import crypto from 'crypto';
import fs from 'fs/promises';
import path from 'path';

export function getAttachmentsDir(): string {
  return process.env.ATTACHMENTS_DIR || path.join(process.cwd(), 'data', 'attachments');
}

export async function saveAttachmentBuffer(
  buffer: Buffer,
  originalFilename: string,
  mimeType: string
): Promise<{
  md5Hash: string;
  storagePath: string;
  sizeBytes: number;
  extractedText: string | null;
}> {
  const md5Hash = crypto.createHash('md5').update(buffer).digest('hex');
  const ext = path.extname(originalFilename) || guessExtensionFromMime(mimeType);
  const subDir = md5Hash.slice(0, 2);
  const baseDir = getAttachmentsDir();
  const targetDir = path.join(baseDir, subDir);
  await fs.mkdir(targetDir, { recursive: true });

  const fileNameOnDisk = `${md5Hash}${ext}`;
  const fullPath = path.join(targetDir, fileNameOnDisk);

  try {
    await fs.access(fullPath);
  } catch {
    await fs.writeFile(fullPath, buffer);
  }

  let extractedText: string | null = null;
  if (
    mimeType.startsWith('text/') ||
    mimeType === 'application/json' ||
    mimeType === 'application/xml' ||
    originalFilename.endsWith('.md') ||
    originalFilename.endsWith('.txt') ||
    originalFilename.endsWith('.csv')
  ) {
    extractedText = buffer.toString('utf-8').slice(0, 50000);
  }

  return {
    md5Hash,
    storagePath: path.join(subDir, fileNameOnDisk),
    sizeBytes: buffer.length,
    extractedText,
  };
}

export function getFullAttachmentPath(storagePath: string): string {
  const baseDir = getAttachmentsDir();
  const normalizedStoragePath = storagePath.replace(/\\/g, '/');
  const resolved = path.resolve(baseDir, normalizedStoragePath);
  if (!resolved.startsWith(path.resolve(baseDir))) {
    throw new Error('Invalid storage path');
  }
  return resolved;
}

export function guessExtensionFromMime(mime: string): string {
  const map: Record<string, string> = {
    'image/jpeg': '.jpg',
    'image/jpg': '.jpg',
    'image/png': '.png',
    'image/gif': '.gif',
    'image/webp': '.webp',
    'image/svg+xml': '.svg',
    'application/pdf': '.pdf',
    'audio/mpeg': '.mp3',
    'audio/mp3': '.mp3',
    'audio/wav': '.wav',
    'audio/ogg': '.ogg',
    'audio/webm': '.webm',
    'audio/mp4': '.m4a',
    'video/mp4': '.mp4',
    'text/plain': '.txt',
    'text/html': '.html',
    'text/markdown': '.md',
  };
  return map[mime.toLowerCase()] || '.bin';
}

export function stripHtmlToText(html: string): string {
  if (!html) return '';
  return html
    .replace(/<style[^>]*>[\s\S]*?<\/style>/gi, ' ')
    .replace(/<script[^>]*>[\s\S]*?<\/script>/gi, ' ')
    .replace(/<[^>]+>/g, ' ')
    .replace(/&nbsp;/gi, ' ')
    .replace(/&amp;/gi, '&')
    .replace(/&lt;/gi, '<')
    .replace(/&gt;/gi, '>')
    .replace(/&quot;/gi, '"')
    .replace(/&#39;/gi, "'")
    .replace(/\s+/g, ' ')
    .trim();
}

export function makeExcerpt(text: string, maxLen = 220): string {
  if (!text) return '';
  const clean = text.replace(/\s+/g, ' ').trim();
  return clean.length > maxLen ? clean.slice(0, maxLen) + '…' : clean;
}