#! /bin/sh
# Compare multiple kernel versions

# Return more recent of two kernel versions.
if [ $# -eq 0 ]; then
    echo Usage: $0 kernelversion kernelversion ... >&2
    echo Returns greatest of the versions. >&2
    exit 1
fi

unknown()
{
    # Does a -dj kernel come before a -ac kernel?  Or a Linus kernel?
    # Undefined.
    echo Can\'t compare extension \'"$1"\'. >&2
    exit 1
}

firstpart()
{
    echo $1 | sed 's/[-.].*//'
}

lastpart()
{
    echo $1 | sed 's/.*[-.]//'
}

trimlastpart()
{
    echo $1 | sed 's/[-.][^-.]*$//'
}

trimfirstpart()
{
    echo $1 | sed 's/^[^-.]*[-.]//'
}

letters()
{
    echo $1 | tr -d '[0-9]'
}

numbers()
{
    echo $1 | tr -dc '[0-9]'
}

if [ $# -eq 1 ]; then
    echo "$1"
    exit 0
fi

if [ $# -gt 2 ]; then
    FIRST=$1
    shift
    set -- $FIRST $($0 "$@")
fi

VER1=$1
VER2=$2

# Vanity kernels (at end): handle 2.6.3-mm2 vs 2.6.3-rc1-mm3 by comparing
# base first.
TAIL1=$(lastpart $VER1)
TAIL2=$(lastpart $VER2)
if [ x"$(letters $TAIL1)" = x"$(letters $TAIL2)" ]; then
    case "$TAIL1" in
    bk*|rc*|pre*) : ;;
    *)
	BASE1=$(trimlastpart $VER1)
	BASE2=$(trimlastpart $VER2)
	if [ x"$BASE1" = x"$BASE2" ]; then
	    if [ $(numbers $TAIL1) -gt $(numbers $TAIL2) ]; then
		echo $1
	    else
		echo $2
	    fi
	else
	    if [ x$(lkvercmp $BASE1 $BASE2) = x$BASE1 ]; then
		echo $1
	    else
		echo $2
	    fi
	fi
	exit
	;;
   esac
fi

while true; do
    PART1=$(firstpart $VER1)
    PART2=$(firstpart $VER2)
    VER1=$(trimfirstpart $VER1)
    VER2=$(trimfirstpart $VER2)

    PART1LETTERS=$(letters $PART1)
    PART2LETTERS=$(letters $PART2)
    PART1NUMBERS=$(numbers $PART1)
    PART2NUMBERS=$(numbers $PART2)

    if [ "$PART1LETTERS" = "$PART2LETTERS" ]; then
	if [ "$PART1NUMBERS" = "$PART2NUMBERS" ]; then
	    continue;
	else
	    if [ "$PART1NUMBERS" -gt "$PART2NUMBERS" ]; then
		echo $1; exit
	    else
		echo $2; exit
	    fi
        fi
    fi

    case x"$PART1LETTERS" in
    xbk)
        # bk snapshots come after (ie. 2.6.1-bk1 is > 2.6.1).
	# So this always wins.
	case x"$PART2LETTERS" in
	x|xrc|xpre) echo $1; exit;;
	esac
	unknown $PART2LETTERS;;
    x)
	# Final beats everything except bk.
	case x"$PART2LETTERS" in
	xbk) echo $2; exit;;
	xrc|xpre) echo $1; exit;;
	esac
	unknown $PART2LETTERS;;
    xrc)
	# Only a final or bk can win.
	case x"$PART2LETTERS" in
        x|xbk) echo $2; exit;;
	xpre) echo $1; exit;;
        esac
	unknown $PART2LETTERS;;
    xpre)
        # Final, bk or rc can win.
	case x"$PART2LETTERS" in
        x|xbk|xrc) echo $2; exit;;
	xpre) echo $1; exit;;
        esac
	unknown $PART2LETTERS;;
    *)
	unknown $PART1LETTERS;;
    esac
done