/**
 * Persistenter Disk-Cache für CMS-Dateien (PDF, DOCX, ...).
 * Analog zu image-cache.server.ts: Datei einmal vom CMS holen, auf Disk
 * speichern, danach direkt von dort ausliefern.
 */

import { createHash } from 'node:crypto';
import { existsSync, mkdirSync } from 'node:fs';
import { readFile, readdir, writeFile } from 'node:fs/promises';
import { extname, join } from 'node:path';
import { env } from '$env/dynamic/private';

const CACHE_DIR = env.FILE_CACHE_DIR?.trim() || '.cache/files';
const MAX_MEMORY_ENTRIES = Number(env.FILE_CACHE_MAX_MEMORY) || 50;

export interface CachedFile {
  buffer: Buffer;
  contentType: string;
  ext: string;
}

const memoryCache = new Map<string, CachedFile>();
let resolvedDir: string | null = null;

function ensureCacheDir(): string {
  const dir = resolvedDir ?? join(process.cwd(), CACHE_DIR);
  if (!existsSync(dir)) mkdirSync(dir, { recursive: true });
  resolvedDir = dir;
  return dir;
}

export function buildFileCacheKey(src: string): string {
  return createHash('sha256').update(src).digest('hex').slice(0, 24);
}

const EXT_TO_CT: Record<string, string> = {
  pdf: 'application/pdf',
  doc: 'application/msword',
  docx: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
  xls: 'application/vnd.ms-excel',
  xlsx: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
  ppt: 'application/vnd.ms-powerpoint',
  pptx: 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
  odt: 'application/vnd.oasis.opendocument.text',
  ods: 'application/vnd.oasis.opendocument.spreadsheet',
  zip: 'application/zip',
  txt: 'text/plain; charset=utf-8',
  csv: 'text/csv; charset=utf-8',
  json: 'application/json',
  xml: 'application/xml',
  rtf: 'application/rtf',
  jpg: 'image/jpeg',
  jpeg: 'image/jpeg',
  png: 'image/png',
  webp: 'image/webp',
  gif: 'image/gif',
  svg: 'image/svg+xml',
};

export function contentTypeFromExt(ext: string): string {
  return EXT_TO_CT[ext.toLowerCase()] ?? 'application/octet-stream';
}

export function extFromContentType(ct: string): string | null {
  const lower = ct.toLowerCase();
  for (const [ext, mime] of Object.entries(EXT_TO_CT)) {
    if (lower.startsWith(mime.split(';')[0])) return ext;
  }
  return null;
}

export function extFromSrc(src: string): string | null {
  try {
    const path = src.split('?')[0].split('#')[0];
    const e = extname(path).slice(1).toLowerCase();
    return e || null;
  } catch {
    return null;
  }
}

function rememberInMemory(key: string, cached: CachedFile): CachedFile {
  if (memoryCache.size >= MAX_MEMORY_ENTRIES) {
    const oldest = memoryCache.keys().next().value;
    if (oldest !== undefined) memoryCache.delete(oldest);
  }
  memoryCache.set(key, cached);
  return cached;
}

export async function getCachedFile(key: string): Promise<CachedFile | null> {
  const mem = memoryCache.get(key);
  if (mem) return mem;

  const dir = ensureCacheDir();
  try {
    const files = await readdir(dir);
    const prefix = `${key}.`;
    const name = files.find((f) => f.startsWith(prefix));
    if (!name) return null;
    const buf = await readFile(join(dir, name));
    const ext = name.slice(prefix.length);
    return rememberInMemory(key, {
      buffer: buf,
      contentType: contentTypeFromExt(ext),
      ext,
    });
  } catch {
    return null;
  }
}

export async function cacheFile(
  key: string,
  buffer: ArrayBuffer | Buffer,
  contentType: string,
  srcHint?: string,
): Promise<CachedFile> {
  const dir = ensureCacheDir();
  const buf = Buffer.isBuffer(buffer) ? buffer : Buffer.from(buffer);
  const ext =
    extFromContentType(contentType) ??
    (srcHint ? extFromSrc(srcHint) : null) ??
    'bin';
  const cached: CachedFile = { buffer: buf, contentType, ext };
  rememberInMemory(key, cached);
  await writeFile(join(dir, `${key}.${ext}`), buf);
  return cached;
}