const http = require('http');
const crypto = require('crypto');

const secret = process.env.EHI_HMAC_SECRET;
const port = Number(process.env.PORT || 8085);

function sha256Hex(buffer) {
  return crypto.createHash('sha256').update(buffer).digest('hex');
}

http
  .createServer((req, res) => {
    const chunks = [];
    const receivedAt = new Date().toISOString();

    req.on('data', (chunk) => chunks.push(chunk));

    req.on('end', () => {
      const rawBodyBuffer = Buffer.concat(chunks);
      const rawBody = rawBodyBuffer.toString('utf8');

      const signatureTimestamp = req.headers['x-ehi-signature-timestamp'];
      const receivedSignature = req.headers['x-ehi-signature'];
      const algorithm = req.headers['x-ehi-signature-algorithm'];

      const payloadToSignBuffer = Buffer.concat([
        Buffer.from(`${signatureTimestamp}.`, 'utf8'),
        rawBodyBuffer,
      ]);

      const expectedSignature = crypto
        .createHmac('sha256', secret)
        .update(payloadToSignBuffer)
        .digest('hex');

      const report = {
        receivedAt,
        request: {
          method: req.method,
          url: req.url,
          httpVersion: req.httpVersion,
          remoteAddress: req.socket.remoteAddress,
          remotePort: req.socket.remotePort,
          headers: req.headers,
          rawHeaders: req.rawHeaders,
        },
        body: {
          rawBody,
          byteLength: rawBodyBuffer.length,
          sha256: sha256Hex(rawBodyBuffer),
          base64: rawBodyBuffer.toString('base64'),
        },
        hmac: {
          algorithm,
          timestamp: signatureTimestamp,
          receivedSignature,
          expectedSignature,
          matches: receivedSignature === expectedSignature,
          payloadToSignByteLength: payloadToSignBuffer.length,
          payloadToSignSha256: sha256Hex(payloadToSignBuffer),
          secretByteLength: Buffer.byteLength(secret || '', 'utf8'),
          secretFingerprintSha256: sha256Hex(
            Buffer.from(secret || '', 'utf8'),
          ).slice(0, 16),
        },
      };

      console.log('\n================ EHI REQUEST ================');
      console.dir(report, { depth: null, colors: true });
      console.log('=============================================\n');

      res.writeHead(report.hmac.matches ? 200 : 401, {
        'content-type': 'application/json',
      });

      res.end(
        JSON.stringify({
          Acknowledgement: '1',
          Responsestatus: '00',
        }),
      );
    });
  })
  .listen(port, '127.0.0.1', () => {
    console.log(`Mock sponsor on http://127.0.0.1:${port}/ehi`);
  });