#! /bin/sh

set -e
case $# in
  0 | 1 | 2 | 3)
    echo >&2 "Usage: $0 HOST PATH ARCH:ARCH:... DIST..."
    exit 1
    ;;
  *)
    RSYNC_HOST=$1 RSYNC_PATH=$2 WANT_ARCH=$3; shift 3
    ;;
esac

## Check the available distributions for architectures.
: ${RSYNC="rsync"}
for dist in "$@"; do
  $RSYNC --list-only $RSYNC_HOST::$RSYNC_PATH/dists/$dist/main/
done | {

  ## Gather up excluded architectures as we go.
  excludes=""

  while read mode size date time name; do

    ## Check directories of binary packages.  If it's an architecture we
    ## don't want to reject, then continue on.
    case "$name" in
      binary-all)
	continue
	;;
      binary-*)
	arch=${name#binary-}
	case ":$WANT_ARCH:" in *:"$arch":*) continue ;; esac
	;;
      *)
	continue
	;;
    esac

    ## Pick out the architecture name.  Check whether we've seen it before.
    arch=${name#binary-}
    case " $excludes " in
      *" $arch "*)
	;;
      *)
	excludes="${excludes+$excludes }$arch"
	;;
    esac
  done

  ## Done.  Print out the finished list.
  echo $excludes
}