 2048 ${dev} "${raw}" "${log}"
	)
	ddrescue -p -n "${opts[@]}"
	ddrescue -d -r 3 "${opts[@]}"
	ddrescue -d -r 3 -R "${opts[@]}"
	dev=${raw}
}

#
# Backup the disc.
#
backup_dvd() {
	echo "Backing up: ${Volume}"
	local opts=(
		-i ${dev}
		-o "${out}"
		-n "${Volume}"
	)
	sync
	if ! e dvdbackup -M "${opts[@]}" ; then
		e dvdbackup -F "${opts[@]}" || exit 1
	fi
	sync
}

#
# Modify some of the runtime settings.
#
bytes_get() {
	local pfx='0x' sep
	while [[ $# -gt 3 ]]; do
		case $1 in
		"-p") pfx=$2;;
		"-s") sep=$2;;
		*) break;;
		esac
		shift 2
	done
	printf '%b' "${pfx}"

	local file=$1 off=$2 num=${3:-1}
	hexdump -v -n ${num} -s $((${off})) -e "1/1 \"%02x${sep}\"" "${file}"
}
bytes_set() {
	local file=$1 off=$2
	shift 2
	(for b; do printf "\x${b#0x}"; done) | \
		dd of="${file}" \
			bs=1 seek=$((${off})) \
			conv=notrunc status=none
}
dvdsec() {
	# DVDs have sectors of 2048 bytes (2^11).
	local file=$1 off=$2 num=${3:-4}
	echo $(( $(bytes_get "${file}" "${off}" "${num}") << 11 ))
}

_check_ifo() {
	# Back up the .IFO files before we edit them.
	local ifo=$1 magic=$2
	[[ -e ${ifo} ]] || return 1

	if [[ $(bytes_get "${ifo}" 0 12) != "0x${magic}" ]] ; then
		echo "not a VMG IFO file: ${ifo}"
		return 1
	fi
	if [[ ! -e ${ifo}.bak ]] ; then
		cp -a "${ifo}" "${ifo}.bak"
	fi

	return 0
}

check_changes() {
	[[ -e ifodump ]] || return 0

	local file=$1
	./ifodump -f "${file}.bak" > "${file}.bak.dmp"
	./ifodump -f "${file}" > "${file}.dmp"
	vapier-diff "${file}.bak.dmp" "${file}.dmp" | sed -e 1d -e 2d > "${file}.diff"
	local out=$(
		grep '^[+-]' "${file}.diff" | \
			grep -v \
				-e '^-VMG Category:.*' \
				-e '^+VMG Category: 00000000 (Region Code=ff)' \
				-e '^[-+].*Title playback type:' \
				-e '^-.*Title or time play:1' \
				-e '^+.*Title or time play:0' \
				-e '^-Prohibited user operations:' \
				-e '^+Prohibited user operations: Angle Change, $' \
				-e '^+Prohibited user operations: None$' \
			| egrep -v -e '^[-+]([0-9a-f]{2} )+$'
	)
	rm "${file}".{{,bak.}dmp,diff}
	if [[ -z ${out} ]] ; then
		return 0
	else
		echo "error in ifo modification:"
		echo "${out}"
		return 1
	fi
}

process_pgci() {
	# http://dvdnav.mplayerhq.hu/dvdinfo/pgc.html
	local file=$1 pgci_off=$2 indent=$3
	local num_pgcs p pgc_off off

	num_pgcs=$(bytes_get "${file}" ${pgci_off} 2)
	for (( p = 0; p < num_pgcs; ++p )) ; do
		pgc_off=$((
			pgci_off +
			$(bytes_get "${file}" $(( pgci_off + 8 + 8 * p + 4 )) 4)
		))
		off=$(( pgc_off + 8 ))
		pgc_puo=$(bytes_get "${file}" ${off} 4)
		printf '%bpgc #%2i @ %#06x: %s: ' "${indent}" ${p} ${vmgm_pgc_off} ${pgc_puo}
		new_pgc_puo=$(( pgc_puo & (1 << 22) )) # Keep angle field.
		if [[ ${pgc_puo} -ne ${new_pgc_puo} ]] ; then
			bytes_set "${file}" ${off} 0 $(printf '%x' $(( new_pgc_puo >> 16 ))) 0 0
			echo "cleared"
		else
			echo "nothing to do"
		fi
	done
}

process_pgci_ut() {
	# http://dvdnav.mplayerhq.hu/dvdinfo/ifo_vts.html#pgciut
	local file=$1 pgci_ut_off=$2
	local num_langs l off

	num_langs=$(bytes_get "${file}" ${pgci_ut_off} 2)
	for (( l = 0; l < num_langs; ++l )) ; do
		off=$((
			pgci_ut_off +
			$(bytes_get "${file}" $(( pgci_ut_off + 8 + 8 * l + 4 )) 4)
		))
		printf '\tclearing lang #%i @ %#06x\n' ${l} ${off}
		process_pgci "${file}" ${off} '\t\t'
	done
}

process_vmgi() {
	# Back up the .IFO files before we edit them.
	local vmgi=$1
	_check_ifo "${vmgi}" "445644564944454f2d564d47" || return 1

	echo "${vmgi}"

