/**
 * Datei-URLs für SvelteKit: /cms-files mit persistentem Server-Disk-Cache.
 * Analog zu rusty-image.ts, aber für generische Dateien (PDF, DOCX, ...).
 */

export interface CmsFileField {
  url: string;
  title?: string;
  description?: string;
  size?: number;
  mime?: string;
  filename?: string;
}

/**
 * Extrahiert URL/Title/Description aus einem CMS-File-Field
 * (string oder { src, title?, description?, mime?, size?, ... }).
 */
export function extractCmsFileField(field: unknown): CmsFileField | null {
  if (typeof field === 'string') {
    const s = field.trim();
    if (!s) return null;
    return { url: s.startsWith('//') ? `https:${s}` : s };
  }
  if (field && typeof field === 'object') {
    const o = field as {
      src?: string;
      file?: { url?: string };
      title?: string;
      description?: string;
      size?: number;
      mime?: string;
      filename?: string;
    };
    const rawUrl =
      typeof o.src === 'string' && o.src.trim()
        ? o.src
        : typeof o.file?.url === 'string' && o.file.url.trim()
          ? o.file.url
          : undefined;
    if (!rawUrl) return null;
    const url = rawUrl.startsWith('//') ? `https:${rawUrl}` : rawUrl;
    return {
      url,
      ...(o.title ? { title: o.title } : {}),
      ...(o.description ? { description: o.description } : {}),
      ...(typeof o.size === 'number' ? { size: o.size } : {}),
      ...(o.mime ? { mime: o.mime } : {}),
      ...(o.filename ? { filename: o.filename } : {}),
    };
  }
  return null;
}

export interface CmsFileUrlOptions {
  /** Filename hint for Content-Disposition header. */
  filename?: string;
  /** Force download (Content-Disposition: attachment). */
  download?: boolean;
}

/**
 * Lokale Datei-URL: /cms-files?src=…&name=…&dl=…
 * `src` = volle Datei-URL oder CMS-Asset-Pfad (`/api/assets/...`).
 */
export function getCmsFileUrl(src: string, opts: CmsFileUrlOptions = {}): string {
  const params = new URLSearchParams();
  params.set('src', src);
  if (opts.filename) params.set('name', opts.filename);
  if (opts.download) params.set('dl', '1');
  return `/cms-files?${params.toString()}`;
}

const SIZE_UNITS = ['B', 'KB', 'MB', 'GB'];

export function formatFileSize(bytes?: number): string | null {
  if (typeof bytes !== 'number' || !Number.isFinite(bytes) || bytes <= 0) return null;
  let b = bytes;
  let i = 0;
  while (b >= 1024 && i < SIZE_UNITS.length - 1) {
    b /= 1024;
    i++;
  }
  const rounded = b >= 10 || i === 0 ? Math.round(b) : Math.round(b * 10) / 10;
  return `${rounded} ${SIZE_UNITS[i]}`;
}

export function fileExtFromUrl(url: string): string | null {
  try {
    const path = url.split('?')[0].split('#')[0];
    const last = path.split('/').pop() ?? '';
    const dot = last.lastIndexOf('.');
    return dot >= 0 ? last.slice(dot + 1).toLowerCase() : null;
  } catch {
    return null;
  }
}