#!/usr/bin/env bash

# State management
get_state_file() {
  echo "/tmp/chorus-monitoring-down-hosts.txt"
}

is_host_down() {
  local type=$1 host=$2
  local state_file=$(get_state_file)

  # If state file doesn't exist, host is not down
  [ ! -f "$state_file" ] && return 1

  # Check if TYPE:HOST exists in state file
  grep -qxF "${type}:${host}" "$state_file"
}

mark_host_down() {
  local type=$1 host=$2
  local state_file=$(get_state_file)

  # Create file if it doesn't exist
  touch "$state_file"

  # Only add if not already present (idempotent)
  if ! grep -qxF "${type}:${host}" "$state_file"; then
    echo "${type}:${host}" >> "$state_file"
  fi
}

mark_host_up() {
  local type=$1 host=$2
  local state_file=$(get_state_file)

  # If state file doesn't exist, nothing to remove
  [ ! -f "$state_file" ] && return 0

  # Remove the TYPE:HOST line from state file
  sed -i "\|^${type}:${host}$|d" "$state_file"
}

notify() {
  local status=$1 type=$2 host=$3
  local emoji message

  if [[ "$status" == "DOWN" ]]; then
    emoji="🔴"
    message="$emoji [$type] $HOSTNAME says $host is DOWN. $(date -u)"
  else
    emoji="🟢"
    message="$emoji [$type] $HOSTNAME says $host is UP. $(date -u)"
  fi

  curl -s -d "$message" \
    https://ntfy.uphillsecurity.com/thisisarandomtpic
  # ADD MAIL AND OTHER METHODS HERE
}

check_with_retries() {
  local type=$1 host=$2; shift 2

  for _ in {1..5}; do
    if "$@"; then
      echo "$host: reply"

      # Check if host was previously down (state transition: DOWN → UP)
      if is_host_down "$type" "$host"; then
        mark_host_up "$type" "$host"
        notify "UP" "$type" "$host"
      fi

      return 0
    fi
    sleep 1
  done

  echo "$host: no reply after 5 attempts"

  # Check if host is newly down (state transition: UP → DOWN)
  if ! is_host_down "$type" "$host"; then
    mark_host_down "$type" "$host"
    notify "DOWN" "$type" "$host"
  fi

  return 1
}

main() {

  # WHAT TO MONITOR
  hosts_icmp=("127.0.0.1" "8.8.8.8")
  hosts_http=("git.uphillsecurity.com" "uphillsecurity.com" "mettwork.com")
  hosts_tcp=("google.com:443" "uphillsecurity.com:22") # PORT REQUIRED

  # CHECKS
  for h in "${hosts_icmp[@]}"; do
    check_with_retries ICMP "$h" \
      bash -c 'ping -c 1 -W 1 "$1" >/dev/null 2>&1' _ "$h"
  done

  for h in "${hosts_http[@]}"; do
    check_with_retries HTTP "$h" \
      curl -s -o /dev/null --connect-timeout 1 --max-time 2 -f "https://$h"
  done

  for h in "${hosts_tcp[@]}"; do
    check_with_retries TCP "$h" \
      bash -c 'nc -z -w 1 "$1" "$2" >/dev/null 2>&1' _ ${h%:*} ${h##*:}
  done
}

main