#!/bin/bash
#
# Purpose : Back up your home folder with borg to your Nextcloud files, in
#           /mnt/<domain>/.backup-<hostname>. Run daily by
#           coredesktop-backup.timer; `configure backup` sets it up.
#
# Keeps 7 daily, 4 weekly and 6 monthly backups. To leave out more, list
# paths or borg patterns in ~/.config/coredesktop/backup-exclude, one per line.

# Wrapped in { ...; exit; } so bash reads the whole script up front; update
# replaces this file (git pull) while a backup may be running.
{

BACKUP_CONF="$HOME/.config/coredesktop/backup.conf"
USER_EXCLUDE="$HOME/.config/coredesktop/backup-exclude"

# Tell the desktop when a backup fails, as no one watches the timer
fail() {
  echo "$1" >&2
  notify-send --app-name=CoreDesktop --icon=dialog-error "Backup failed" "$1" 2> /dev/null
  exit 1
}

[ -f "$BACKUP_CONF" ] || fail "Backups aren't set up. Run: configure backup"
source "$BACKUP_CONF"

# The files mount comes up at login, perhaps before the network; give it a
# few minutes rather than writing into the empty folder underneath
for try in {1..10}; do
  mountpoint -q "$BACKUP_MOUNT" && break
  mount "$BACKUP_MOUNT" 2> /dev/null && break
  sleep 30
done
mountpoint -q "$BACKUP_MOUNT" || fail "Your Nextcloud files aren't mounted at $BACKUP_MOUNT."

export BORG_REPO
export BORG_PASSCOMMAND="secret-tool lookup coredesktop backup repo $BORG_REPO"

# Rebuilt by borg, or by reinstalling, so not worth the space
excludes=(
  "$HOME/.cache"
  "$HOME/.davfs2/cache"
  "$HOME/.local/share/Trash"
  "$HOME/.local/share/containers"
  "$HOME/.local/share/flatpak"
  "$HOME/.local/share/siblings"
  "$HOME/.local/share/coredesktop"
  "$HOME/.var/app/*/cache"
  "$HOME/.npm"
  "$HOME/.cargo/registry"
  "$HOME/go/pkg/mod"
)
exclude_args=(--exclude-caches)
for path in "${excludes[@]}"; do
  exclude_args+=(--exclude "sh:$path")
done
[ -f "$USER_EXCLUDE" ] && exclude_args+=(--exclude-from "$USER_EXCLUDE")

echo "Backing up $HOME to $BORG_REPO..."
# --one-file-system leaves out other mounts and btrfs subvolumes inside home
borg create --one-file-system --compression zstd --stats \
  "${exclude_args[@]}" "::{hostname}-{now:%Y-%m-%dT%H:%M}" "$HOME"
status=$?
# 1 is a warning, e.g. a file changed while it was read; the backup still exists
(( status <= 1 )) || fail "borg couldn't back up $HOME (exit $status). See: journalctl --user -u coredesktop-backup"

echo "Removing old backups..."
borg prune --glob-archives '{hostname}-*' \
  --keep-daily 7 --keep-weekly 4 --keep-monthly 6 \
  || fail "borg couldn't remove old backups. See: journalctl --user -u coredesktop-backup"
borg compact || fail "borg couldn't free space from old backups. See: journalctl --user -u coredesktop-backup"

echo "Backup finished."
exit 0
}