#!/usr/bin/env bash

# Script to install fluent-bit on ubuntu based off of instructions from
# https://docs.fluentbit.io/manual/installation/linux/ubuntu
# The binary is td-agent-bit and will be in /opt/td-agent-bit/bin/

# https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html
set -o errexit   # exit script if a command fails
set -o nounset   # exit script if a varialbe is undeclared
set -o pipefail  # do not hide errors within pipes

[[ $(id -u) -ne 0 ]] && echo "This script must run as root" && exit 1

os_type_error="Error: This script is only supported on ubuntu focal, bionic or xenial"
fb_url="https://packages.fluentbit.io"
fb_bin="td-agent-bit"
fb_dir="/etc/td-agent-bit"
fb_config="./td-agent-bit.conf"
fb_parsers="./parsers.conf"
fb_secret="./creds.json"
if [[ ! -f "${fb_config}" || ! -f "${fb_parsers}" || ! -f "${fb_secret}" ]]; then
    echo "required files are missing: ${fb_config} ${fb_parsers} ${fb_secret}"
    exit 1
fi

# source the env variables which tells us which version of ubnutu we're on(focal/bionic/xenial)
if [[ -r /etc/os-release ]]; then
    # shellcheck disable=SC1091
    . /etc/os-release
    case "${UBUNTU_CODENAME}" in
    "focal" | "bionic" | "xenial")
        ;;
    *)
        echo "${os_type_error}. Found version ${UBUNTU_CODENAME}"
        exit 1
    ;;
    esac
else
    echo "${os_type_error}"
    exit 1
fi

# add the fluentbit gpg key so we can apt-get the signed td-agent-bit package
if ! wget -qO - "${fb_url}"/fluentbit.key | apt-key add - ; then
    echo "There was a problem adding fluentbit.key"
    exit 1
fi

sources_file="/etc/apt/sources.list"
sources_string="deb ${fb_url}/ubuntu/${UBUNTU_CODENAME} ${UBUNTU_CODENAME} main"
echo "checking ${sources_file} for ${sources_string}"
if ! grep -q "${sources_string}" "${sources_file}"; then
    echo "Updating ${sources_file} with ${sources_string}"
    echo "${sources_string}" >> "${sources_file}"
fi

apt-get update -y

echo "checking if we can download ${fb_bin} from ${fb_url}"
apt-get -qq --dry-run install "${fb_bin}"
# an apt-get error here could indicate an expired root certificate
# https://docs.fluentbit.io/manual/installation/linux/ubuntu#certificate-issue
if [ $? == 100 ]; then
    apt-get install ca-certificates -y
fi

echo "installing ${fb_bin}"
apt-get install "${fb_bin}" -y

echo "copying fluent-bit configs to ${fb_dir}"
cp "${fb_config}" "${fb_parsers}" "${fb_secret}" "${fb_dir}"

echo "staring the ${fb_bin} service"
service "${fb_bin}" start
service "${fb_bin}" status