#!/usr/bin/env bash
# Backs up what MIGRATION.md section 1 lists to the Kingston SATA SSD (sda):
# the built system and disko script, WoW's settings and addons, and the home
# folder. Safe to run again: the first run formats the drive (only if it is
# empty), later runs only copy what changed.
#
#   sudo ~/git/dot/tools/backup-to-sata
set -euo pipefail

disk=/dev/disk/by-id/ata-KINGSTON_SA400S37120G_50026B76820FD3CE
mnt=/mnt/backup
user=vizie
home=/home/$user
repo=$home/git/dot
wow="$home/Games/battlenet/drive_c/Program Files (x86)/World of Warcraft/_retail_"

if [ "$EUID" -ne 0 ]; then
  echo "Run it with sudo: sudo $0" >&2
  exit 1
fi
if [ ! -e "$disk" ]; then
  echo "The Kingston drive ($disk) isn't there." >&2
  exit 1
fi

# Format only a drive with nothing on it, or reuse the backup drive from an
# earlier run. Anything else (partitions, another file system) stops here.
label=$(blkid -o value -s LABEL "$disk" || true)
fstype=$(blkid -o value -s TYPE "$disk" || true)
parts=$(lsblk -n -o NAME "$disk" | wc -l)
if [ "$fstype" = btrfs ] && [ "$label" = backup ]; then
  echo "== Backup drive already formatted, updating it"
elif [ -z "$fstype" ] && [ "$parts" -eq 1 ]; then
  echo "== Formatting $(readlink -f "$disk") (empty Kingston SSD) as 'backup'"
  mkfs.btrfs -L backup "$disk"
  udevadm settle
else
  echo "The Kingston drive has something on it ($fstype${label:+, label $label}); not touching it." >&2
  exit 1
fi

mkdir -p "$mnt"
if ! mountpoint -q "$mnt"; then
  mount -o compress=zstd /dev/disk/by-label/backup "$mnt"
fi
install -d -o "$user" "$mnt/nix-cache" "$mnt/wow"

echo "== Saving the built system and the disko script"
sudo -u "$user" bash -euo pipefail -c '
  cd "$1"
  sys=$(nix build --no-link --print-out-paths .#nixosConfigurations.desktop.config.system.build.toplevel)
  disko=$(nix build --no-link --print-out-paths .#nixosConfigurations.desktop.config.system.build.diskoScript)
  nix copy --to "file://$2/nix-cache?compression=zstd" "$sys" "$disko"
  echo "$sys" > "$2/nix-cache/system"
  echo "$disko" > "$2/nix-cache/disko"
' _ "$repo" "$mnt"

echo "== WoW settings and addons"
rsync -a --delete "$wow/WTF" "$wow/Interface" "$mnt/wow/"

echo "== Home folder (about 83 GB the first time)"
rsync -aHAXx --delete --info=progress2 --filter="merge $repo/backup-filter" "$home/" "$mnt/$user/"

sync
echo "== Done"
du -sh "$mnt"/*
df -h "$mnt"
umount "$mnt"