#!/bin/bash

[[ $EUID == 0 ]] || exec sudo -E "$BASH_SOURCE" "$@"

set -eE -o pipefail
trap 'echo "$0:$LINENO:error: \"$BASH_COMMAND\" returned $?" >&2' ERR

shopt -s nullglob

ret=0
for d; do
    vol=${d##*/}
    cd /mnt/root/btrbk
    snaps=($vol.20*)
    if [[ ! $snaps ]]; then
        # no snapshots yet
        continue
    fi
    # when a btrbk bugfix makes it into the distro,
    # we might replace this with btrbk list latest /mnt/root/$vol | ...
    # note: this is duplicated in mount-latest-subvol
    last_snap=$(
        for f in ${snaps[@]}; do
            printf "%s %s\n" $(date -d $(sed -r  's/(.{4})(..)(.{5})(..)(.*)/\1-\2-\3:\4:\5/' <<<${f#$vol.}) +%s) $f
        done | sort -r | head -n 1 | awk '{print $2}'
             )
    if [[ ! $last_snap ]]; then
        echo "$d stale"
        ret=1
        continue
    fi
    stale=true
    if btrfs sub show $d|sed '0,/^\t*Snapshot(s):/d;s/^\s*//' | \
            grep -xF btrbk/$last_snap &>/dev/null; then
        stale=false
    else
        last_uuid=$(btrfs sub show $last_snap| awk '$1 == "UUID:" {print $2}')
        if btrfs sub show $d| grep "^\s*Parent UUID:\s*$last_uuid$" &>/dev/null; then
            stale=false
        fi
    fi
    stale_dir=/nocow/btrfs-stale
    stale_file=$stale_dir/$vol
    if $stale; then
        mkdir -p $stale_dir
        printf "%s\n" $last_snap > $stale_file
        echo "$d stale"
        ret=1
        continue
    else
        rm -f $stale_file
    fi
done
exit $ret

# todo: figure out what to do when there are no
# snapshots yet. I guess that should be
# yes to being stale? see the implications
# in the other script.