Viewing status

Advanced orders / Eth-Flow

Part 2/ Eth-Flow/Viewing status

One of the more difficult things to do with Eth-flow orders is to determine their status, as to do so we need to know the orderUid of the order.

In this tutorial, we will learn how to determine the orderUid of an Eth-flow order, and how to use it to determine the order's status.

Determining the orderUid

Upon consulting the documentation's Technical reference on orderUid, we can see that the orderUid is composed of the following fields:

• digest: The EIP-712 digest of the GPv2Order.Data struct
• owner: The address of the order's owner
• expiry: The order's expiry timestamp

For the case of all Eth-flow orders, it is immediately apparent that:

• The owner is the address of the Eth-flow contract (they are just simple ERC-1271 orders signed by the Eth-flow contract)
• The expiry is the maximum possible value for a uint32, ie. 2^32 - 1

Therefore, we can create a function that takes an ABI-encoded GPv2Order.Data struct, and returns the corresponding Eth-flow orderUid:

import type { Web3Provider } from '@ethersproject/providers'
import { utils } from "ethers";
import { SupportedChainId } from '@cowprotocol/cow-sdk'
import { onchainOrderToHash } from "/src/lib/gpv2Order";
import abi from './ethFlow.abi.json'

export async function run(provider: Web3Provider): Promise<unknown> {
	// ...

	const ethFlowOrderUid = (onchainOrder: any) => {
		const hash = onchainOrderToHash(onchainOrder, chainId);
		return hash + ethFlowAddress.slice(2) + 'ffffffff';
	}

	// ...
}

Unfortunately there are no functions exported (yet) from the cow-sdk that allow for computing the EIP-712 digest of an ABI-encoded GPv2Order.Data struct. The onchainOrderToHash function is defined in the gpv2Order.ts file and usable for this tutorial.

Contract (CoWSwapEthFlow) OrderPlacement events

For handling events from the smart contracts, the tutorials use ethers.js.

To handle events, we need to know:

• the ABI
• the contract address (optional, but recommended)

In the case of this tutorial, we already have the ABI from the previous tutorial, and we can use the ethFlowAddress constant from the previous tutorial.

Get transaction receipt

The CoWSwapEthFlow contract emits an OrderPlacement event whenever an order is created. This event log contains an order field, which is the GPv2Order.Data struct that we need to determine the orderUid.

Let's use a known transaction hash to extract the GPv2Order.Data struct from the OrderPlacement event:

import type { Web3Provider } from '@ethersproject/providers'
import { utils } from "ethers";
import { SupportedChainId } from '@cowprotocol/cow-sdk'
import abi from './ethFlow.abi.json'

export async function run(provider: Web3Provider): Promise<unknown> {
	// ...

	const txHash = '0x04d05fc2c953cc63608c19a79869301d62b1f077e0f795f716619b21f693f00c';
	const receipt = await provider.getTransactionReceipt(txHash);
}

Process event logs

Now that we have the transaction receipt, we can extract the OrderPlacement event logs from it:

// ...

export async function run(provider: Web3Provider): Promise<unknown> {
	// ...

	const ethFlowOrderUids: string[] = receipt.logs
		.reduce((orderIds, log) => {
			if (log.address !== ethFlowAddress) {
				return orderIds;
			}

			const parsedLog = iface.parseLog(log);
			if (parsedLog.name === 'OrderPlacement') {
				const [, order, ,] = parsedLog.args;

				orderIds.push(ethFlowOrderUid(order));
			}
			
			return orderIds;
		}, []);
}

Above we:

• Filter out all logs that are not from the ethFlowAddress (i.e. this way we force that we don't accidentally look at logs from the other environment's CoWSwapEthFlow contract)
• Parse the log using the ABI
• Extract the GPv2Order.Data struct from the data field of the OrderPlacement event
• Compute the orderUid from the GPv2Order.Data struct using the ethFlowOrderUid function defined above
• Filter out any undefined values (i.e. logs that were not OrderPlacement events and/or were not from the ethFlowAddress)

Run the code

To run the code, we can press the "Run" button in the bottom right panel (the web container).

When running the script, we may be asked to connect a wallet. We can use Rabby for this.

1. Accept the connection request in Rabby
2. Press the "Run" button again
3. Observe the calculated orderUid in the output panel

Now that we have determined the orderUid of an Eth-flow order, we can simply look up the order's status using CoW Explorer.