#!/bin/bash

#####
#
# Scanelf-Packagecheck -- Attempts to find and rebuild broken link-level
#                         dependencies.
#
# Goals: - Don't use tempfiles.
#        - As fast as possible.
#        - Package-manager agnostic.
#
# TODO: Sanity checks.
#
# NOTE: If there's ever a package manager that doesn't respect --pretend, bugs
#       will arise.
#
#####

# Readonly variables:
declare -r APP_NAME="${0##*/}" # The name of this application
declare -r OIFS="$IFS"         # Save the IFS

# Other global variables:
declare -a pm_opts         # Options passed to the package manager
declare -a orphans_to_skip # libs to ignore

. /etc/init.d/functions.sh

##
# Print usage when option is -h, --help, or not understood.
# Usually quit afterwords.
print_usage() {
# TODO: Make this more complete.
cat << EOF
Usage: $APP_NAME [OPTIONS] [--] [PACKAGE_MANAGER_OPTIONS]

Broken reverse dependency rebuilder.

  -d, --debug           Way too much information (uses bash's set -xv)
  -h, --help            Print this usage
  -m, --package-manager Specify a package manager (default is Portage)
  -q, --quiet           Less output
  -p, --pretend         Pass --pretend to package-manager
  -v, --verbose         More output

All options after -- are passed directly to your package manager.

Examples:
 - $APP_NAME -m pkgcore -pv
 - $APP_NAME --quiet -- --ask

Report bugs to <http://bugs.gentoo.org>
EOF
}

##
# Exit and optionally output to sterr.
die() {
	local status=$1
	shift
	[[ $1 ]] && eerror "$@"
	exit $status
}

##
# scan the filesystem for information about binaries.
do_scanelf() {
	# Block "Permission denied" errors with 2> /dev/null
	scanelf -BlpRF'%F %n' 2> /dev/null
}

##
# Get a list of orphaned files
get_orphans() {
	local IFS=$'\n'
	awk '{
		$1 = ""                            # Ignore the binary
		split($2, sonames, ",")            # Split across commas
		for(soname in sonames) {
			soname = sonames[soname]         # Reassign index to value
			if(!seen[soname]++) print soname # Print if unique and not masked
		}
	}' <<< "$scanelf" | grep -Fv "${orphans_to_skip[*]}" | qfile -Cof-
}

##
# Get a list of objects that need orphaned files.
get_needful_objs() {
	local IFS=$'\n'
	grep -F "${orphans[*]}" <<< "$scanelf" | awk '{print $1}'
}

##
# Get a list of packages that own the objects that need orphaned files.
get_needful_pkgs() {
	qfile -qvC "${needful_objs[@]}" | sort -u
}

##
# Format the list of packages as cat-egory/pkg:SLOT
get_rebuild_list() {
	local pkg
	for pkg in "${needful_pkgs[@]}"; do
		qatom "$pkg" | awk '{printf("%s/%s:",$1,$2)}'
		echo $(<"/var/db/pkg/$pkg/SLOT")
	done
}

##
# Verbose output -- only has an effect when --verbose flag is used
chatter() { :; }

##
# Get whole-word commandline options preceded by two dashes.
get_longopts() {
	case $1 in
		          --debug) set -xv;;
		           --help) print_usage
		                   exit 0;;
		--package-manager) if (( $# > 1 )); then
		                     shift
		                     get_pm "$@"
		                   else
		                     get_pm "${1#*=}"
		                   fi;;
		        --pretend) pm_opts+=("--pretend");;
		          --quiet) einfo() { :; }; ewarn() { :; };;
		        --verbose) chatter() { einfo "$@"; };;
		                *) print_usage
		                   die 1 "Encountered unrecognized option $1";;
	esac
}

##
# Get single-letter commandline options preceded with a single dash.
get_shortopts() {
	local OPT OPTSTRING OPTARG OPTIND
	while getopts ":dhm:qpv" OPT; do
		case $OPT in
			d) set -xv;;
			h) print_usage
			   exit 0;;
			m) get_pm "$OPTARG";;
			p) pm_opts+=("-p");;
			q) einfo() { :; }; ewarn() { :; };;
			v) chatter() { einfo "$@"; };;
			*) print_usage
			   die 1 "Encountered unrecognized option $OPTARG";;
		esac
	done
}

##
# Get command-line options.
get_opts() {
	local -a args
	while [[ $1 ]]; do
		case $1 in
			 --) shift; break;;
			 -*) while true; do
			       args+=("$1")
			       shift
			       [[ ${1:--} = -* ]] && break
			     done
			     if [[ ${args[0]} = --* ]]; then
			       get_longopts  "${args[@]}"
			     else
			       get_shortopts "${args[@]}"
			     fi;;
			  *) print_usage
			     die 1 "Unrecognized option $1";;
		esac
		unset args
	done
	pm_opts=( "$@" )

