#!/bin/dash

# dwhy by www.ramoncasares.com 2011
# License: GPL
# Version: 0.1 (20110323)

dwhy () {
if test "[$1]" = "[]" ; then
   echo "Enter: dwhy filename"
   echo "       to let Debian explain why filename is in your system"
   exit 1
fi

if test -e "$1" ; then
   TARGET="$(readlink -f "$1")"
   if test -L "$1" ; then
      echo "$1 -> $TARGET"
   fi
else
   FIRSTTARGET="$(which "$1")"
   TARGET="$(readlink -f "$FIRSTTARGET")"
   if test -L "$FIRSTTARGET" ; then
      echo "$1 -> $FIRSTTARGET -> $TARGET"
   else
      if test "[$TARGET]" != "[]" ; then
         echo "$1 -> $TARGET"
      fi
   fi
fi

if test "[$TARGET]" = "[]" ; then
   if test "[$(apt-cache -n search "^$1$")]" = "[]" ; then
      echo "$1: file not found, and it is not a package."
      exit 2
   else
      echo "$1: file not found, try as package"
      PACKAGES=$1
   fi
else
   file "$TARGET"
fi

if test "[$PACKAGES]" = "[]" ; then
   PACKAGES=$(dpkg-query --search "$TARGET" | cut -d: -f1 | sed s/,//g)
fi

if test "[$PACKAGES]" = "[]" ; then
   echo "$TARGET is not in a Debian package"
else
 for PACKAGE in $PACKAGES ; do
   DFILE=$(apt-cache show "$PACKAGE" | grep "^Filename: " | cut -d' ' -f2)
   PRIORITY=$(dpkg-query -W -f='${Priority}' $PACKAGE)
   echo "Package: $DFILE [$PRIORITY]"
   dtree $PACKAGE
 done
fi

exit 0
}

dtasks () {
   if test "[$ITASKS]" = "[]" ; then
      ITASKS=$(tasksel --list-tasks | grep "^i" | sed 's/^i \([^\t]*\).*/\1/')
   fi
   TASKS=""
   for TASK in $ITASKS
   do
      if test "$(aptitude search "$1~t$TASK")" != "" ; then
         TASKS="$TASKS $TASK"
      fi
   done
}

dtree () {
if test $# = 0 ; then
   echo "Enter: dtree package1 package2 ..."
   echo "       to draw the tree of packages and tasks of package1 ..."
   return 1
fi

for PACKAGE in $@ ; do
   PRIORITY=$(dpkg-query -W -f='${Priority}' $PACKAGE)
   SEARCH="$(aptitude search "^$PACKAGE$")"
   if test "[$(echo "$SEARCH" | cut -c1)]" = "[i]"
   then
      if test "[$(echo "$SEARCH" | cut -c3)]" = "[A]" ; then
         STATUS="A"
      else
         STATUS="M"
      fi
   else
       STATUS="X"
   fi
   echo -n " $PACKAGE ($STATUS)"
   if test "$PRIORITY" = required -o "$PRIORITY" = important ; then
      echo " <- base system (D)"
   else
      if test "$PRIORITY" = standard ; then
         echo " <- standard system (D)"
      else
         if test "$STATUS" = "M" ; then
            dtasks "$PACKAGE"
            if test "[$TASKS]" != "[]" ; then
               echo -n " <-"
               echo "$TASKS (T)"
            else
               echo ""
            fi
         else
            RPKGS=$(apt-get -qq -s remove "$PACKAGE" \
                    | grep "^Remv" | cut -d' ' -f2 \
                    | grep -vx "$PACKAGE")
            if test $(echo "$RPKGS" | wc -w) -eq 0 ; then
               echo ""
            elif test $(echo "$RPKGS" | wc -w) -eq 1 ; then
               echo -n " <-"
               dtree $RPKGS
            else
               echo -n " <- "
               echo "$RPKGS" | tr "\n" " "
               echo ""
               dtree $(echo $RPKGS | tr "\n" " ")
            fi
         fi
      fi
   fi
done

return 0
}

dwhy $@