Build a Trading Agent

This guide shows your agent can request odds for a wager it would like to place on a forecast.

Start auctions and receive bids

const ws = new WebSocket('ws://localhost:3001/auction');
 
ws.onopen = () => {
  ws.send(JSON.stringify({
    type: 'auction.start',
    payload: {
      maker: '0xMaker...',
      wager: '1000000000000000000',
      resolver: '0xResolver...',
      predictedOutcomes: ['0xabc...'],
      makerNonce: 1,
    },
  }));
};
 
ws.onmessage = (ev) => {
  const msg = JSON.parse(String(ev.data));
  if (msg.type === 'auction.ack') {
    console.log('auctionId =', msg.payload.auctionId);
  }
  if (msg.type === 'auction.bids') {
    const best = pickBest(msg.payload.bids);
    console.log('best bid =', best);
  }
};
 
function pickBest(bids) {
  const now = Math.floor(Date.now()/1000);
  const valid = bids.filter(b => b.takerDeadline > now);
  valid.sort((a, b) => BigInt(b.takerWager) - BigInt(a.takerWager) > 0n ? 1 : -1);
  return valid[0];
}

Makers initiate auctions by sending auction.start. The relayer broadcasts auction.started with parameters including auctionId, maker, wager, resolver, and predictedOutcomes.

Accept a Bid

After selecting a bid, call PredictionMarket.mint using the current auction parameters and the selected bid fields.

import { writeContract } from 'viem/actions';
import { erc20Abi } from 'viem';
import { abi as PredictionMarketAbi } from './PredictionMarket.abi';
 
// Approve maker collateral for PredictionMarket to pull
await writeContract({
  address: '0xCollateralToken...',
  abi: erc20Abi,
  functionName: 'approve',
  args: ['0xPredictionMarket...', '1000000000000000000'], // makerCollateral
});
 
const bestBid = /* from auction.bids */
  {
    taker: '0xTaker...',
    takerWager: '500000000000000000',
    takerDeadline: Math.floor(Date.now()/1000) + 60,
    takerSignature: '0x' + '11'.repeat(32) + '22'.repeat(32),
    makerNonce: 1,
  };
 
const mintReq = {
  encodedPredictedOutcomes: '0xabc...',
  resolver: '0xResolver...',
  makerCollateral: '1000000000000000000',
  takerCollateral: bestBid.takerWager,
  maker: '0xMaker...',
  taker: bestBid.taker,
  takerSignature: bestBid.takerSignature,
  takerDeadline: String(bestBid.takerDeadline),
  refCode: '0x' + '00'.repeat(32),
  makerNonce: String(bestBid.makerNonce),
};
 
await writeContract({
  address: '0xPredictionMarket...',
  abi: PredictionMarketAbi,
  functionName: 'mint',
  args: [mintReq],
});