	# Make sure we have superuser rights or --pretend is set
	if (( UID )) && is_real_merge; then
		ewarn "You are not superuser."
		ewarn "Prepending --pretend to package manager options."
		pm_opts=("--pretend" "${pm_opts[@]}")
	fi
	(( ${#pm_opts} )) && chatter "Package manager options set to ${pm_opts[@]}"
}

##
# 
is_real_merge() {
	local IFS=$'\a' # Using BEL as a delimiter is usually safe.
	case $'\a'"${pm_opts[*]}"$'\a' in
		# If one of the elements is -p or --pretend, return false
		*$'\a'--pretend$'\a'*|*$'\a'-p$'\a'*) return 1;;
	esac

	# The merge is not --pretend, return true
	return 0;
}

##
# Package-manager wrapper function.
# Ideally in the future this could be specified by an external config file
# (in a hopefully secure manner).
remerge() {
	ewarn "No package manager specified. Using Portage by default."
	get_pm Portage # Redefines remerge()
	remerge "$@"
}

##
# Redefine the package-manager wrapper function based on commandline options.
# TODO: Get this from a config file.
get_pm() {
	if [[ ! $1 ]]; then
		ewarn "You must specify a package manager"
		return 1
	fi
	chatter "Setting package manager to $1."
	shopt -s nocasematch
	case $1 in
		Pkgcore) if hash pmerge 2> /dev/null; then
		           remerge() {  pmerge -1D "$@"; }
		         else
		           eerror "Unable to find pmerge binary in PATH."
		           eerror "Please make sure it's properly installed."
		           ewarn  "Falling back to Portage default."
		           get_pm Portage
		         fi;;
		Paludis) if hash Paludis 2> /dev/null; then
		           remerge() { paludis -1i "$@"; }
		         else
		           eerror "Unable to find Paludis binary in PATH."
		           eerror "Please make sure it's properly installed."
		           ewarn  "Falling back to Portage default."
		           get_pm Portage
		         fi;;
		Portage) if hash emerge 2> /dev/null; then
		           remerge() { emerge -1D "$@"; }
		         else
		           eerror "Unable to find emerge binary in PATH."
		           eerror "Please make sure Portage is properly installed"
		           eerror "or specify an alternative package manager."
		           die 1  "Unable to continue without a package manager."
		         fi;;
		      *) eerror "Unknown package manager $1:"
		         eerror 'Valid values are "Portage", "Pkgcore", and "Paludis".'
		         ewarn  "Using Portage by default."
		         get_pm Portage;;
	esac
	shopt -u nocasematch
}

get_env() {
	[[ -d /etc/revdep-rebuild ]] || return 0
	local conf
	for conf in /etc/revdep-rebuild/*; do
		[[ -r $conf ]]&& orphans_to_skip+=($(. "$conf"; echo "$LD_LIBRARY_MASK"))
	done
}

##
# Usage: countdown n
#        n: number of seconds to count
countdown() {
	local i
	for ((i=1; i<$1; i++)); do
		echo -ne '\a.'
		((i<$1)) && sleep 1
	done
	echo -e '\a.'
}

do_remerge() {
	einfo 'All prepared. Starting rebuild'
	is_real_merge && countdown 10

	# Link file descriptor #6 with stdin so --ask will work
	exec 6<&0

	remerge "${pm_opts[@]}" "${unsorted_pkgs[@]}" <&6

	# Now restore stdin from fd #6, where it had been saved, and close fd #6
	# ( 6<&- ) to free it for other processes to use.
	exec 0<&6 6<&-
}

main() {
	get_opts "$@"

	# HACK: Don't depend on r-r config files in the future.
	einfo "Grabbing masks from /etc/revdep-rebuild"
	get_env

	echo
	
	einfo "Generating list of binaries"
	einfo "(This takes a while the first time, but subsequent runs are faster.)"
	local scanelf=$(do_scanelf)

	echo
	
	einfo "Generating list of orphans"
	local orphans=($(get_orphans))
	(( ${#orphans[@]} )) || die 0 "No orphaned files found -- nothing to fix"
	ewarn "The following files are orphans: ${orphans[@]}"

	echo
	
	einfo "Generating list of binaries linking to those orphans"
	local needful_objs=($(get_needful_objs))
	(( ${#needful_objs[@]} )) ||
		die 1 "No objects appear to need those files. This may indicate a bug."
	ewarn "The following files link to those orphans: ${needful_objs[@]}"

	echo
	
	einfo "Generating list of packages to rebuild"
	local needful_pkgs=($(get_needful_pkgs))
	local unsorted_pkgs=($(get_rebuild_list))
	ewarn "The following packages need to be rebuilt: ${unsorted_pkgs[@]}"

	echo
	
	do_remerge
}
main "$@"