import express from 'express';
import cors from 'cors';
import { tmpdir } from 'os';
import { join } from 'path';
import { promises as fs } from 'fs';
import { v4 as uuidV4 } from 'uuid';
import Epub from 'epub-gen';

const app = express();
const PORT = process.env.PORT || 4000;
const ORIGIN = process.env.CLIENT_ORIGIN || 'http://localhost:5173';

app.use(cors({ origin: ORIGIN, credentials: true }));
app.use(express.json({ limit: '10mb' }));

const sanitizeHtml = (text = '') =>
  text
    .replace(/&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#39;')
    .replace(/\n/g, '<br/>');

app.post('/generate-epub', async (req, res) => {
  const { text, meta, cover } = req.body || {};
  if (!text || !text.trim()) {
    return res.status(400).json({ message: 'text is required' });
  }

  const title = meta?.title || 'imgPub OCR Export';
  const author = meta?.author || 'imgPub';
  const filename = meta?.filename || `imgpub${Date.now()}.epub`;

  const content = [
    {
      title,
      data: `<div>${sanitizeHtml(text)}</div>`,
    },
  ];

  const outputPath = join(tmpdir(), `imgpub-${uuidV4()}.epub`);
  let coverPath;

  try {
    if (cover?.data) {
      const coverBuffer = Buffer.from(cover.data, 'base64');
      const coverExtension =
        cover?.mimeType?.split('/').pop() || cover?.filename?.split('.').pop() || 'png';
      coverPath = join(tmpdir(), `imgpub-cover-${uuidV4()}.${coverExtension}`);
      await fs.writeFile(coverPath, coverBuffer);
    }

    const epubOptions = { title, author, content };
    if (coverPath) {
      epubOptions.cover = coverPath;
    }

    const epub = new Epub(epubOptions, outputPath);
    await epub.promise;
    const buffer = await fs.readFile(outputPath);
    await fs.unlink(outputPath).catch(() => {});
    if (coverPath) {
      await fs.unlink(coverPath).catch(() => {});
    }
    res.json({ filename, data: buffer.toString('base64') });
  } catch (error) {
    console.error('EPUB generation failed:', error);
    res.status(500).json({ message: 'EPUB generation failed' });
  }
});

app.get('/', (_, res) => {
  res.json({ status: 'ok' });
});

app.listen(PORT, () => {
  console.log(`imgPub EPUB server listening on port ${PORT}`);
});