#!/usr/bin/env bash
#
# Borg script for home folder backups.
# Adapted from https://borgbackup.readthedocs.io/en/stable/quickstart.html#automating-backups
#
# See also: https://borgbackup.readthedocs.io/en/stable/faq.html#if-a-backup-stops-mid-way-does-the-already-backed-up-data-stay-there
#           https://borgbackup.readthedocs.io/en/stable/usage/help.html#borg-help-placeholders
#
# Copyright (C) 2019 Silvio Rhatto - rhatto at riseup.net
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published
# by the Free Software Foundation, either version 3 of the License,
# or any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

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

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

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

# Display usage
function borger_usage {
  echo "usage: $BASENAME <destination> [--continuous|--list|--check|--info]"
  echo -n "available destinations from $BASE_CONFIG: "
  ls $BASE_CONFIG
  exit 1
}

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

  # Check config
  if [ ! -e "$CONFIG" ]; then
    fatal "No such config $CONFIG"
    exit 1
  elif [ -d "$CONFIG" ]; then
    MULTIPLE="yes"
  fi

  # Lockfile location
  LOCKFILE="$TMP/$BASENAME/$DESTINATION.lock"
}

# Process configuration
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"
  KEEPMONTHLY="6"
  ENCRYPTION="keyfile"
  PLACEHOLDER="{user}"

  source $CONFIG

  # 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
}

# List
function borger_list {
  borg list
  exit $?
}

# Check
function borger_check {
  borg check
  exit $?
}

# Info
function borger_info {
  borg info
  exit $?
}

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

# Initialize
function borger_init {
  if [ ! -z "$SSH_SERVER" ]; then
    # Remote backup over SSH
    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 [ "$init_exit" != "0" ]; then
        fatal "Error initializing repository"
      fi
    fi
  else
    # Local backup
    if [ ! -f "$BORG_REPO/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
  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
    info "Error pruning repository"
    info "Trying to break the lockfile..."
    borg break-lock $BORG_REPO
  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
}

# Create lockfile
function borger_set_lockfile {
  if [ ! -z "$LOCKFILE" ]; then
    mkdir -p `dirname $LOCKFILE`
    if ( set -o noclobber; echo "$$" > "$LOCKFILE" ) &> /dev/null; then
      trap 'borger_unset_lockfile' INT TERM EXIT
    else
      fatal "Could not create lockfile $LOCKFILE, exiting"
    fi
  fi
}

# Remove lockfile
function borger_unset_lockfile {
  if [ ! -z "$LOCKFILE" ]; then
    rm -f $LOCKFILE || echo "Could not remove lockfile $LOCKFILE"
  fi
}

# Check lockfile
function borger_check_lockfile {
  local pid process

  if [ ! -z "$LOCKFILE" ] && [ -f "$LOCKFILE" ]; then
    pid="`cat $LOCKFILE`"
    process="`ps --no-headers -o comm $pid`"
    if [ "$?" == "0" ] && [ "`ps --no-headers -o comm $$`" == "$process" ]; then
      fatal "Another program is running for $LOCKFILE, skipping run"
    else
      echo "Found old lockfile $LOCKFILE, removing it"
      borger_unset_lockfile
    fi
  fi
}

# Main backup procedure
function borger_run {
  borger_check_lockfile
  borger_set_lockfile

  # Run for single or multiple destinations
  if [ "$MULTIPLE" == "yes" ]; then
    borger_multiple
  else
    borger_config
    borger_trap
    borger_init
    borger_create
    borger_prune
    borger_exit
  fi
}

# Run for a single destination
function borger_single {
  borger_config

  # Convert the pass command to passphrase otherwise
  # the user would be interrupted by a passphrase prompt
  # at every iteration
  if [ ! -z "$BORG_PASSCOMMAND" ] && [ -z "$BORG_PASSPHRASE" ]; then
    info "Asking passphrase for borg key used at $DESTINATION"
    export BORG_PASSPHRASE="`$BORG_PASSCOMMAND`"
    export BORG_PASSCOMMAND=""
  fi

  # Run as a subprocess so we do not exit on any fatal error
  $FULLNAME $DESTINATION
}

# Run for multiple destinations
function borger_multiple {
  info "Multiple destination \"$DESTINATION\" found. Processing each subconfig..."

