#!/bin/bash

###############################################################################

mode_can_dump=false
can_device=vcan0
mode_file=true
input_file=-

while [ -n "$1" ]; do
    case "$1" in
	-h|--help)
		echo -e "Usage:	$0 [-h|--help] [-i|--input <file>|-]"
		echo -e "	[-c|--can [-d|--can-device <device>]]"
		exit	0
		;;		
	-i|--input)
		mode_file=true
		input_file="$2"
		shift
		;;
	-c|--can)
		mode_can_dump=true
		;;
	-d|--can-device)
		mode_can_dump=true
		can_device="$2"
		shift
		;;
	*)
		echo -e "$0: error: invalid command line argument near '$1'." >> /dev/stderr
		exit	1
		;;
    esac
    shift
done

###############################################################################

function wideenc_decode()
{
 local	out=0
 local	hex=0x0$1
 local	a0=$((hex))
 local	hex=0x0$2
 local	a1=$((hex))
 local	hex=0x0$3
 local	a2=$((hex))
 local	hex=0x0$4
 local	a3=$((hex))
 local	hex=0x0$5
 local	a4=$((hex))

 if [ $((a0&0xC0)) == 0 ]; then
	out=$a0
 elif [ $((a0&0xE0)) == $((0x40)) ]; then
	out=$(( ((a0&0x1F)<< 7) | (a1&0x7F) ))
 elif [ $((a0&0xF0)) == $((0x60)) ]; then
	out=$(( ((a0&0x0F)<<14) | ((a1&0x7F)<< 7) | (a2&0x7F) ))
 elif [ $((a0&0xF8)) == $((0x70)) ]; then
	out=$(( ((a0&0x07)<<21) | ((a1&0x7F)<<14) | ((a2&0x7F)<< 7) | (a3&0x7F) ))
 elif [ $((a0&0xFC)) == $((0x78)) ]; then
	out=$(( ((a0&0x03)<<28) | ((a1&0x7F)<<21) | ((a2&0x7F)<<14) | ((a3&0x7F)<< 7) | (a4&0x7F) ))
 else
	out=0
 fi
 echo	$out
}

function wideenc_length()
{
 local	hex=0x0$1
 local	a0=$((hex))

 if [ $((a0&0xC0)) == 0 ]; then
	echo	1
 elif [ $((a0&0xE0)) == $((0x40)) ]; then
	echo	2
 elif [ $((a0&0xF0)) == $((0x60)) ]; then
	echo	3
 elif [ $((a0&0xF8)) == $((0x70)) ]; then
	echo	4
 elif [ $((a0&0xFC)) == $((0x78)) ]; then
	echo	5
 else
	echo	1
 fi 
}

###############################################################################

GETF_DK_PORT_DEFAULT=0x33
GETF_PORT_FLAG_SIZE_OFFSET_FILENAME=0x01
GETF_PORT_FLAG_INODE_POSITION=0x02
GETF_PORT_FLAG_REED_SOLOMON=0x04

if $mode_can_dump; then

	candump ${can_device} | \
	while read interface eid plength frame; do

		eid=0x$eid
		FARR=($frame)
		length=${#FARR[*]}
	
		mac_src=$(((eid>>24)&0x1F))
		mac_dst=$(((eid>>19)&0x1F))
		is_first=$(((eid>>18)&1))
		fragment_left=$(((eid>>10)&0xFF))
		packet_serial=$((eid&0x3FF))

		if [ $is_first == 0 ]; then

			HARR=(${FARR[0]} ${FARR[1]} ${FARR[2]} ${FARR[3]})
			hex_id=${FARR[0]}${FARR[1]}${FARR[2]}${FARR[3]}
			id=0x${hex_id}
			priority=$(((id>>30)&3))
			src=$(((id>>25)&0x1F))
			dst=$(((id>>20)&0x1F))
			dport=$(((id>>14)&0x3F))
			sport=$(((id>>8)&0x3F))

			length=0x${FARR[4]}${FARR[5]}
		
			doffset=6
			DARR=()
		else
			doffset=0
		fi

		nbyte=${#FARR[*]}
		for (( i=doffset; i<nbyte; i++ )); do DARR+=(${FARR[i]}); done

		if [ $fragment_left == 0 ]; then
			length=${#DARR[*]}
			echo "$src:$sport $dst:$dport $length ${hex_id} ${DARR[*]}"
		fi
	
	done 

elif $mode_file; then

	if [ "$input_file" == "-" ]; then
		cat
	else
		cat "$input_file" 
	fi | \
	while read full_packet; do
	
