#!/bin/bash

##################################################################
# Copyright (C) 2005 DEMAINE Benoit-Pierre (benoit@demaine.info)
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
##################################################################

###BEGIN
# This script is written for those stupid people like me
# who like launching several emerge at the same time
# It tries to determine whether launching a new emerge at once is risky or not.

# It can take one or two arguments.
# Each argument can be composite; composite arguments are delimited with "

# if you give two arguments, it says whether the two emerge can be done in parallel:
# $ emerge-diff xmms wireless-tools
# usually returns OK, because their dependencies do not overlap.
# $ emerge-diff xmms xmms
# will always fails since dependencies of xmmms overlap with himself.
# $ emerge-diff "xmms wireless-tools" "enlightenment mplayer"
# will tell if it is possible to do side by side:
# $ emerge xmms wireless-tools
# $ emerge enlightenment mplayer

# If the script reports any risk, it will print the list of
# common dependencies between the first and the second argument.
# If you first emerge the list returned, then you can emerge side
# by side the first and second argument without breaking any thing.

# if you provide only one argument, the script will list
# the running emerges, and build the dependency list of all packages being emerged.
# this allows to determine whether you can start a 2nd (or 3rd) emerge
# without stopping the ones already running to add arguments.
#
# If you supply only one agument, the script WILL NOT analyse whether
# already running emerges may break portage !!!

# emerge-diff
# without any argument will list packages being emerged.
###END

# I am sorry I did not find any way to print out the list of deps
# a way that you can emerge it at once :(

EMERGE="/usr/bin/emerge -p "
E="emerge"
GREP="/bin/grep"
G="grep"
CUT="/bin/cut"
COMM="/bin/comm -1 -2"
ECHO="/bin/echo"
SORT="/bin/sort"
PS="/bin/ps"
SED="/bin/sed"
S="sed"
TR="/bin/tr"
CAT="/bin/cat"
HEAD="/bin/head"
TAIL="/usr/bin/tail"

# Prefix of temp files ...
TMP="/tmp/ziouplop"

# is there an argument ?
if [ -z "$1" ]
then
	Z=" "
else
	Z="$1"
fi

if [ "$1" = "-h" -o  "$1" = "--help" ]
then
	begin=`$CAT $0 | $GREP -n '###BEGIN' | $TR '\n' ' ' | $CUT -d ":" -f 1 | $CUT -d " " -f1`
	end=`$CAT $0 | $GREP -n '###END' | $TR '\n' ' ' | $CUT -d ":" -f 1 | $CUT -d " " -f1`

	# compute length
	length=$(($end-$begin-1))
	
	$CAT $0 | $HEAD -n $(($end-1)) | $TAIL -n $length
	
	exit 0
fi

if [ -z "$2" ]
then
	R=`eval "${PS} ax | ${GREP} $E | ${GREP} -v $G | ${GREP} -v $S | ${GREP} -v "$0" | $SED 's/\([^.]*\)emerge\([^.]*\)$/\2/g' | $SED 's/ -[^ ]*\ //g' | $TR '\n' ' '"`
	if [ -z "$R" ]
	then
		$ECHO "No emerge running: please give two arguments."
		exit 1
	fi
	$ECHO "Actually emerging $R"
else
	R="$2"
fi

SKIP=" ${GREP} -v \"These are the packages\" | ${GREP} -v \"Calculating dependencies\" | ${GREP} -v \"Total size of downloads\" | ${CUT} -d \"]\" -f2 | ${CUT} -d \" \" -f2 | ${GREP} \"/\" | ${SORT}"

eval "${EMERGE} "$Z" | ${SKIP}" >${TMP}1
eval "${EMERGE} "$R" | ${SKIP}" >${TMP}2

R=`eval "${COMM} ${TMP}1 ${TMP}2"`

if [ -z "$R" ]
then
	$ECHO "No overlapping detected."
	exit 0
else
	$ECHO "OVERLAPING DETECTED - try continue at your own risks."
	$ECHO "$R"
	exit 1
fi