#!/bin/bash

# Back up one filesystem via backshift

export PATH=$PATH:/usr/local/bin

# Intentionally not using set -e, because we don't want find to cause the whole schmear to error out
set -eu

# With pipefail in effect, a single bad file seen by find(1) can cause the whole command to file. We don't want that.
# set -o pipefail

function usage
{
    retval="$1"
    case "$retval" in
        0)
            ;;
        1)
            exec 1>&2
            ;;
        *)
            echo "$0: usage recevied invalid retval" 1>&2
            exit 1
            ;;
    esac
    echo "Usage: $0 --filesystem /fs --save-directory /save/dir"
    echo
    echo Note that the behaviour varies slight from on/off a tty.
    echo On a tty, progress is moderate.
    echo Off a tty, progress is none.
    echo
    exit "$retval"
}

filesystem=""
save_directory=""

while [ "$#" -ge 1 ]
do
    case "$1" in
        -h|--help)
            usage 0
            ;;
        --filesystem)
            filesystem="$2"
            shift
            ;;
        --save-directory)
            save_directory="$2"
            shift
            ;;
        *)
            echo "$0: Unrecognized option: $1" 1>&2
            usage 1
            ;;
    esac
    shift
done

case "$filesystem" in
    "")
        echo "$0: --filesystem is a required argument" 1>&2
        usage 1
        ;;
    /*) ;;
    *)
        echo "$0: --filesystem argument must start with a /" 1>&2
        usage 1
        ;;
esac

case "$filesystem" in
    /) subset=just-slash ;;
    *) subset=$(echo "$filesystem" | sed -e 's#^/#just-#' -e 's#/#-#g') ;;
esac

case "$save_directory" in
    "")
        echo "$0: --save-directory is a required argument" 1>&2
        usage 1
        ;;
    /*) ;;
    *)
        echo "$0: --save-directory must specify an absolute path" 1>&2
        usage 1
        ;;
esac

if tty -s
then
    progress=moderate
else
    progress=none
fi

# We assume that swapfiles, if any, are under a directory called /swapfile
find "$filesystem" -xdev -wholename /swapfile -prune -o -print0 | \
    just-one \
        --command "backshift --save-directory \"$save_directory\" --subset $subset --backup --progress-report $progress" \
        --string "backshift-$subset" 2>&1