Two-way centralized swap service for ERC20<->ENQ tokens transactions

The service was developed to swap Enecuum tokens from the Ethereum network to native Enecuum network.

Installation

Create database: mysql -p -e "DROP DATABASE IF EXISTS wallet; CREATE DATABASE wallet;"

Create schema: mysql -p wallet < wallet.sql

Install Node.JS packages: npm i

Use config.json.example to get test config for backend.

```
cp config.json.example config.json
```

In config.json set required fields:

• nodeURL is an address of Enecuum Blockchain Explorer

• eth section:

      "RPC" : Ethereum node HTTPS address
      "wsRPC" : Ethereum node Websocket address
      "tokenAddr" : Ethereum token contract address to be swapped
      "cashierGasPriceLimit" : Maximum gas limit for ERC20 TX in ENQ->ERC20 swap
      "minConf" : number of confirmations in ETH network for ERC20->ENQ swap
      "minSwapLimit" : minimal amount for ENQ->ERC20 swap
  

• eth_techAddr : Ethereum technical address, recipient for ERC20->ENQ swaps

• enq_techAddr: Enecuum technical address, recipient for ENQ->ERC20 swaps

• keys object manages keys for outcoming TXs for swaps

• Database parameters

Start

Start PM2 process: pm2 start index.js --name wallet --log-date-format "YYYY-MM-DD HH:mm Z

Usage

The main goal of this service was ENQ token migration from ETH network, so the service supports the following options:

• ERC-20 ENQ token ---> Native ENQ coin
• Native ENQ coin ---> ERC-20 ENQ token

After service start, two swap API routes will be available:

• /swap/erc/enq
• /swap/enq/erc

ERC-20 ---> ENQ

To start ERC-20 -> ENQ (native) you need to send a special Ethereum token transaction with X amount of tokens (excluding fees) to be swapped to eth_techAddr address. It's a basic ERC-20 token contract transaction but with additional info in data field. You need to add Enecuum address (the same as pubkey in POST body below) in data field after all contract-relative data.

The Swap service monitors all incoming Ethereum transactions to the eth_techAddr address. When a transaction of tokenAddr token and eth_techAddr recipient has been detected, the service validate this transaction and also use last 33 bytes of raw TX's data field as Enecuum native coins recipient address - pubkey. After minConf block confirmations it sends Enecuum transaction of X coins (excluding fees) from config.keys.enq.pub address to pubkey Enecuum address obtained at previous step.

NOTE: Because of some issues in web3.js (probably fixed) there are some Websocket connection errors with Ethereum RPC. It may cause a transaction skip. For this case there is an API path:

POST /swap/erc/enq

In this case to perform a (ENQ ERC-20) ---> (ENQ native) swap you need to make POST request to /swap/erc/enq with body:

    {
        pubkey : Enecuum address (on which you want to get native coins) like 037507b65c61bd6a1252f1acc08fece35f9053a6806e847cd712b1eab90529b86e,
        hash : Ethereum transaction hash of token swap transaction,
        eth_addr : Ethereum address of token sender,
        amount : Amount of tokens to be swapped
    }

It is assumed that the ETH transaction with hash hash has already been made.

ENQ ---> ERC-20

To perform (ENQ native) ---> (ENQ ERC-20) swap you need to prepare and sign Enecuum transaction, then make a POST request to /swap/enq/erc with body:

{
    pubkey : Enecuum coin sender address,
    eth_addr : Ethereum addres (on which you want to get ERC-20 tokens),
    tx : { // Enecuum signed transaction object
        amount : "",
        data : "",
        from : "",
        nonce : "",
        ticker : "",
        to : ""
    }
}

The service are relaying tx object to the Enecuum node and starting to check TX status. When it gets status 3, an Ethereum token transaction of tx.amount tokens (excluding fee) from config.keys.eth.pub to eth_addr Ethereum address will be made.