#!/usr/bin/env bash

set -euo pipefail

dir="$(mktemp -d)"
pushd .
cd "${dir}"

BINARY=$(curl https://api.github.com/repos/prometheus/node_exporter/releases/latest | jq -r '.assets[] | select(.name | contains("linux-amd64")) | .browser_download_url')
curl -L $BINARY -o node-exporter.tgz

mkdir -p prometheus/usr/{bin,lib/{systemd/system,extension-release.d}}
tar xzf node-exporter.tgz

cp -vrf node_exporter-*/node_exporter prometheus/usr/bin/node_exporter
cat > /etc/systemd/system/prometheus-node-exporter.service <<- EOM
[Unit]
Description=Prometheus exporter for machine metrics
Requires=network-online.target
After=network-online.target

[Service]
Restart=on-failure
ExecStart=/usr/bin/node_exporter
ExecReload=/bin/kill -HUP \$MAINPID
NoNewPrivileges=true
ProtectHome=read-only
ProtectSystem=strict

[Install]
WantedBy=multi-user.target
EOM

source /etc/os-release
echo -e "SYSEXT_LEVEL=1.0\nID=steamos\nVERSION_ID=${VERSION_ID}" >> prometheus/usr/lib/extension-release.d/extension-release.prometheus-node-exporter

mkdir -p /var/lib/extensions
rm -rf /var/lib/extensions/prometheus-node-exporter
cp -vrf prometheus /var/lib/extensions/prometheus-node-exporter

popd
rm -rf "${dir}"