#!/bin/bash
#
# Borg script for home folder backups.
# Adapted from https://borgbackup.readthedocs.io/en/stable/quickstart.html#automating-backups

# Parameters
BASENAME="`basename $0`"
DESTINATION="$1"
OPTION="$2"
BASE_CONFIG="$HOME/.config/borger"
CONFIG="$BASE_CONFIG/$DESTINATION"

# Print info
function info {
  printf "[$BASENAME] [%s] %s\n" "$(date)" "$*" >&2;
}

# Fata error
function fatal {
  info [fatal] $*
  exit 1;
}

function borger_usage {
  # Ensure we have our base config folder
  mkdir -p $BASE_CONFIG

  # List available targets
  if [ -z "$DESTINATION" ]; then
    echo "usage: $BASENAME <destination> [--check]"
    echo -n "available destinations from $BASE_CONFIG: "
    ls $BASE_CONFIG
    exit 1
  fi
}

# Config
function borger_config {
  # Ensure we have an username
  if [ -z "$USER" ]; then
    USER="`whoami`"
  fi

  # In case your home folder is a symlink
  if [ ! -z "`readlink $HOME`" ]; then
    ORIG="`readlink $HOME`"
  else
    ORIG="$HOME"
  fi

  # Default backup config
  keepdaily="7"
  keepweekly="4"
  keepmonth="6"
  encryption="keyfile"
  placeholder="{user}"

  if [ -e "$CONFIG" ] ; then
    source $CONFIG
  else
    fatal "No such config $CONFIG"
  fi

  # Setting this, so the repo does not need to be given on the commandline:
  if [ -z "$BORG_REPO" ]; then
    export BORG_REPO_DIR="/var/backups/users/$USER/borg"
    export BORG_REPO="ssh://$SSH_SERVER:$SSH_PORT/$BORG_REPO_DIR"
  fi
}

# Check
function borger_check {
  if [ "$OPTION" == "--check" ]; then
    borg list
    exit $?
  fi
}

# Our trap
function borger_trap {
  trap 'info Backup interrupted >&2; exit 2' INT TERM
}

# Initialize
function borger_init {
  if ! ssh $SSH_SERVER -p $SSH_PORT test -f $BORG_REPO_DIR/config; then
    info "Initializing borg repository at $BORG_REPO..."
    borg init --encryption=$encryption $BORG_REPO

    init_exit=$?

    if [ "$init_exit" != "0" ]; then
      fatal "Error initializing repository"
    fi
  fi
}

# Backup the most important directories into an archive named after
# the machine this script is currently running on:
function borger_create {
  info "Starting backup..."

  borg create                \
    --verbose                \
    --filter AME             \
    --list                   \
    --stats                  \
    --show-rc                \
    --compression lz4        \
    --exclude-caches         \
    ::"${placeholder}-{now}" \
    $ORIG

  backup_exit=$?

  if [ "$backup_exit" != "0" ]; then
    fatal "Error creating snapshot"
  fi
}

# Use the `prune` subcommand to maintain daily, weekly and monthly archives.
# The '${placeholder}-' prefix is very important to limit prune's operation to
# one specific archive and not apply to archives also.
function borger_prune {
  info "Pruning repository..."
  borg prune                     \
    --list                       \
    --prefix "${placeholder}-"   \
    --show-rc                    \
    --keep-daily    $keepdaily   \
    --keep-weekly   $keepweekly  \
    --keep-monthly  $keepmonthly \

    prune_exit=$?

  if [ "$prune_exit" != "0" ]; then
    fatal "Error pruning repository"
  fi
}

# Main
borger_usage
borger_config
borger_check
borger_trap
borger_init
borger_create
borger_prune