/**
 * Normalize asset URL for display.
 * This is the SINGLE source of truth for building static asset URLs.
 * 
 * Handles various URL formats from the backend:
 * - /api/static/uploads/... - already correct, return as-is
 * - /assets/... - static assets in public folder, return as-is
 * - /static/uploads/... - needs /api prefix
 * - https://... or http://... - external URL, return as-is
 * - uploads/... or static/uploads/... - relative path, needs /api/static prefix
 * 
 * IMPORTANT: Do NOT manually concatenate /api/static anywhere in the codebase.
 * Always use this function instead.
 */
export function normalizeAssetUrl(url: string | null | undefined): string | null {
  if (!url) return null;
  
  // External URLs - return as-is
  if (url.startsWith('http://') || url.startsWith('https://')) {
    return url;
  }
  
  // Already correct format with /api/static
  if (url.startsWith('/api/static')) {
    return url;
  }
  
  // Static assets in public folder (/assets/...)
  if (url.startsWith('/assets/')) {
    return url;
  }
  
  // Old format with /static/ prefix - add /api
  if (url.startsWith('/static/')) {
    return `/api${url}`;
  }
  
  // Relative path without leading slash (uploads/..., static/...)
  // Remove any duplicate prefixes and normalize
  let cleaned = url;
  
  // Remove leading /api/static if somehow duplicated
  cleaned = cleaned.replace(/^\/api\/static\//, '');
  // Remove leading /static/
  cleaned = cleaned.replace(/^\/static\//, '');
  // Remove leading static/ (no slash)
  cleaned = cleaned.replace(/^static\//, '');
  // Remove leading slash
  cleaned = cleaned.replace(/^\/+/, '');
  
  // If it looks like a relative upload path, prefix with /api/static/
  if (cleaned.startsWith('uploads/') || cleaned.includes('/')) {
    return `/api/static/${cleaned}`;
  }
  
  // Unknown format - return as-is (might be a simple filename)
  return url;
}