Get a Random Value from API

This section showcases how to get a random value inside a smart contract using Oraichain VRF 2.0

Prerequisite

Before integrating Oraichain VRF 2.0 into your tech stack, you need to install Oraichain cosmosjs library. Kindly follow the steps as demonstrated here.

Integration steps

For Back-end Usage

Step 1: Import Oraichain cosmosjs library

const Cosmos = require("@oraichain/cosmosjs").default;

const lcdUrl = "https://lcd.orai.io";
const chainId = "Oraichain";
const mnemonic = "foo bar";
const requestFees = “100”;

const message = Cosmos.message;
const cosmos = new Cosmos(lcdUrl, chainId);
const childKey = cosmos.getChildKey(mnemonic);
const sender = cosmos.getAddress(mnemonic);

cosmos.setBech32MainPrefix('orai');

Step 2: Request a random transaction

const input = Buffer.from(
       JSON.stringify({
           request_random: {
               input: btoa(userInput),
           },
       })
   );
 
const txBody = getHandleMessage(contract, input, sender, requestFees);
const response = await cosmos.submit(childKey, txBody, "BROADCAST_MODE_BLOCK", isNaN(fees) ? 0 : parseInt(fees), gas);

Enter a string value of your preference at userInput. You will see the fee for your request at requestFees. Also, maximum gas and tx fee need to be decided before each request.

⚠️ In the unlikely case that your request takes too long to respond, try switching "BROADCAST_MODE_BLOCK" to "BROADCAST_MODE_SYNC", and use tx hash to query until it is included on-chain.

Regarding how to query tx hash, please refer to this example or this.

Step 3: Get a random round number

const round = response.tx_response.logs[0].events[1].attributes[3].value;

Step 4: Get the information from a round

const queryRoundInput = JSON.stringify({
       get_round: {round: parseInt(round)},
   });
 
   const roundOutput = await cosmos.get(`/wasm/v1beta1/contract
/${contract}/smart/${Buffer.from(queryRoundInput).toString("base64")}`);

contract is the contract address of the VRF issued by Oraichain and can be reviewed on Oraiscan any time**.**

If the round result has not displayed the randomness output, you just need to wait for some time before querying again.

For browser usage

Step 1: Import Oraichain cosmosjs library

import Cosmos from "@oraichain/cosmosjs";
const lcdUrl = "https://lcd.orai.io";
const chainId = "Oraichain";
const requestFees = “100”;

const message = Cosmos.message;
const cosmos = new Cosmos(lcdUrl, chainId);

Step 2: Import keystation for wallet use by creating a new js file

// @ts-nocheck
/* eslint-disable eqeqeq */
// Find Left Boundry of the Screen/Monitor
function FindLeftScreenBoundry() {
   // Check if the window is off the primary monitor in a positive axis
   // X,Y                  X,Y                    S = Screen, W = Window
   // 0,0  ----------   1280,0  ----------
   //     |          |         |  ---     |
   //     |          |         | | W |    |
   //     |        S |         |  ---   S |
   //      ----------           ----------
   if (window.leftWindowBoundry() > window.screen.width) {
       return window.leftWindowBoundry() - (window.leftWindowBoundry() - window.screen.width);
   }
 
   // Check if the window is off the primary monitor in a negative axis
   // X,Y                  X,Y                    S = Screen, W = Window
   // 0,0  ----------  -1280,0  ----------
   //     |          |         |  ---     |
   //     |          |         | | W |    |
   //     |        S |         |  ---   S |
   //      ----------           ----------
   // This only works in Firefox at the moment due to a bug in Internet Explorer opening new windows into a negative axis
   // However, you can move opened windows into a negative axis as a workaround
   if (window.leftWindowBoundry() < 0 && window.leftWindowBoundry() > window.screen.width * -1) {
       return window.screen.width * -1;
   }
 
