#!/bin/bash

set -e

VERSION=$(curl -s https://api.github.com/repos/prometheus/alertmanager/releases | python3 -c 'import json,sys;print(json.load(sys.stdin)[0]["tag_name"])' | sed 's/v//')
OS=$(uname -s | tr '[:upper:]' '[:lower:]')
ARCH=$(uname -m | sed 's/x86_/amd/')

trap "rm -rf alertmanager*" EXIT

pushd /tmp
filename="alertmanager-${VERSION}.${OS}-${ARCH}.tar.gz"
echo "Downloading version ${filename}"
wget https://github.com/prometheus/alertmanager/releases/download/v${VERSION}/$filename
tar xvfz $filename
cd alertmanager-*/
chmod +x ./alertmanager
mv ./alertmanager /usr/sbin/
mkdir -p /etc/alertmanager
cp alertmanager.yml /etc/alertmanager/
cat <<EOF >/etc/systemd/system/alertmanager.service
[Unit]
Description=Alertmanager
Wants=network-online.target
After=network-online.target

[Service]
User=alertmanager
Group=alertmanager
Type=simple
WorkingDirectory=/etc/alertmanager/
ExecStart=/usr/sbin/alertmanager --config.file=/etc/alertmanager/alertmanager.yml --web.external-url http://0.0.0.0:9093

[Install]
WantedBy=multi-user.target
EOF

useradd -r alertmanager
chown -R alertmanager:alertmanager /etc/alertmanager

systemctl enable alertmanager.service
systemctl start alertmanager.service

popd