#!/bin/bash

# Exit script if command fails
set -e

# Display Help
Help() {
  echo
  echo "docker-volume-backup"
  echo "####################"
  echo
  echo "Description: Backup docker volumes."
  echo "Syntax: docker-volume-backup [-v|-a|-o|-c|help]"
  echo "Example: docker-volume-backup -v postgres_data01 -o /tmp -c postgres01"
  echo "options:"
  echo "  -v    Comma-separated list of volume names."
  echo "  -a    Backup all volumes."
  echo "  -o    Output directory. Defaults to '/var/tmp'"
  echo "  -c    Docker container name."
  echo "  help  Show docker-volume-backup manual."
  echo
}

# Show help and exit
if [[ $1 == 'help' ]]; then
    Help
    exit
fi

# Process params
while getopts ":a :c: :v: :o:" opt; do
  case $opt in
    a) ALL='true'
    ;;
    c) CONTAINER="$OPTARG"
    ;;
    v) VOLUMES="$OPTARG"
    ;;
    o) DIR="$OPTARG"
    ;;
    \?) echo "Invalid option -$OPTARG" >&2
    Help
    exit;;
  esac
done

# Fallback to environment vars and default values
: ${DIR:='/var/tmp'}

# Verify variables
[[ -z "$VOLUMES" ]] && [[ -z "$ALL" ]] && { echo "Parameter -v or -a|volumes or all must be set" ; exit 1; }
[[ -z "$DIR" ]] && { echo "Parameter -d|dir is empty" ; exit 1; }
[[ -z "$CONTAINER" ]] && { echo "Parameter -c|container is empty" ; exit 1; }

if $ALL ; then
  # Get all volumes from docker container
  VOLUME_LIST=($(docker inspect -f '{{ range .Mounts }}{{ .Name }} {{ end }}' $CONTAINER))

  # Concate volume list
  printf -v VOLUMES '%s,' "${VOLUME_LIST[@]}"
  VOLUMES="${VOLUMES%,}"
fi

if [[ ! -z $VOLUMES ]] ; then
  # Split volumes param values
  VOLUME_LIST=($(echo $VOLUMES | tr "," "\n"))
fi

# Create backup folder
mkdir -p ${DIR}/${CONTAINER}

# Cleanup backup folder
rm -rf ${DIR}/${CONTAINER}/*

# Create dump with docker for each database
for VOLUME in "${VOLUME_LIST[@]}"
do
  echo "Run backup for Docker volume $VOLUME"
  docker run --rm -v $VOLUME:/_data  -v ${DIR/./$(PWD)}/${CONTAINER}:/backup ubuntu tar cf /backup/$VOLUME.tar /_data
done

# Notify if backup has finished
echo "The Docker volume backup has finished: ${DIR}/${CONTAINER}/{${VOLUMES}}.tar"