Function getOpenGraphData

helpers.go:200–256

(ctx context.Context, urlStr string, userID string)

	if err != nil {
		return nil, "", err
	}
	if int64(len(data)) > limit {
		return nil, "", fmt.Errorf("response exceeds allowed size (%d bytes)", limit)
	}

	contentType := resp.Header.Get("Content-Type")
	if contentType == "" {
		contentType = http.DetectContentType(data)
	}

	return data, contentType, nil
}

func getOpenGraphData(ctx context.Context, urlStr string, userID string) openGraphResult {
	// Check cache first
	if cachedData, found := openGraphCache.Get(urlStr); found {
		if data, ok := cachedData.(openGraphResult); ok {
			log.Debug().Str("url", urlStr).Msg("Open Graph data fetched from cache")
			return data
		}
	}

	v, err, _ := openGraphGroup.Do(urlStr, func() (res any, err error) {
		ctx, cancel := context.WithTimeout(ctx, openGraphFetchTimeout)
		defer cancel()

		// Acquire a token from the semaphore pool
		userPool := userSemaphoreManager.ForUser(userID)
		select {
		case userPool <- struct{}{}:
			defer func() { <-userPool }()
		case <-ctx.Done():
			log.Warn().Str("url", urlStr).Msg("Open Graph data fetch timed out while waiting for a worker")
			return nil, ctx.Err()
		}

		// Recover from panics and convert to error
		defer func() {
			if r := recover(); r != nil {
				stack := debug.Stack()
				log.Error().
					Interface("panic_info", r).
					Str("url", urlStr).
					Bytes("stack", stack).
					Msg("Panic recovered while fetching Open Graph data")
				err = fmt.Errorf("panic: %v", r)
			}
		}()

		// Fetch Open Graph data
		result := fetchOpenGraphData(ctx, urlStr)

		// Store in cache
		openGraphCache.Set(urlStr, result, cache.DefaultExpiration)

		return result, nil
	})