		FARR=($full_packet)

		HARR=(${FARR[0]} ${FARR[1]} ${FARR[2]} ${FARR[3]})
		hex_id=${FARR[0]}${FARR[1]}${FARR[2]}${FARR[3]}
		id=0x${hex_id}
		priority=$(((id>>30)&3))
		src=$(((id>>25)&0x1F))
		dst=$(((id>>20)&0x1F))
		dport=$(((id>>14)&0x3F))
		sport=$(((id>>8)&0x3F))

		flen=${#FARR[*]}

		unset	FARR[0]
		unset	FARR[1]
		unset	FARR[2]
		unset	FARR[3]
		[ 4 -le $flen ] && unset FARR[flen-4]
		[ 3 -le $flen ] && unset FARR[flen-3]
		[ 2 -le $flen ] && unset FARR[flen-2]
		[ 1 -le $flen ] && unset FARR[flen-1]

		DARR=(${FARR[*]})
		length=${#FARR[*]}

		echo "$src:$sport $dst:$dport $length ${hex_id} ${DARR[*]}"

	done

fi | \
while read src dst length header data; do

	A=(${src//:/ })
	src=${A[0]}
	sport=${A[1]}

	A=(${dst//:/ })
	dst=${A[0]}
	dport=${A[1]}

	darr=($data)
	dk_cmd=${darr[0]}
	dk_port=0x${darr[1]}
	downlink_flags=$((dk_port ^ GETF_DK_PORT_DEFAULT))

	if [ "$dport" == 12 ] && [ "${darr[0]}" == 00 ] && [ $downlink_flags -le 7 ]; then

		unset	darr[0]
		unset	darr[1]
		darr=(${darr[*]})

		if [ $(( downlink_flags & GETF_PORT_FLAG_SIZE_OFFSET_FILENAME )) -ne 0 ]; then

			has_size_offset_filename=true

			size=`wideenc_decode ${darr[*]}`
			skip=`wideenc_length ${darr[*]}`
			for ((i=0;i<skip;i++)); do unset darr[i]; done
			darr=(${darr[*]})

			offset=`wideenc_decode ${darr[*]}`
			skip=`wideenc_length ${darr[*]}`
			for ((i=0;i<skip;i++)); do unset darr[i]; done
			darr=(${darr[*]})

			f=0
			xxd="0"
			while [ -n "${darr[f]}" ] && [ "${darr[f]}" != "00" ]; do 
				xxd+=" ${darr[f]}"
				unset	darr[f]
				f=$((f+1)) 
			done	
			unset	darr[f]

			filename=`echo $xxd | xxd -r`
			darr=(${darr[*]})
		else
			has_size_offset_filename=false
		fi

		if [ $(( downlink_flags & GETF_PORT_FLAG_INODE_POSITION )) -ne 0 ]; then
			has_inode_position=true

			inode=`wideenc_decode ${darr[*]}`
			skip=`wideenc_length ${darr[*]}`
			for ((i=0;i<skip;i++)); do unset darr[i]; done
			darr=(${darr[*]})

			position=`wideenc_decode ${darr[*]}`
			skip=`wideenc_length ${darr[*]}`
			for ((i=0;i<skip;i++)); do unset darr[i]; done
			darr=(${darr[*]})

		else
			has_inode_position=false
		fi

		if [ $(( downlink_flags & GETF_PORT_FLAG_REED_SOLOMON )) -ne 0 ]; then
			has_reed_solomon=true

			rs_length=`wideenc_decode ${darr[*]}`
			skip=`wideenc_length ${darr[*]}`
			for ((i=0;i<skip;i++)); do unset darr[i]; done
			darr=(${darr[*]})

			rs_key=`wideenc_decode ${darr[*]}`
			skip=`wideenc_length ${darr[*]}`
			for ((i=0;i<skip;i++)); do unset darr[i]; done
			darr=(${darr[*]})
			
		else
			has_reed_solomon=false
		fi


		length=${#darr[*]}

		echo -n "{ "
		if $has_size_offset_filename; then
			echo -n "\"size\": $size, \"offset\": $offset, \"filename\": \"$filename\", "
		fi

		if $has_inode_position; then
			echo -n "\"inode\": $inode, \"position\": $position, "
		fi

		if $has_reed_solomon; then
			echo -n "\"rs_length\": $rs_length, \"rs_key\": $rs_key, "
		fi

		darr_str=${darr[*]}
		echo -n "\"length\": $length, \"fragment\": \"${darr_str// /}\""
		echo " }"
		

	fi
done