  # Evaluate each config
  for config in `ls $CONFIG`; do
    # Include BORG_PASSPHRASE config for each destination in an array
    if grep -q "BORG_PASSCOMMAND" $CONFIG/$config; then
      # Ask the passphrase only once
      if [ -z "${BORG_PASSPHRASES[$config]}" ]; then
        info "Asking passphrase for borg key used at $config"
        COMMAND="`grep BORG_PASSCOMMAND $CONFIG/$config | cut -d = -f 2 | sed -e "s/^'//" -e "s/'$//" -e 's/^"//' -e 's/"$//'`"
        #BORG_PASSPHRASES[$config]="BORG_PASSPHRASE=`$COMMAND`"
        BORG_PASSPHRASES[$config]="`$COMMAND`"
      fi
    else
      BORG_PASSPHRASES[$config]=""
    fi
  done

  # Serial approach
  for config in `ls $CONFIG`; do
    info "Calling borger for $DESTINATION/$config..."
    export BORG_PASSCOMMAND=""
    export BORG_PASSPHRASE="${BORG_PASSPHRASES[$config]}"
    $FULLNAME $DESTINATION/$config 2>&1 | sed -e "s/^\[borger\]/[borger] [$config]/" -e "s/^\([^\[]\)/[borger] [$config] \1/"
  done

  # Parallel approach
  ## Config is a folder, so we iterate over all items
  ## and call borger for each config in parallel
  #for config in `ls $CONFIG`; do
  #  info "Calling borger for $DESTINATION/$config..."
  #  (
  #    export BORG_PASSPHRASE="${BORG_PASSPHRASES[$config]}"
  #    $FULLNAME $DESTINATION/$config $MULTIPLE_OPTION 2>&1 | sed -e "s/^\[borger\]/[borger] [$config]/" -e "s/^\([^\[]\)/[borger] [$config] \1/"
  #  ) &
  #done

  ## Since we dispatched everything to subprocesses,
  ## there's nothing to do here.
  ##exit
  #wait
}

# Exit procedure
function borger_exit {
  # Use highest exit code as global exit code
  global_exit=$(( backup_exit > prune_exit ? backup_exit : prune_exit ))

  if [ ${global_exit} -eq 1 ]; then
    info "Backup and/or Prune finished with a warning"
  fi

  if [ ${global_exit} -gt 1 ]; then
    info "Backup and/or Prune finished with an error"
  fi

  exit ${global_exit}
}

# Continuous backup processing
function borger_continuous {
  borger_check_lockfile
  borger_set_lockfile

  # Run until interruption
  while true; do
    if [ "$MULTIPLE" == "yes" ]; then
      borger_multiple
    else
      borger_single
    fi

    # Wait
    info "Running on continous mode... sleeping $INTERVAL..."
    sleep $INTERVAL
  done
}

# Strong requirement: bash 4
# https://stackoverflow.com/questions/1494178/how-to-define-hash-tables-in-bash
if echo $BASH_VERSION | grep -q "^3"; then
  fatal "$BASENAME requires bash 4 or newer."
fi

# Declare global passphrase array
declare -A BORG_PASSPHRASES

# Setup
borger_setup

# Dispatch
if [ -z "$DESTINATION" ]; then
  borger_usage
elif [ -z "$OPTION" ]; then
  borger_run
elif [ "$OPTION" == "--list" ]; then
  borger_config
  borger_list
elif [ "$OPTION" == "--check" ]; then
  borger_config
  borger_check
elif [ "$OPTION" == "--info" ]; then
  borger_config
  borger_info
elif [ "$OPTION" == "--continuous" ]; then
  borger_continuous
fi