trading.js

const { ClobClient, OrderType, Side } = require('@polymarket/clob-client');
const { ethers } = require('ethers');
require('dotenv').config();

// Initialize Client
async function initClient() {
    const provider = new ethers.JsonRpcProvider('https://polygon-rpc.com');
    const wallet = new ethers.Wallet(process.env.PRIVATE_KEY, provider);

    // You might need to change chainId to 137 (Polygon Mainnet) if testing live
    const clobClient = new ClobClient(
        'https://clob.polymarket.com',
        137,
        wallet
    );

    // Perform L2 Auth headers derivation
    // In a real script, you might want to cache the creds
    const creds = await clobClient.deriveApiKey();

    console.log("CLOB Client Initialized for address:", wallet.address);
    return clobClient;
}

/**
 * Places a limit order to BUY (Long/Short outcome token)
 */
async function enterPosition(client, marketId, side, amount, price) {
    // Basic Error Checking
    if (!client) throw new Error("Client not initialized");

    console.log(`Attempting to ENTER: ${side} ${amount} @ ${price}`);

    try {
        const order = await client.createOrder({
            tokenID: marketId, // Token ID of the outcome (Yes or No token)
            price: price, // Limit price
            side: side === 'BUY' ? Side.Buy : Side.Sell, // Usually 'BUY' to enter
            size: amount, // Amount of shares
            feeRateBps: 0, // Maker orders often 0, check docs
            nonce: Date.now(), // Unique nonce
        });

        const resp = await client.postOrder(order);
        console.log("Order Placed:", resp);
        return resp;
    } catch (err) {
        console.error("Failed to Enter Position:", err.message);
    }
}

/**
 * Places a limit order to SELL (closing the position)
 */
async function exitPosition(client, marketId, side, amount, price) {
    console.log(`Attempting to EXIT: ${side} ${amount} @ ${price}`);

    // To exit a long position, we SELL.
    // If we bought 'YES' tokens, we now SELL 'YES' tokens.

    try {
        const order = await client.createOrder({
            tokenID: marketId,
            price: price,
            side: side === 'BUY' ? Side.Buy : Side.Sell, // 'SELL' to exit usually
            size: amount,
            feeRateBps: 0,
            nonce: Date.now(),
        });

        const resp = await client.postOrder(order);
        console.log("Exit Order Placed:", resp);
        return resp;
    } catch (err) {
        console.error("Failed to Exit Position:", err.message);
    }
}

module.exports = {
    initClient,
    enterPosition,
    exitPosition
};