#!/bin/sh
   # update-alternatives
   #
   # Copyright (C) 2001 Carl D. Worth
   #
   # This program was inspired by the Debian update-alternatives program
   # which is Copyright (C) 1995 Ian Jackson. This version of
   # update-alternatives is command-line compatible with Debian's for a
   # subset of the options, (only --install, --remove, and --help)
  #
  # 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, 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.
  
  set -e
  
  # admin dir
  ad="$OPKG_OFFLINE_ROOT@opkglibdir@/opkg/alternatives"
  
  usage() {
          echo "update-alternatives: $*
  
  Usage: update-alternatives --install <link> <name> <path> <priority>
         update-alternatives --remove <name> <path>
         update-alternatives --help
  <link> is the link pointing to the provided path (ie. /usr/bin/foo).
  <name> is the name in $ad/alternatives (ie. foo)
  <path> is the name referred to (ie. /usr/bin/foo-extra-spiffy)
  <priority> is an integer; options with higher numbers are chosen.
  " >&2
          exit 2
  }
  
  quit() {
          echo "update-alternatives: $*" >&2
          exit 2
  }
  
  register_alt() {
          [ $# -lt 2 ] && return 1
          local name="$1"
          local link="$2"
  
          if [ ! -d $ad ]; then
                  mkdir -p $ad
          fi
  
          if [ -e "$ad/$name" ]; then
                  local olink=`head -n 1 $ad/$name`
                  if [ "$link" != "$olink" ]; then
                          echo "update-alternatives: Error: cannot register alternative $name to $link since it is already registered to $olink" >&2
                          return 1
                  fi
          else
                  echo "$link" > "$ad/$name"
          fi
  
          return 0
  }
  
  protect_slashes() {
          sed -e 's/\//\\\//g'
  }
  
  remove_alt() {
          [ $# -lt 2 ] && return 1
          local name="$1"
          local path="$2"
          
          [ ! -f $ad/$name ] && return 0
  
          path=`echo $path | protect_slashes`
          sed -ne "/^$path\>.*/!p" $ad/$name > $ad/$name.new
          mv $ad/$name.new $ad/$name
  }
  
  add_alt() {
          [ $# -lt 3 ] && return 1
          local name="$1"
          local path="$2"
          local priority="$3"
          remove_alt $name $path
          echo "$path $priority" >> $ad/$name
  }
  
  find_best_alt() {
          [ $# -lt 1 ] && return 1
          [ ! -f $ad/$name ] && return 0
  
          link=$OPKG_OFFLINE_ROOT/`head -n 1 $ad/$name`
  
          prio=`sed -ne "1!p" $ad/$name | sed -e "s/\(.*\) \(.*\)/\2 \1/g" | sort -nr | head -n 1 | sed 's/ [^ ]*$//'`
          if [ -z "$prio" ]; then
                 echo "update-alternatives: removing $link as no more alternatives exist for it"
                 rm $ad/$name
                 if [ -L $link ]; then
                         rm $link
                 fi
                 return 0
         fi
 
         ## Find last line with highest priority.
         path=`grep "${prio}$" $ad/$name | tail -n 1 | sed 's/ [^ ]*$//'`
 
         if [ ! -e $link -o -L $link ]; then
                 local link_dir=`dirname $link`
                 if [ ! -d $link_dir ]; then
                         mkdir -p $link_dir
                 fi
                 if [ -h $link -a -d $link ]; then
                         # If $link exists and the target is a directory,
                         # 'ln -sf $path $link' doesn't replace the link to
                         # that directory, it creates new link inside.
                         echo "update-alternatives: Removing $link".
                         rm -f $link
                 fi
                 ln -sf $path $link
                 echo "update-alternatives: Linking $link to $path"
         else
                 echo "update-alternatives: Error: not linking $link to $path since $link exists and is not a link"
                 return 1
         fi
 
         return 0
 }
 
 do_install() {
         if [ $# -lt 4 ]; then
                 usage "--install needs <link> <name> <path> <priority>"
         fi
         local link="$1"
         local name="$2"
         local path="$3"
         local priority="$4"
 
         path=`echo $path | sed 's|/\+|/|g'`
 
         # This is a bad hack, but I haven't thought of a cleaner solution yet...
         [ -n "$OPKG_OFFLINE_ROOT" ] && path=`echo $path | sed "s|^$OPKG_OFFLINE_ROOT/*|/|"`
 
         register_alt $name $link
         add_alt $name $path $priority
         find_best_alt $name
 }
 
 do_remove() {
        if [ $# -lt 2 ]; then
                 usage "--remove needs <name> <path>"
         fi      
         local name="$1"
         local path="$2"
 
         path=`echo $path | sed 's|/\+|/|g'`
 
         # This is a bad hack, but I haven't thought of a cleaner solution yet...
         [ -n "$OPKG_OFFLINE_ROOT" ] && path=`echo $path | sed "s|^$OPKG_OFFLINE_ROOT/*|/|"`
 
         remove_alt $name $path
         find_best_alt $name
 }
 
 ###
 # update-alternatives "main"
 ###
 
 while [ $# -gt 0 ]; do
         arg="$1"
         shift
 
         case $arg in
         --help)
                 usage "help:"
                 exit 0
                 ;;
         --install)
                 do_install $*
                 exit $?
                 ;;
         --remove)
                 do_remove $*
                 exit $?
                 ;;
         *)
                 usage "unknown argument \`$arg'"
                 ;;
         esac
 done
 
 usage "at least one of --install or --remove must appear"
 
 exit 0

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