import {config} from 'dotenv';
import {ImapFlow} from 'imapflow';
import express from 'express';

config({path: '.env.local'});

const app = express();
const port = process.env.PORT || 4000;

app.use(async (request, response, next) => {
  try {
    const [user, pass] = Buffer.from(request.headers['authorization']!.replace(/^Basic /, ''), 'base64')
      .toString('utf8')
      .split(':');

    const client = new ImapFlow({
      host: 'imap.server.uni-frankfurt.de',
      port: 993,
      secure: true,
      emitLogs: false,
      auth: {user, pass},
    });
    response.locals.client = client;

    await client.connect();
    response.on('finish', async () => {
      await client.logout();
      client.close();
    });

    next();
  } catch {
    response.status(401).send();
  }
});

app.get('/', async (_request, response) => {
  const result = await response.locals.client.listTree();
  response.json(result);
});

app.get('/:mailbox', async (request, response) => {
  try {
    await response.locals.client.mailboxOpen(request.params.mailbox);
    const since = Number(request.query.since) || undefined;
    const preData = await response.locals.client.status(request.params.mailbox, {messages: true});
    if (preData.messages === 0) {
      response.json([]);
      return;
    }

    const data = response.locals.client.fetch(
      '1:*',
      {},
      {
        // caution, BigInt can throw
        changedSince: typeof since === 'string' ? BigInt(since) : undefined,
      },
    );

    const messages = [];
    for await (const message of data) {
      messages.push(message.seq.toString());
    }
    response.json(messages);
  } catch (error) {
    console.error(error);
    response.status(404).send();
  }
});

app.get('/:mailbox/:id', async (request, response) => {
  try {
    await response.locals.client.mailboxOpen(request.params.mailbox);
    const message = await response.locals.client.fetchOne(request.params.id, {
      envelope: true,
      labels: true,
      flags: true,
      bodyStructure: true,
    });
    response.json({
      bodyStructure: message.bodyStructure,
      labels: [...(message.labels ?? [])],
      flags: [...(message.flags ?? [])],
      envelope: message.envelope,
      seq: message.seq,
    });
  } catch (error) {
    console.error(error);
    response.status(404).send();
  }
});

app.get('/:mailbox/:id/:part', async (request, response) => {
  try {
    await response.locals.client.mailboxOpen(request.params.mailbox, {readOnly: true});
    if (request.query.raw) {
      const message = await response.locals.client.fetchOne(request.params.id, {
        bodyParts: [`${request.params.part}.mime`, request.params.part],
      });

      response.write(message.bodyParts.get(`${request.params.part}.mime`));
      response.write(message.bodyParts.get(request.params.part));

      response.end();
    } else {
      const message = await response.locals.client.download(request.params.id, request.params.part);
      message.content.on('data', chunk => {
        response.write(chunk);
      });
      message.content.on('end', () => {
        response.end();
      });
    }
  } catch (error) {
    console.error(error);
    response.status(404).send();
  }
});

app.listen(port, () => {
  console.log(`Server listening on port ${port}`);
});