backup

#!/bin/sh

# ==============================================================================
# Utilities
# ==============================================================================

_fatal() {
    echo "ERROR:" "$@" >&2
    exit 1
}

_fail() {
    _fatal "Last command failed, exiting"
}

_assert_set() {
    if [ -z "$1" ]; then
        _fatal "Value for environment variable \"$2\" missing"
    fi
}


# ==============================================================================
# rclone
# ==============================================================================

# Credits to https://gist.github.com/earthgecko/3089509
_random_string() {
    # shellcheck disable=SC2002
    cat /dev/urandom        | \
        tr -dc 'a-zA-Z0-9'  | \
        fold -w "$1"        | \
        head -n 1
}

RCLONE_MAX_TRY="${RCLONE_MAX_TRY:-5}"
RCLONE_PASSWORD=$(_random_string 32)
RCLONE_PORT=8888
RCLONE_USER=$(_random_string 32)

rclone_start() {
    _assert_set "$S3_ACCESS_KEY" S3_ACCESS_KEY
    _assert_set "$S3_ENDPOINT" S3_ENDPOINT
    _assert_set "$S3_PATH" S3_PATH
    _assert_set "$S3_REGION" S3_REGION
    _assert_set "$S3_SECRET_KEY" S3_SECRET_KEY
    if [ -z "${S3_PROVIDER}" ]; then
        S3_PROVIDER="AWS"
        echo "S3_PROVIDER not set, defaulting to '$S3_PROVIDER'"
    fi
    rclone config create s3 s3              \
        access_key_id "$S3_ACCESS_KEY"      \
        acl private                         \
        endpoint "$S3_ENDPOINT"             \
        env_auth false                      \
        force_path_style false              \
        region "$S3_REGION"                 \
        secret_access_key "$S3_SECRET_KEY"  \
        provider "$S3_PROVIDER"             \
        > /dev/null || _fail
    rclone serve restic                 \
        --addr localhost:"$RCLONE_PORT" \
        --user "$RCLONE_USER"           \
        --pass "$RCLONE_PASSWORD"       \
        s3:"$S3_PATH" || _fail &
    if [ "$1" = "no_check_rclone" ]; then
        echo "Not pinging rclone, waiting 5s"
        sleep 5
        return 0
    fi
    sleep 1
    for i in $(seq 1 "$RCLONE_MAX_TRY"); do
        echo "Attempting to connect to local rclone server ($i/$RCLONE_MAX_TRY)"
        if restic snapshots > /dev/null 2>&1; then
            return 0
        else
            sleep 2
        fi
    done
    _fatal "rclone server didn't start within $RCLONE_MAX_TRY tries, aborting"
}

# ==============================================================================
# restic
# ==============================================================================

export RESTIC_PASSWORD
export RESTIC_REPOSITORY="rest:http://$RCLONE_USER:$RCLONE_PASSWORD@localhost:$RCLONE_PORT"

# ==============================================================================
# main
# ==============================================================================

backup() {
    ROOTFS_PATH="${ROOTFS_PATH:-/rootfs}"
    rclone_start
    restic backup "$ROOTFS_PATH" || _fail
    restic forget --keep-within "${RESTIC_DURATION:-10y}" || _fail
}

help() {
    echo "Usage: $0 [command]

Available commands:
    backup          Backups the volume to the restic repository
    help            Prints this message and exit
    init            Inits the restic repository
    restic [cmd]    Executes a restic command
    restore [id]    Empties the volume (!), and restores snapshot [id]
    snapshots       Lists available snapshots
"
}

init() {
    rclone_start "no_check_rclone"
    restic init || _fail
}

restic_cmd() {
    ROOTFS_PATH="${ROOTFS_PATH:-/rootfs}"
    rclone_start
    restic "$@" || _fail
}

restore() {
    ROOTFS_PATH="${ROOTFS_PATH:-/rootfs}"
    SNAPSHOT_ID="${1:-latest}"
    for ITEM in "$ROOTFS_PATH"/*; do rm -rf "$ITEM" || _fail; done
    rclone_start
    restic restore "$SNAPSHOT_ID"   \
        --path "$ROOTFS_PATH"       \
        --target /                  \
        || _fail
}

snapshots() {
    rclone_start
    restic snapshots || _fail
}

COMMAND=$1
case $COMMAND in
    backup|init|restore|snapshots)
        shift
        $COMMAND "$@"
        ;;
    restic)
        shift
        restic_cmd "$@"
        ;;
    *)
        help
        ;;
esac