	# Clear the region code.
	# http://dvdnav.mplayerhq.hu/dvdinfo/ifo.html
	# 0x23 - region code restrict byte - set to 0x00 for region free.
	echo "clearing region code"
	bytes_set "${vmgi}" 0x23 0x00

	# Clear all Prohibited User Operations (PUOs) in TT_SRPT (Uop1 & Uop0).
	# http://dvdnav.mplayerhq.hu/dvdinfo/ifo_vmg.html
	echo "clearing PUOs in TT_SRPT"
	tt_srpt_sec=$(dvdsec "${vmgi}" 0xC4)

	num_titles=$(bytes_get "${vmgi}" ${tt_srpt_sec} 2)
	for (( t = 0; t < num_titles; ++t )) ; do
		off=$(( tt_srpt_sec + 8 + (t * 12) ))
		printf "\ttitle type #%2i @ %#06x: " "${t}" "${off}"
		title_type=$(bytes_get "${vmgi}" ${off} 1)
		uop0=$(( title_type & 1 ))
		uop1=$(( title_type & 2 ))
		printf "%s (uop1:%i uop0:%i): " ${title_type} ${uop1} ${uop0}
		new_title_type=$(( title_type & ~3 ))
		if [[ ${title_type} -ne ${new_title_type} ]] ; then
			bytes_set "${vmgi}" ${off} $(printf '%x' ${new_title_type})
			echo "cleared"
		else
			echo "nothing to do"
		fi
	done

	# Clear all the PUOs in the PGCs.  But Preserve the angle bit.
	#   Note: Removal of the angle PUO can cause certain standalone players to
	#   display the "angle" icon during playback. Removal of the angle PUO
	#   whilst permitted is therefore not recommended.
	# http://dvdnav.mplayerhq.hu/dvdinfo/uops.html
	#fp_pgc_addr=$(bytes_get "${vmgi}" 0x84 4)
	#num_pgcs=$(bytes_get "${vmgi}" $(( fp_pgc_sec + 1 )) 1)
	echo "clearing PUOs in PGCs"
	vmgm_pgci_ut_sec=$(dvdsec "${vmgi}" 0xC8)
	process_pgci_ut "${vmgi}" ${vmgm_pgci_ut_sec}
}

process_vtsi() {
	# Back up the .IFO files before we edit them.
	local vtsi=$1
	_check_ifo "${vtsi}" "445644564944454f2d565453" || return 1

	echo "${vtsi}"

	echo "clearing PUOs in PGCs"

	vts_pgci_sec=$(dvdsec "${vtsi}" 0xCC)
	process_pgci "${vtsi}" ${vts_pgci_sec} '\t'

	vtsm_pgci_ut_sec=$(dvdsec "${vtsi}" 0xD0)
	process_pgci_ut "${vtsi}" ${vtsm_pgci_ut_sec}
}

modify_dvd() {
	local out_vts_dir="${out}/${Volume}/VIDEO_TS"
	local vmgi vtsi

	if ${doit_errors} ; then
		echo "skipping modifications due to possible errors in files"
		return
	fi

	for vmgi in "${out_vts_dir}"/VIDEO_TS.{IFO,BUP} ; do
		process_vmgi "${vmgi}"
		check_changes "${vmgi}" || exit 1
	done

	for vtsi in "${out_vts_dir}"/VTS_??_?.{IFO,BUP} ; do
		process_vtsi "${vtsi}"
		check_changes "${vtsi}" || exit 1
	done
}

#
# Finally, create a new iso.
#
mkiso_dvd() {
	set -- mkisofs -quiet -dvd-video -no-bak \
		-A "${Application}" \
		-p "${Preparer}" \
		-publisher "${Publisher}" \
		-sysid "${System}" \
		-V "${Volume}" \
		-volset "${Volume_Set}" \
		-o "${Volume}.iso" "${Volume}"
	sh="${out}/.${Volume}.sh"
	(
	echo "#!/bin/sh"
	echo "cd '${out}' || exit 1"
	echo ". './.${Volume}.vars.sh'"
	printf 'set -- '
	printf '%q ' "$@"
	echo
	echo 'echo "$@"; exec "$@"'
	) > "${sh}"
	chmod a+x "${sh}"
	"${sh}" || exit
	sync
	md5sum "${out}/${Volume}.iso" > "${out}/${Volume}.md5"

	du -h "${out}/${Volume}.iso"
	sudo chattr +i "${out}/${Volume}.iso"
	sync
}

${doit_errors} && raw_read_dvd
${doit_backup} && backup_dvd
${doit_modify} && modify_dvd
${doit_mkiso} && mkiso_dvd

${doit_backup} && eject
exit 0