#!/usr/bin/env bash

set -eEuo pipefail

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

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

readonly ENV_DIR="/etc/fapg-daq"
readonly ENV_FILE="${ENV_DIR}/daq.conf"

readonly STATE_DIR="/var/lib/fapg-daq"
readonly RUN_DIR="/run/fapg-daq"

readonly RUN_USER='fapg-daq'
readonly RUN_GROUP='fapg-daq'

readonly SERIAL_DEVICE=''
readonly READ_INTERVAL=5
readonly MQTT_HOST='fapg-daq-five-01'
readonly MQTT_PORT='1883'
readonly MQTT_USERNAME='fapg_zero'
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 \
	    libnet-mqtt-simple-perl \
	    libdevice-serialport-perl

    echo "Installed all OS dependencies."
}

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

    # USB serial devices are normally accessible to members of dialout.
    usermod -aG dialout "${RUN_USER}"

    echo "Created runtime user ${RUN_USER}, group ${RUN_GROUP}."
}

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

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

    echo "Verified layout of repo at ${REPO_DIR}."
}

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

    # TODO: print diff of existing and proposed env file
    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."

    # TODO: unsafe!
    cat > "${ENV_FILE}" <<EOF
MQTT_SIMPLE_ALLOW_INSECURE_LOGIN=1

READ_INTERVAL=${READ_INTERVAL}
MQTT_HOST="${MQTT_HOST}"
MQTT_PORT="${MQTT_PORT}"
MQTT_USERNAME="${MQTT_USERNAME}"
MQTT_PASSWORD="${MQTT_PASSWORD}"
EOF

    if [[ -n "${SERIAL_DEVICE}" ]]; then
        echo "SERIAL_DEVICE=\"${SERIAL_DEVICE}\"" >> "${ENV_FILE}"
    fi

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

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

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

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

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

main "$@"