embark/lib/modules/blockchain_process/proxy.js

const httpProxy = require('http-proxy');
const http = require('http');
const constants = require('../../constants.json');
const utils = require('../../utils/utils');

let commList = {};
let transactions = {};
let receipts = {};

const {canonicalHost, defaultHost} = require('../../utils/host');

const parseRequest = function (reqBody) {
  let jsonO;
  try {
    jsonO = JSON.parse(reqBody);
  } catch (e) {
    return; // Request is not a json. Do nothing
  }
  if (jsonO.method === "eth_sendTransaction") {
    commList[jsonO.id] = {
      type: 'contract-log',
      address: jsonO.params[0].to,
      data: jsonO.params[0].data
    };
  } else if (jsonO.method === "eth_getTransactionReceipt") {
    if (transactions[jsonO.params[0]]) {
      transactions[jsonO.params[0]].receiptId = jsonO.id;
      receipts[jsonO.id] = transactions[jsonO.params[0]].commListId;
    }
  }
};

const parseResponse = function (ipc, resBody) {
  let jsonO;
  try {
    jsonO = JSON.parse(resBody);
  } catch (e) {
    return; // Response is not a json. Do nothing
  }
  if (commList[jsonO.id]) {
    commList[jsonO.id].transactionHash = jsonO.result;
    transactions[jsonO.result] = {commListId: jsonO.id};
  } else if (receipts[jsonO.id] && jsonO.result && jsonO.result.blockNumber) {
    // TODO find out why commList[receipts[jsonO.id]] is sometimes not defined
    if (!commList[receipts[jsonO.id]]) {
      commList[receipts[jsonO.id]] = {};
    }
    commList[receipts[jsonO.id]].blockNumber = jsonO.result.blockNumber;
    commList[receipts[jsonO.id]].gasUsed = jsonO.result.gasUsed;
    commList[receipts[jsonO.id]].status = jsonO.result.status;

    if (ipc.connected && !ipc.connecting) {
      ipc.request('log', commList[receipts[jsonO.id]]);
    } else {
      ipc.connecting = true;
      ipc.connect(() => {
        ipc.connecting = false;
      });
    }

    delete transactions[commList[receipts[jsonO.id]].transactionHash];
    delete commList[receipts[jsonO.id]];
    delete receipts[jsonO.id];
  }
};

exports.serve = async function (ipc, host, port, ws, origin) {
  const _origin = origin ? origin.split(',')[0] : undefined;
  const start = Date.now();

  function awaitTarget() {
    return new Promise(resolve => {
      utils.pingEndpoint(
        canonicalHost(host), port, ws ? 'ws': false, 'http', _origin, async (err) => {
          if (!err || (Date.now() - start > 10000)) {
            return resolve();
          }
          await utils.timer(250).then(awaitTarget).then(resolve);
        }
      );
    });
  }

  await awaitTarget();

  let proxy = httpProxy.createProxyServer({
    target: {
      host: canonicalHost(host),
      port: port
    },
    ws: ws
  });

  proxy.on('error', function (e) {
    console.error(__("Error forwarding requests to blockchain/simulator"), e.message);
  });

  proxy.on('proxyRes', (proxyRes) => {
    let resBody = [];
    proxyRes.on('data', (b) => resBody.push(b));
    proxyRes.on('end', function () {
      resBody = Buffer.concat(resBody).toString();
      if (resBody) {
        parseResponse(ipc, resBody);
      }
    });
  });

  let server = http.createServer((req, res) => {
    let reqBody = [];
    req.on('data', (b) => {
      reqBody.push(b);
    })
      .on('end', () => {
        reqBody = Buffer.concat(reqBody).toString();
        if (reqBody) {
          parseRequest(reqBody);
        }
      });

    if (!ws) {
      proxy.web(req, res);
    }
  });

  if (ws) {
    const WsParser = require('simples/lib/parsers/ws'); // npm install simples

    server.on('upgrade', function (req, socket, head) {
      proxy.ws(req, socket, head);
    });

    proxy.on('open', (proxySocket) => {
      proxySocket.on('data', (data) => {
        parseResponse(ipc, data.toString().substr(data.indexOf("{")));
      });
    });

    proxy.on('proxyReqWs', (proxyReq, req, socket) => {
      var parser = new WsParser(0, false);
      socket.pipe(parser);
      parser.on('frame', function (frame) {
        parseRequest(frame.data);
      });

    });
  }
  const listenPort = port - constants.blockchain.servicePortOnProxy;
  return new Promise(resolve => {
    server.listen(listenPort, defaultHost, () => {
      resolve(server);
    });
  });
};