aelf-bridge

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Descriptions

Table of Contents

• Introduction
• Installation
  • Using version management tools
  • Using the script tag
• Usage
  • Introduction
  • Initialization
    • Options
  • Get wallet account information
  • Call contract method (read-only and send transaction)
  • Calling the chain API
  • disconnect

Introduction

Since dApps are not allowed to store any wallet information, the wallet application stores AElf wallet information and can communicate directly with the AElf chain. In order to protect wallet information and provide dApps with the ability to interact with the chain, aelf-bridge can be used for interacting with the wallet.

The wallet App described here includes a mobile (iOS/Android) native app, desktop app and more.

Installation

AElf-bridge is part of the AElf ecosystem. Since dApps are mostly web applications, we provide a JavaScript SDK available using Npm or yarn as a version management tool or directly with the script tag.

Using version management tools

npm i aelf-bridge
// or
yarn add aelf-bridge

Using the script tag

<script src="https://unpkg.com/aelf-bridge@latest/dist/aelf-bridge.js"></script>

Usage

Introduction

The communications between a dApp and the chain need to go through some wallet software. This wallet software could be any client that has implemented the AElf bridge protocol. at the time of writing (2020.06), AElf mobile wallet App and aelf-command have implemented this protocol.

Since dApps are mostly web applications and web applications can communicate with clients in many ways, this SDK supports two of them:

• postMessage: a dApp will run in a container (iframe or mobile Apps' webview), and the container needs to overwrite window.postMessage method in the dApp, so the dApp and the container can communicate with each other by overwritten postMessage. AElf mobile wallet App has implemented this.
• WebSocket(Socket.io): use traditional B/S architecture, communicate by WebSocket. SDK uses Socket.io to support WebSocket communication, and this requires servers need to support Socket.io too. aelf-command has implemented this way.

Developers can choose one of them depending on requirements, in the process of development, we provide two ways to support data mock and debugging:

• aelf-bridge-demo: this demo uses iframe to overwrite dapp.html's postMessage to simulate communication with mobile Apps.
• aelf-command dapp-server: aelf-command provides a simple socket.io server to support the communication method socket.io in aelf-bridge, developers can change the communication way to SOCKET.IO, and give the URI given by running aelf-command dapp-server as an option when initializing aelf-bridge instance. Therefore, developers can inspect the communications in the Network tab of browser.

Initialization

import AElfBridge from 'aelf-bridge';

// Initialize the bridge instance, you can pass options during initialization to specify the behavior, see below for explanation
const bridgeInstance = new AElfBridge();
// init with options
const bridgeInstance = new AElfBridge({
  timeout: 5000 // ms
});

// After initializing the instance you need connect
bridgeInstance.connect().then(isConnected => {
  // isConnected True if the connection was successful.
})

Options

The options can be passed as follows:

const defaultOptions = {
  proxyType: String, // The default is `POST_MESSAGE`. Currently, we support the `POST_MESSAGE` and `SOCKET.IO` proxy types are provided. The `Websocket` mechanism will be provided in the future. Valid values ​​are available via `AElfBridge.getProxies()`.
  channelType: String, // The default is `SIGN`, it is the serialization of the request and response, that is, Dapp exchanges the public and private keys with the client and the private key is used to verify the signature information, thereby verifying whether the information has been tampered with. Another method of symmetric encryption is provided. The parameter value is `ENCRYPT`, and the shared public key is used for symmetric encryption. The valid value of the parameter is obtained by `AElfBridge.getChannels()`.
  timeout: Number, // Request timeout, defaults to 3000 milliseconds
  appId: String, // The default is empty. Dapp does not specify if there is no special requirement. If you need to specify it, you need to randomly generate a 32-bit hex-coded id each time. A credential used to communicate with the client, specifying the Dapp ID. If it is not specified, the library will process it internally. The first run will generate a random 32-bit hex-encoded uuid. After the connection is successful, it will be stored in `localStorage`, then the value will be taken from `localStorage`. If not, then Generate a random id.
  endpoint: String, // The default is empty. If the address of the node is empty, the client uses the internally saved primary link address by default, and can also specify to send a request to a specific node.
  // Optional options in `POST_MESSAGE` communication mode
  origin: String, // The default is `*`, the second parameter of the `postMessage` function, in most cases you do not need to specify
  checkoutTimeout: Number, // The default is `200`, in milliseconds, it checks the client's injected `postMessage`. In most cases, you don't need to specify this
  urlPrefix: String, // The default is `aelf://aelf.io?params=`, which is used to specify the protocol and prefix of the node. If the client does not have special requirements, it does not need to be changed.
  // Optional options in `socket.io` communication mode.
  socketUrl: String, // The address of the websocket connection, the default is `http://localhost:50845`
  socketPath: String, // Path to the connection address, the default is empty
  messageType: String // Pass the type of the socket.io message, the default is `bridge`
}

Get wallet account information

bridgeInstance.account()

bridgeInstance.account().then(res => {
  console.log(res);
})
res = {
  "accounts": [
    {
      "name": "test",
      "address": "XxajQQtYxnsgQp92oiSeENao9XkmqbEitDD8CJKfDctvAQmH6"
    }
   ],
  "chains": [
    {
      "url": "http://13.231.179.27:8000",
      "isMainChain": true,
      "chainId": "AELF"
    },
    {
      "url": "http://52.68.97.242:8000",
      "isMainChain": false,
      "chainId": "2112"
    },
    {
      "url": "http://52.196.227.200:8000",
      "isMainChain": false,
      "chainId": "2113"
    }
  ]
}

Calling the chain API

API for interacting with the node. The API available methods can be viewed by {chain address}/swagger/index.html, to get the currently supported APIs you can call AElfBridge.getChainApis().

Developer can use the methods of bridgeInstance.chain to call the api.

Example:

• Get block height

bridgeInstance.chain.getBlockHeight().then(console.log).catch(console.log)

• Get chain status

bridgeInstance.chain.getChainStatus().then(console.log).catch(console.log)

Call contract method (read-only and send transaction)

• Get contract method list
• Send transaction
• Contract read-only method

Example:

• Call the Transfer method of the Token contract to initiate a transfer transaction

const tokenAddress = 'mS8xMLs9SuWdNECkrfQPF8SuRXRuQzitpjzghi3en39C3SRvf'; // Get contract address by genesis contract method `GetContractAddressByName`
bridgeInstance.chain.contractAt(tokenAddress).then(async contract => {
    const tokenInfo = await contract.GetTokenInfo.call({symbol: 'ELF'});
    const transactionId = await contract.Transfer({
          amount: "10000000000",
          to: "fasatqawag",
          symbol: "ELF",
          memo: "transfer ELF"
    });
    console.log(tokenInfo);
    console.log(transactionId);
})

disconnect

Used to disconnect from the client and clearing the public key information, etc.

bridgeInstance.disconnect()