#!/bin/bash
# docker-health-check.sh
# Scans all running containers, reports unhealthy ones,
# and sends a Telegram alert if anything is wrong.
#
# Usage: bash docker-health-check.sh
# Cron:  */5 * * * * /usr/local/bin/docker-health-check.sh
#
# Config: set TELEGRAM_TOKEN and TELEGRAM_CHAT_ID below,
# or export them as environment variables before running.

set -euo pipefail

TELEGRAM_TOKEN="${TELEGRAM_TOKEN:-}"
TELEGRAM_CHAT_ID="${TELEGRAM_CHAT_ID:-}"
ALERT_ON_MISSING_HEALTH="${ALERT_ON_MISSING_HEALTH:-false}"

# ── Collect container status ─────────────────────────────────────
unhealthy=()
missing_health=()

while IFS= read -r name; do
  [[ -z "$name" ]] && continue
  status=$(docker inspect --format '{{if .State.Health}}{{.State.Health.Status}}{{end}}' "$name" 2>/dev/null)

  case "$status" in
    unhealthy)
      unhealthy+=("$name")
      ;;
    "")
      [[ "$ALERT_ON_MISSING_HEALTH" == "true" ]] && missing_health+=("$name")
      ;;
  esac
done < <(docker ps --format '{{.Names}}' 2>/dev/null)

# ── Build message ────────────────────────────────────────────────
issues=0
message=""

if [[ ${#unhealthy[@]} -gt 0 ]]; then
  issues=1
  message+="🔴 *Unhealthy containers:*\n"
  for c in "${unhealthy[@]}"; do
    message+="  • ${c}\n"
    # Grab last 5 log lines for context
    logs=$(docker logs --tail 5 "$c" 2>&1 | tail -5 || true)
    message+="    \`${logs}\`\n"
  done
fi

if [[ ${#missing_health[@]} -gt 0 && "$ALERT_ON_MISSING_HEALTH" == "true" ]]; then
  message+="⚠️ *No healthcheck defined:*\n"
  for c in "${missing_health[@]}"; do
    message+="  • ${c}\n"
  done
fi

# ── Send Telegram alert if issues found ──────────────────────────
if [[ $issues -eq 1 && -n "$TELEGRAM_TOKEN" && -n "$TELEGRAM_CHAT_ID" ]]; then
  curl -s -X POST "https://api.telegram.org/bot${TELEGRAM_TOKEN}/sendMessage" \
    -d "chat_id=${TELEGRAM_CHAT_ID}" \
    -d "parse_mode=Markdown" \
    -d "text=${message}" \
    > /dev/null
fi

# ── Exit code for cron/systemd monitoring ────────────────────────
if [[ $issues -eq 1 ]]; then
  echo "[$(date)] UNHEALTHY: ${unhealthy[*]}"
  exit 1
else
  echo "[$(date)] All containers healthy"
  exit 0
fi