#!/usr/bin/env bash
#
# Run a simple server health check.
#
# The script reports CPU load, memory usage, disk usage, network interfaces,
# listening ports, and the top processes by CPU and memory.
#
# Usage:
#   bash server_health_check.sh
#   bash server_health_check.sh --output /tmp/server-health.txt
#
# Options:
#   --output FILE   Save the report to a file.
#   --help          Show this help message.

set -Eeuo pipefail

output_file=""

usage() {
  sed -n '2,15p' "$0" | sed 's/^# \{0,1\}//'
}

section() {
  printf '\n===== %s =====\n' "$1"
}

run_report() {
  section "SERVER"
  printf 'Hostname: %s\n' "$(hostname)"
  printf 'Date: %s\n' "$(date '+%Y-%m-%d %H:%M:%S')"
  printf 'Uptime: %s\n' "$(uptime -p 2>/dev/null || uptime)"

  section "CPU"
  printf 'Load average: %s\n' "$(awk '{print $1, $2, $3}' /proc/loadavg)"
  if command -v top >/dev/null 2>&1; then
    top -bn1 | head -n 5
  fi

  section "MEMORY"
  free -h

  section "DISK"
  df -hT | grep -vE 'tmpfs|devtmpfs'

  section "NETWORK INTERFACES"
  if command -v ip >/dev/null 2>&1; then
    ip -brief address
  else
    ifconfig 2>/dev/null || true
  fi

  section "LISTENING PORTS"
  if command -v ss >/dev/null 2>&1; then
    ss -tulpen 2>/dev/null || ss -tulpen
  elif command -v netstat >/dev/null 2>&1; then
    netstat -tulpen 2>/dev/null || netstat -tulpn
  else
    printf 'Neither ss nor netstat is available.\n'
  fi

  section "TOP PROCESSES BY CPU"
  ps -eo pid,user,comm,%cpu,%mem --sort=-%cpu | head -n 11

  section "TOP PROCESSES BY MEMORY"
  ps -eo pid,user,comm,%cpu,%mem --sort=-%mem | head -n 11
}

while [[ "$#" -gt 0 ]]; do
  case "$1" in
    --output)
      output_file="${2:-}"
      shift 2
      ;;
    --help|-h)
      usage
      exit 0
      ;;
    *)
      printf 'ERROR: unknown option: %s\n' "$1" >&2
      usage >&2
      exit 1
      ;;
  esac
done

if [[ -n "$output_file" ]]; then
  run_report > "$output_file"
  printf 'Health check saved to %s\n' "$output_file"
else
  run_report
fi