#!/bin/bash

need_restart=
if ! type -p docker; then
    echo "Installing docker..."
    curl -sSL https://get.docker.io | sh
fi

docker_version=17
if ! [[ "$(docker --version)" == "Docker version $docker_version"* ]]; then
    version="$(apt-cache madison docker-ce | cut -f 2 -d \| | grep "$docker_version" | head -n 1 | xargs echo)"
    ## DOWNGRADE to 17.xx because 18.xx do not support registry v1
    apt-get install -y --force-yes docker-ce="$version"
    need_restart=true
fi

if [ "$need_restart" ]; then
    systemctl daemon-reload &&
        service docker restart
fi