#!/usr/bin/env bash

set -eEuo pipefail

readonly REPO_DIR="/opt/fapg/fapg-daq"
readonly RECORDER_BIN="${REPO_DIR}/roles/daq-recorder/bin/fapg-daq-mqtt-sqlite"
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
readonly SCRIPT_DIR

readonly SERVICE_NAME="fapg-daq-mqtt-sqlite.service"
readonly SERVICE_FILE="/etc/systemd/system/${SERVICE_NAME}"

readonly ENV_DIR="/etc/fapg-daq"
readonly ENV_FILE="${ENV_DIR}/mqtt-sqlite.env"

readonly STATE_DIR="/var/lib/fapg-daq"
readonly RUN_USER="fapg-daq"
readonly RUN_GROUP="fapg-daq"

readonly MQTT_HOST="10.77.0.2"
readonly MQTT_PORT="1883"
readonly MQTT_USERNAME="fapg_vps"
readonly MQTT_TOPIC="fapg/daq/#"
MQTT_PASSWORD=""

function die() {
    echo "ERROR: $*" >&2
    exit 1
}

function require_root() {
    if [[ "$(id -u)" -ne 0 ]]; then
        die "$0 requires superuser privileges."
    fi
}

function install_os_dependencies() {
    apt-get update
    apt-get install -y \
        perl \
        sqlite3 \
        libdbi-perl \
        libdbd-sqlite3-perl \
        libnet-mqtt-simple-perl
}

function create_runtime_user() {
    if ! getent group "${RUN_GROUP}" > /dev/null; then
        addgroup --system "${RUN_GROUP}"
    fi

    if ! id "${RUN_USER}" > /dev/null 2>&1; then
        adduser \
            --system \
            --ingroup "${RUN_GROUP}" \
            --home "${STATE_DIR}" \
            --no-create-home \
            --disabled-login \
            "${RUN_USER}"
    fi

    mkdir -p "${STATE_DIR}"
    chown "${RUN_USER}:${RUN_GROUP}" "${STATE_DIR}"
}

function check_repo_layout() {
    [[ -d "${REPO_DIR}" ]] || die "Repo not found at ${REPO_DIR}."
    [[ -x "${RECORDER_BIN}" ]] || die "${RECORDER_BIN} does not exist or is not executable."
}

function write_env_file() {
    mkdir -p "${ENV_DIR}"

    if [[ -f "${ENV_FILE}" ]]; then
        echo "${ENV_FILE} already exists; leaving it unchanged."
        chown root:"${RUN_GROUP}" "${ENV_FILE}"
        chmod 0640 "${ENV_FILE}"
        return
    fi

    if [[ -z "${MQTT_PASSWORD:-}" ]]; then
        read -rsp "MQTT password for user '${MQTT_USERNAME}': " MQTT_PASSWORD
        echo
    fi

    [[ -n "${MQTT_PASSWORD:-}" ]] || die "MQTT_PASSWORD is required."

    cat > "${ENV_FILE}" <<EOF
MQTT_SIMPLE_ALLOW_INSECURE_LOGIN=1

MQTT_HOST=${MQTT_HOST}
MQTT_PORT=${MQTT_PORT}
MQTT_USERNAME=${MQTT_USERNAME}
MQTT_PASSWORD=${MQTT_PASSWORD}
MQTT_TOPIC=${MQTT_TOPIC}

FAPG_DAQ_DB=${STATE_DIR}/readings.sqlite3
EOF

    chown root:"${RUN_GROUP}" "${ENV_FILE}"
    chmod 0640 "${ENV_FILE}"
}

function write_systemd_service() {
    install -m 0644 -o root -g root \
        "${SCRIPT_DIR}/etc/systemd/system/fapg-daq-mqtt-sqlite.service" \
        "${SERVICE_FILE}"
}

function enable_service() {
    systemctl daemon-reload
    systemctl enable "${SERVICE_NAME}"
    systemctl restart "${SERVICE_NAME}"
}

function show_status() {
    cat <<"EOF"
Deployment complete.
Current service state:
EOF
    systemctl --no-pager --full status "${SERVICE_NAME}"
}

function main() {
    require_root
    install_os_dependencies
    create_runtime_user
    check_repo_layout
    write_env_file
    write_systemd_service
    enable_service
    show_status
}

main "$@"