#! /bin/bash

shopt -s dotglob

prog=$(basename $0)

usage()
{
    rv=$1
    cat >&2 <<-EOF
	usage: $prog [--jre-headless] [--jre] [--plugin] [ -t|--test|-v|--verbose]
	           -l|--list [<jname>]
	           -s|--set <jname>
	           -a|--auto
	           -h|-?|--help
	EOF
    exit $rv
}

action=
uaopts='--quiet'

while [ "$#" -gt 0 ]; do
    case "$1" in
      -a|--auto)
	[ -z "$action" ] || usage 1
	action=auto;;
      -hl|--jre-headless)
	hlonly=yes;;
      -j|--jre)
	jreonly=yes;;
      --plugin)
	pluginonly=yes;;
      -l|--list)
	[ -z "$action" ] || usage 1
	action=list
	if [ "$#" -gt 0 ]; then
	    shift
	    jname=$1
	fi
	;;
      -s|--set)
	[ -z "$action" ] || usage 1
	action=set
	shift
	[ "$#" -gt 0 ] || usage 1
	jname=$1
	;;
      -t|--test)
	dryrun=yes
	uaopts="$uaopts --test";;
      -v|--verbose)
	verbose=yes
	uaopts="${uaopts/--quiet/}";;
      -h|-?|--help)
	usage 0;;
      -*)
	echo "X: $1"
	usage 1;;
      *)
	break;;
    esac
    shift
done

[ "$#" -eq 0 ] || usage 1
[ -n "$action" ] || usage 1

which='^(hl|jre|jdk|plugin|DUMMY) '
if [ -n "$hlonly$jreonly$pluginonly" ]; then
    which='^('
    [ -n "$hlonly" ] && which="${which}hl|"
    [ -n "$jreonly" ] && [ -n "$hlonly" ] && which="${which}jre|"
    [ -n "$jreonly" ] && [ -z "$hlonly" ] && which="${which}hl|jre|"
    [ -n "$pluginonly" ] && which="${which}plugin|"
    which="${which}DUMMY) "
fi

top=/usr/lib/jvm

if [ -n "$jname" ]; then
    arch=$(dpkg --print-architecture)
    if [ ! -x $top/$jname/bin/java ] && [ -x $top/$jname-$arch/bin/java ]; then
	echo >&2 "$prog: obsolete <jname>, please use $jname-$arch instead"
	jname=$jname-$arch
    fi
    case "$jname" in
	/*) jdir=$jname; jname=$(basename $jdir);;
	*)  jdir=$top/$jname
    esac
    if [ ! -d $jdir ]; then
	echo >&2 "$prog: directory does not exist: $jdir"
	exit 1
    fi
    if [ -f $top/.$jname.jinfo ]; then
	jinfo=$top/.$jname.jinfo
    elif [ -f $top/$jname.jinfo ]; then
	jinfo=$top/$jname.jinfo
    else
	echo >&2 "$prog: file does not exist: $top/.$jname.jinfo"
	exit 1
    fi
fi

vecho()
{
    [ -z "$verbose" ]  || echo >&2 "$@"
}

jinfo_files=

do_auto()
{
    vecho "resetting java alternatives"
    awk "/$which/ {print \$2}" $top/*.jinfo | sort -u \
	| \
    while read name; do
	update-alternatives $uaopts --auto $name
    done
}

do_list()
{
    vecho "listing java alternatives:"
    for i in ${jinfo:-$top/*.jinfo}; do
	alias=$(basename ${i%.jinfo})
	alias=${alias#.}
	prio=$(awk -F= '/priority=/ {print $2}' $i)
	echo $alias $prio $top/$alias
	[ -n "$verbose" ] && egrep "$which" $i
    done
}

do_set()
{
    do_auto

    awk "/$which/ {print}" $jinfo | sort -u \
	| \
    while read type name location; do
	if [ $type = jdk -a -z "$hlonly$jreonly$pluginonly" -a ! -f $location ]; then
	    echo >&2 "$prog: jdk alternative does not exist: $location"
	    continue
	fi
	if [ $type = plugin -a -z "$hlonly$jreonly" -a ! -f $location ]; then
	    echo >&2 "$prog: plugin alternative does not exist: $location"
	    continue
	fi
	update-alternatives $uaopts --set $name $location
    done
}

if [ "$action" != list ] && [ "$(id -u)" -ne 0 ]; then
    echo >&2 "$prog: no root privileges"
    exit 1
fi

do_$action