#!/usr/bin/env bash
#
# health-check.sh
# Polls the deployed app's /health and /metrics endpoints every 30 seconds,
# logs status + response time, and writes a rolling JSON snapshot that
# dashboard.html polls to render live status.
#
# Usage:
#   ./health-check.sh https://myapp.ghaymah.systems
#
set -euo pipefail

APP_URL="${1:-https://myapp.ghaymah.systems}"
INTERVAL_SECONDS=30
LOG_FILE="./health-check.log"
STATE_FILE="./status.json"          # consumed by dashboard.html
MAX_HISTORY=100                     # keep last N checks in status.json
ALERT_WEBHOOK="${ALERT_WEBHOOK_URL:-}"   # optional: Slack/Telegram webhook for alerting

FAIL_STREAK=0
FAIL_THRESHOLD=3   # alert after 3 consecutive failures (90s of downtime)

log() {
  echo "$(date -u '+%Y-%m-%dT%H:%M:%SZ') $*" | tee -a "$LOG_FILE"
}

send_alert() {
  local message="$1"
  log "ALERT: ${message}"
  if [[ -n "$ALERT_WEBHOOK" ]]; then
    curl -s -X POST -H 'Content-Type: application/json' \
      -d "{\"text\": \"🚨 ${message}\"}" "$ALERT_WEBHOOK" >/dev/null || true
  fi
}

init_state_file() {
  [[ -f "$STATE_FILE" ]] || echo '{"history": []}' > "$STATE_FILE"
}

append_result() {
  local timestamp="$1" status_code="$2" latency_ms="$3" request_count="$4" healthy="$5"

  local tmp
  tmp=$(mktemp)
  python3 - "$STATE_FILE" "$timestamp" "$status_code" "$latency_ms" "$request_count" "$healthy" "$MAX_HISTORY" <<'PYEOF' > "$tmp"
import json, sys

state_file, ts, code, latency, req_count, healthy, max_hist = sys.argv[1:8]
try:
    with open(state_file) as f:
        data = json.load(f)
except (FileNotFoundError, json.JSONDecodeError):
    data = {"history": []}

data["history"].append({
    "timestamp": ts,
    "status_code": int(code),
    "latency_ms": float(latency),
    "request_count": int(req_count) if req_count.isdigit() else None,
    "healthy": healthy == "1",
})
data["history"] = data["history"][-int(max_hist):]
data["last_check"] = data["history"][-1]
print(json.dumps(data, ensure_ascii=False))
PYEOF
  mv "$tmp" "$STATE_FILE"
}

log "Starting monitor for ${APP_URL} (interval=${INTERVAL_SECONDS}s)"
init_state_file

while true; do
  START_MS=$(date +%s%3N)

  # -o /dev/null discards body, -w prints status code, --max-time caps hang time
  HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" --max-time 5 "${APP_URL}/health" || echo "000")

  END_MS=$(date +%s%3N)
  LATENCY_MS=$((END_MS - START_MS))

  REQUEST_COUNT=$(curl -s --max-time 5 "${APP_URL}/metrics" 2>/dev/null \
    | python3 -c "import sys,json; print(json.load(sys.stdin).get('request_count',''))" 2>/dev/null || echo "")

  if [[ "$HTTP_CODE" == "200" ]]; then
    log "OK   status=${HTTP_CODE} latency=${LATENCY_MS}ms requests=${REQUEST_COUNT}"
    FAIL_STREAK=0
    append_result "$(date -u '+%Y-%m-%dT%H:%M:%SZ')" "$HTTP_CODE" "$LATENCY_MS" "${REQUEST_COUNT:-0}" 1
  else
    FAIL_STREAK=$((FAIL_STREAK + 1))
    log "FAIL status=${HTTP_CODE} latency=${LATENCY_MS}ms fail_streak=${FAIL_STREAK}"
    append_result "$(date -u '+%Y-%m-%dT%H:%M:%SZ')" "$HTTP_CODE" "$LATENCY_MS" "${REQUEST_COUNT:-0}" 0

    if (( FAIL_STREAK >= FAIL_THRESHOLD )); then
      send_alert "${APP_URL} has failed ${FAIL_STREAK} consecutive health checks (last status=${HTTP_CODE})"
    fi
  fi

  sleep "$INTERVAL_SECONDS"
done