#!/bin/sh -e

init () {
    [ -n "$1" ] || printArgs
    mkdir -p "$(dirname $1)"
    [ -f "$1" ] || cat >"$1" </dev/null
}

get () {
    [ -n "$2" ] || printArgs
    grep "^$2"$'\t' "$1" | cut -f3-
}

show () {
    cut -f1,3- "$1"
}

filter () {
    tbl="$1"
    shift 1
    cut -f1,2  "$tbl" \
	| while read key version; do
	    echo -e "$key\t$(($version+$RANDOM))"
        done > "$tbl".ver
    cut -f1,3- "$tbl" \
	| "$@" \
	| join -t$'\t' "$tbl".ver  - \
	> "$tbl"~
    mv "$tbl"~ "$tbl"
    rm "$tbl".ver
}

update () {
    [ -n "$2" -a -n "$3" ] || printArgs
    oldversion=$(grep "^$2"$'\t' "$1" | cut -f2)
    tmpfile="$1.update"
    echo -e "$2\t$(($oldversion + 1 + $RANDOM))\t$3" > "$tmpfile"
    merge "$1" "$tmpfile"
    if [ -n "$4" ]; then
	# broadcast update
	gzip <"$tmpfile" >"$tmpfile.gz"
	hbbpc $4 p2ptbl/$(basename "$1") - <"$tmpfile.gz"
	rm "$tmpfile.gz"
    fi
    rm "$tmpfile"
}

merge () {
    # we use sort instead of merge here to be robust in case the rows
    # are not sorted
    sort "$1" "$2" \
	| {
	oldkey=""
	oldversion=0
	oldval=""
	while read key version val; do
	    if [ "$key" == "$oldkey" ]; then
		if [ "$version" -gt "$oldversion" ]; then
		    oldversion="$version"
		    oldval="$val"
		fi
	    else
		[ -n "$oldkey" ] && echo -e "$oldkey\t$oldversion\t$oldval"
		oldkey="$key"
		oldversion="$version"
		oldval="$val"
	    fi
	done
	[ -n "$oldkey" ] && echo -e "$oldkey\t$oldversion\t$oldval"
    } > "$1~"
    mv "$1~" "$1"
}

gossip() {
    tgts="$2"
    if="$3"
    [ "$tgts" -gt 0 -a -n "$if" ] 2>/dev/null || printArgs

    # binary search over number of sent lines until size is maximized
    # and below target size
    lc=$(wc -l <"$1")
    [ $lc == 0 ] && return
    shuf -v seed=$RANDOM <"$1" >"$1.gossip"
    while [ $lc -ge 1 ]; do
	head -n$lc "$1.gossip" | gzip >"$1.gossip.gz"
	if [ $tgts -ge $(wc -c <"$1.gossip.gz") ]; then
	    hbbpc $if p2ptbl/$(basename "$1") - <"$1.gossip.gz"
	    rm "$1.gossip" "$1.gossip.gz"
	    return;
	fi
	lc=$(($lc / 2))
    done
    rm "$1.gossip" "$1.gossip.gz"
    echo "$1 has rows bigger then requested packet size"
    exit 1
}

printArgs () {
    echo -e >&2 "Usage:
$0 init   table
$0 get    table key
$0 show   table
$0 update table key value [interface]
$0 filter table program [args]
$0 merge  table foreign-table
$0 gossip table target-size interface"
    exit 1
}

checkTable () {
    [ -n "$1" ] || printArgs;
    [ -f "$1" ] || { 
	echo >&2 "$1 is no P2P table"; 
	printArgs;
    }
}

lockTable () {
    checkTable "$2"
    exec 666<"$2"
    flock "$1" 666
}

case "$1" in
    init) 
	init "$2"
	;;
    get)
	lockTable -s "$2"
	get "$2" "$3"
	;;
    show)
	lockTable -s "$2"
	show "$2"
	;;
    filter)
	tbl="$2"
	shift 2
	lockTable -x "$tbl"
	filter "$tbl" "$@"
	;;
    update)
	lockTable -s "$2"
	update "$2" "$3" "$4" "$5"
	;;
    merge)
	lockTable -x "$2"
	checkTable "$3" 
	merge "$2" "$3"
	;;
    gossip)
	lockTable -s "$2"
	gossip "$2" "$3" "$4"
	;;
    *) 
	printArgs
	;;
esac