   // If neither of the above, the monitor is on the primary monitor whose's screen X should be 0
   return 0;
}
 
window.leftScreenBoundry = FindLeftScreenBoundry;
 
function PopupCenter(url, title, w, h) {
   const newWindow = window.open(
       url,
       title,
       "resizable=1, scrollbars=1, fullscreen=0, height=" +
       h +
       ", width=" +
       w +
       ", screenX=" +
       window.leftScreenBoundry +
       " , left=" +
       window.leftScreenBoundry +
       ", toolbar=0, menubar=0, status=1"
   );
   return newWindow;
}
 
function openWindowV1(type, payload, account = "", self) {
   console.log(`open ${self.client}`);
 
   // The account parameter is required for users having multiple keychain accounts.
   let apiUrl = "";
   switch (type) {
       case "signin":
           apiUrl = "signin";
           break;
       case "transaction":
           apiUrl = "tx";
           break;
       default:
           apiUrl = "signin";
           break;
   }
 
   return PopupCenter(
       self.keystationUrl +
       "/" +
       apiUrl +
       "?account=" +
       encodeURIComponent(account) +
       "&client=" +
       encodeURIComponent(self.client) +
       "&lcd=" +
       encodeURIComponent(self.lcd) +
       "&path=" +
       encodeURIComponent(self.path) +
       "&payload=" +
       encodeURIComponent(JSON.stringify(payload)),
       "",
       "470",
       "760"
   );
}
 
function openWindowV2(type, payload, account = "", self) {
   console.log(`open ${self.client}`);
 
   // The account parameter is required for users having multiple keychain accounts.
   let apiUrl = "";
   switch (type) {
       case "signin":
           apiUrl = "signin";
           break;
       case "transaction":
           apiUrl = "transaction";
           break;
       case "ai-request":
           apiUrl = "ai_request/set";
           break;
       default:
           apiUrl = "auth";
           break;
   }
 
   const network = "Oraichain";
   return PopupCenter(
       self.keystationUrl +
       "/" +
       apiUrl +
       "?lcd=" +
       encodeURIComponent(self.lcd) +
       "&raw_message=" +
       encodeURIComponent(JSON.stringify(payload)) +
       "&signInFromScan=true" +
       "&network=" +
       network,
       "",
       "470",
       "760"
   );
}
 
export default class Keystation {
   constructor(params) {
       if (!params) {
           return;
       }
       const { client, lcd, path, keystationUrl } = params;
       this.client = client;
       this.lcd = lcd;
       this.path = path;
 
       this.keystationUrl = keystationUrl;
   }
 
   openWindow(type, payload, account = "") {
       const self = this;
       return process.env.REACT_APP_WALLET_VERSION == 2 ? openWindowV2(type, payload, account, self) : openWindowV1(type, payload, account, self);
   }
}
 
export const myKeystation = new Keystation({
   client: "https://api.wallet.orai.io",
   lcd: "https://lcd.orai.io",
   path: "44/118/0/0/0",
   keystationUrl: "https://api.wallet.orai.io",
});

Step 3: Create a randomness request

const input = Buffer.from(
       JSON.stringify({
           request_random: {
               input: btoa(userInput),
           },
       })
   );
 
const {privateKey, chainCode, network} = await getChildKey();
const childKey = fromPrivateKey(Buffer.from(privateKey), Buffer.from(chainCode), network);
 
const sender = cosmos.getAddress(childKey);
 
 
const txBody = getHandleMessage(contract, input, sender, requestFees);
const response = await cosmos.submit(childKey, txBody, "BROADCAST_MODE_BLOCK", isNaN(fees) ? 0 : parseInt(fees), gas);

Function getChildKey() is as follow:

   // const popup = window.open(`${config.walletapi}/auth?signInFromScan=true`, "", "resizable=1, scrollbars=1, fullscreen=0, width=470, height=760");
   const popup = myKeystation.openWindow("auth", "");
 
   return new Promise((resolve, reject) => {
       const loop = setInterval(function() {
           if (!popup) {
               clearInterval(loop);
               reject("window-blocked");
           } else if (popup.closed) {
               clearInterval(loop);
               reject("window-closed");
           }
       }, 500);
       const handler = e => {
           if (e.data.privateKey && e.data.chainCode && e.data.network) {
               clearInterval(loop);
               window.removeEventListener("message", handler);
               resolve(e.data);
           }
       };
       window.addEventListener("message", handler);
   });
};

Step 4: Repeat the previously mentioned step 3 and 4 to get the random value and round information