Introduction

Oracles are devices or entities that connect a blockchain network to the outside world. They enable smart contracts to access all kinds of off-chain information by entering every data input through an external transaction.

Umbrella

Available Price feeds

https://umbrella-network.readme.io/docs/price-feeds

Deployed Smart contracts

https://umbrella-network.readme.io/docs/umb-token-contracts

Example: fetching a price feed

import {Client, Args, IReadData} from "@massalabs/massa-web3";
import keccak256 from "@indeliblelabs/keccak256";
import {getClient} from "./utils";

import {
  Args,
  IDeserializedResult,
  ISerializable,
} from '@massalabs/massa-web3';

export class PriceData implements ISerializable<PriceData> {
  private data: number = 0; // u8
  private heartbeat: number = 0; // u32
  private timestamp: number = 0; // u32
  private price: bigint = BigInt(0); // u128

  constructor(data: number = 0, heartbeat: number = 0, timestamp: number = 0, price: bigint = BigInt(0)) {
    this.data = data;
    this.heartbeat = heartbeat;
    this.timestamp = timestamp;
    this.price = price;
  }

  serialize(): Uint8Array {
    let args = new Args()
        .addU8(this.data)
        .addU32(this.heartbeat)
        .addU32(this.timestamp)
        .addU128(BigInt(this.price));
    return new Uint8Array(args.serialize());
  }
  deserialize(data: Uint8Array, offset: number): IDeserializedResult<PriceData> {
    const args = new Args(data, offset);
    this.data = parseInt(args.nextU8().toString());
    this.heartbeat = args.nextU32();
    this.timestamp = args.nextU32();
    this.price = BigInt(parseInt(args.nextU128().toString()));
    return { instance: this, offset: args.getOffset() };
  }
}

let getPriceDataArgs = new Args();
let pair_ = keccak256("MS-USD");
getPriceDataArgs.addUint8Array(new Uint8Array(pair_));
const scAddr: string = "AS12bVikBj3xFP3ouP71hpWbzLRDTxq2RaY2ssQWzoSZJUdK3aRm";

const {client, account} = await getClient();

let readData: IReadData = {
    maxGas: BigInt(40_000_000),
    targetAddress: scAddr,
    targetFunction: "getPriceData",
    parameter: getPriceDataArgs,
}
const resp = await client.smartContracts().readSmartContract(readData);
const priceData = new Args(resp.returnValue).nextSerializable(PriceData);
console.log("priceData:", priceData);