#!/bin/bash

## Set NO_DOCKER_RESTART to prevent restarting docker after upgrade.
## Set ALLOW_DOCKER_CHANGE to allow change your docker version.
## Set TARGET_DOCKER_VERSION to force a version (use cautiously!)

distro=$(lsb_release -is)
release=$(lsb_release -rs)

if [ -z "$TARGET_DOCKER_VERSION" ]; then
    case "$distro" in
        Debian)
            case "$release" in
                10|11|12) target_version=24;;
                *) target_version=19;;
            esac
            ;;
        Ubuntu)
            case "$release" in
                22.04) target_version=24;;
                *) target_version=19;;
            esac
            ;;
        *) target_version=17;;
    esac
else
    target_version="$TARGET_DOCKER_VERSION"
fi


just_installed=
if ! type -p docker >/dev/null; then
    echo "Installing docker..."
    type -p curl >/dev/null ||
        apt-get install -y curl </dev/null

    curl -sSL https://get.docker.io | sh || exit 1
    just_installed=1
fi

read docker_client_version docker_server_version < <(
    docker version --format '{{.Client.Version}} {{.Server.Version}}'
)

mismatch_client_server=
## issue a warning if client and server versions are different
if [ "$docker_client_version" != "$docker_server_version" ]; then
    echo "WARNING: docker client and server versions differ!" >&2
    echo "  client: $docker_client_version" >&2
    echo "  server: $docker_server_version" >&2
    mismatch_client_server=1
fi

distrib_available_version="$(apt-cache madison docker-ce |
                       cut -f 2 -d \| |
                       grep "$target_version" |
                       head -n 1 | xargs echo)"

cleaned_distrib_available_version="${distrib_available_version%%~*}"
cleaned_distrib_available_version="${distrib_available_version%-*}"
cleaned_distrib_available_version="${cleaned_distrib_available_version#*:}"
if [ -z "$mismatch_client_server" ] &&
       [[ "$docker_client_version" == "$cleaned_distrib_available_version" ]]; then
    ## current and target versions match, no upgrade needed
    echo "INFO: recommended target docker version $docker_client_version already installed" >&2
    echo "  To set a different target version, set TARGET_DOCKER_VERSION" >&2
    exit 0
fi

## Should we skip upgrade?
if [ -z "$just_installed" ] && [ -z "$ALLOW_DOCKER_CHANGE" ]; then
    if [ -n "$distrib_available_version" ]; then
        if [ -z "$mismatch_client_server" ]; then
            ## get current version for docker-ce debian package installed
            current_debian_package_version="$(dpkg -s docker-ce | grep '^Version:' | cut -f 2 -d ' ')"
            echo "INFO: docker recommended version available (current: $current_debian_package_version => recommended: $distrib_available_version)" >&2
        else
            current_docker_ce_package_version="$(dpkg -s docker-ce | grep '^Version:' | cut -f 2 -d ' ')"
            current_docker_ce_cli_package_version="$(dpkg -s docker-ce-cli | grep '^Version:' | cut -f 2 -d ' ')"
            echo "WARNING: docker recommended version available (recommended: $distrib_available_version)" >&2
            echo "  And your client ($current_docker_ce_cli_package_version) and server ($current_docker_ce_package_version) versions differ." >&2
        fi
        echo "  To change version, run this script with ALLOW_DOCKER_CHANGE=1" >&2
    else
        echo "WARNING: your docker version does match target recommended version" >&2
        echo "  And your distribution does not package target version." >&2
        echo "  - Your distribution: $distro $release" >&2
        echo "  - Current docker version: $docker_client_version" >&2
        echo "  - Target recommended version: ${target_version}*" >&2
    fi
    exit 0
fi

if [ -z "$distrib_available_version" ]; then
    echo "ERROR: no docker version matching '${target_version}*' available for your distribution" >&2
    echo "  Your distribution: $distro $release" >&2
    echo "  Available versions:" >&2
    apt-cache madison docker-ce | cut -f 2 -d \| | sed -r 's/^/  -/g' >&2
    echo
    echo "  1) You may need to contact your system administrator to upgrade this script." >&2
    echo "  2) Meanwhile, if you know what you are doing, you can set yourself a target version" >&2
    echo "     by setting TARGET_DOCKER_VERSION." >&2
    exit 1
fi

apt-get install -y --allow-downgrades \
        docker-ce="$distrib_available_version" \
        docker-ce-cli="$distrib_available_version" </dev/null &&
    if [ -z "$NO_DOCKER_RESTART" ]; then
        systemctl daemon-reload &&
            service docker restart
    fi