#!/usr/bin/env bash

# Exit if not run as root
if [ "$EUID" -ne 0 ]; then
  echo "Please run as root (use sudo)."
  exit 1
fi

# Variables
DOWNLOAD_URL="https://github.com/prometheus/node_exporter/releases/download/v1.9.1/node_exporter-1.9.1.linux-amd64.tar.gz"
TAR_FILE="node_exporter-1.9.1.linux-amd64.tar.gz"
EXTRACTED_DIR="node_exporter-1.9.1.linux-amd64"

# Download file
echo "Downloading Node Exporter..."
curl -L -o "$TAR_FILE" "$DOWNLOAD_URL"
if [ $? -ne 0 ]; then
  echo "Download failed. Exiting."
  exit 1
fi

# Remove old user and group if exists
if id "node_exporter" &>/dev/null; then
  echo "User node_exporter exists, deleting..."
  userdel node_exporter
fi
groupadd -f node_exporter
useradd -g node_exporter --no-create-home --shell /bin/false node_exporter

# Create required directories
mkdir -p /etc/node_exporter
chown node_exporter:node_exporter /etc/node_exporter

# Extract package
tar -xzf "$TAR_FILE"
if [ $? -ne 0 ]; then
  echo "Extraction failed. Exiting."
  exit 1
fi

# Install binary
cp "$EXTRACTED_DIR/node_exporter" /usr/bin/
chown node_exporter:node_exporter /usr/bin/node_exporter

# Cleanup downloaded files and extracted folder
echo "Cleaning up temporary files..."
rm -f "$TAR_FILE"
rm -rf "$EXTRACTED_DIR"

# Create systemd service
cat <<EOF > /etc/systemd/system/node_exporter.service
[Unit]
Description=Node Exporter
Documentation=https://prometheus.io/docs/guides/node-exporter/
Wants=network-online.target
After=network-online.target

[Service]
User=node_exporter
Group=node_exporter
Type=simple
Restart=on-failure
ExecStart=/usr/bin/node_exporter --web.listen-address=:9100

[Install]
WantedBy=multi-user.target
EOF

# Reload systemd, enable and start service
systemctl daemon-reload
systemctl enable node_exporter
systemctl start node_exporter

# Verify service by checking HTTP status code
echo "Verifying Node Exporter..."
sleep 2
STATUS_CODE=$(curl -s -o /dev/null -w "%{http_code}" http://localhost:9100/metrics)

if [ "$STATUS_CODE" -eq 200 ]; then
  echo "Node Exporter is running and reachable."
else
  echo "Node Exporter verification failed. HTTP status code: $STATUS_CODE"
  exit 1
fi

echo "Installation completed successfully."