#!/bin/bash

if [ -z "${CANPLAYER}" ]; then
	CANPLAYER="canplayer"
fi

die() {
	echo "$*" > /dev/stderr
	exit 1
}

usage() {
	echo "canplayer-bisect <start|stop|clean|good|yes|bad|no|again|where|undo> <logfile> <canplayer options>"
}

is_ready() {
	if [ ! -d .canplayer-bisect ]; then
		usage
		exit 1
	fi

	return 0
}

setup() {
	is_ready

	LOGFILE=$(cat .canplayer-bisect/logfile |head -n 1)

	SAVED_LEN="$(cat .canplayer-bisect/len|tail -n 1)"
	LEN="$(wc -l ${LOGFILE} | awk '{ print $1 }')"

	if [ "$LEN" != "$SAVED_LEN" ]; then
		die "logfile has changed size. restart"
	fi

	CANPLAYER_ARGS=$(cat .canplayer-bisect/args |head -n 1)

	HEAD="$(cat .canplayer-bisect/head |tail -n 1)"
	TAIL="$(cat .canplayer-bisect/tail |tail -n 1)"
}

back() {
	HEAD="$(cat .canplayer-bisect/head |tail -n 2 |head -n1)"
	TAIL="$(cat .canplayer-bisect/tail |tail -n 2 |head -n1)"
}

do_undo() {
	sed -i '$ d' .canplayer-bisect/head
	sed -i '$ d' .canplayer-bisect/tail
}

teardown() {
	mkdir -p .canplayer-bisect
	echo $LEN > .canplayer-bisect/len
	echo $LOGFILE > .canplayer-bisect/logfile
	echo $CANPLAYER_ARGS > .canplayer-bisect/args

	echo $HEAD >> .canplayer-bisect/head
	echo $TAIL >> .canplayer-bisect/tail
}

show() {
	cat $LOGFILE | sed -n ${HEAD},${TAIL}p
}

play() {
	#we *could* pipe directly to canplayer, but then the user can't add -l i to CANPLAYER_ARGS to hunt for packets using looped playback
	the_show="$(mktemp)"
	trap "rm -rf \"${the_show}\"" EXIT

	show > "${the_show}"
	"${CANPLAYER}" ${CANPLAYER_ARGS} -I "${the_show}"
}

do_show() {
	setup

	show
}

check_heads_n_tails() {
	if [ $HEAD -eq $TAIL ]; then
		do_stop
	fi
}

do_good() {
	setup

	check_heads_n_tails

	if [ $(( $HEAD + 1 )) -eq $TAIL ]; then
		TAIL=$HEAD
	else
		TAIL=$(( ( $TAIL - $HEAD ) / 2 + $HEAD - 1 ))
	fi

	teardown
	play
}

do_bad() {
	setup

	check_heads_n_tails

	back
	if [ $(( $HEAD + 1 )) -eq $TAIL ]; then
		HEAD=$TAIL
	else
		HEAD=$(( ( $TAIL - $HEAD ) / 2 + $HEAD ))
	fi

	teardown
	play
}

do_again() {
	setup
	play
}

do_start() {
	do_clean

	LEN="$(wc -l ${LOGFILE} | awk '{ print $1 }')"

	HEAD=1
	TAIL=$LEN

	echo "assuming logfile contains the packets you seek... bisecting to first half"

	teardown
	play
}

do_where() {
	setup
	echo "between $HEAD and $TAIL (+$(( $TAIL - $HEAD ))) of $LOGFILE"
}

do_stop() {
	setup

	if [ "$COMMAND" == "no" ]; then
		echo "failed to find what you were looking for"
		exit 1
	else
		echo "the packets you seek are:"
		do_where
		exit 0
	fi
}

do_clean() {
	rm -rf .canplayer-bisect
}

if [ -z "$1" ]; then
	usage
	exit 1
fi
COMMAND=$1

if [ ! -d .canplayer-bisect ] && [ ! -z "$2" ] && [ ! -e "$2" ]; then
	usage
	exit 1
fi
LOGFILE="$2"

shift
shift
CANPLAYER_ARGS="$*"

case "$COMMAND" in
	start)
		do_start
	;;
	stop)
		do_stop
	;;
	clean)
		do_clean
	;;
	good|yes)
		do_good
	;;
	bad|no)
		do_bad
	;;
	again)
		do_again
	;;
	where)
		do_where
	;;
	undo)
		do_undo
	;;
	show)
		do_show
	;;
esac