Transformers

The transformers are responsible to track the data of contributions and extractions through the events fired by the smart contracts.

Structure

The structure of the transformers is quite similar to The Graph subgraphs in which we have functions named event handlers containing event objects as arguments.

Each transformer belongs to one contract.

type Transformer = {
 address?:string;
 getAddresses?:(chain:Chain) => Promise<Array<string>>;
 contract: Interface;
 eventHandlers: Record<Signature,EventHandler>;
 startBlock:number;
}

Property	Type	Description
address	optional	Contract address, if undefined will sync all the events of given signatures in event handlers
getAddresses	optional	If you have a mapping of contract addresses and want to sync events for all those addresses
contract	required	The interface of contract generated by typechain through contract ABI
eventHandlers	required	It's the key value object in which the key is the signature (keccak256 hash of event topic) of the event and the value is the callback function that will be executed when the event gets fired
startBlock	required	Block number from which the syncing of contract events will start

Event Handler

The event handler is basically a function linked with its signature that is called when a specific event is fired. It takes event data as an argument and returns protocol value (contribution/extraction).

type EventHandler = (
  event: Event<any>
) => Promise<ProtocolValueReturnType | void | undefined>;

Event (passed as an argument in the event handler)

import {
  TransactionResponse,
  Block,
  TransactionReceipt,
} from '@ethersproject/providers';

interface Event<T> {
  address: string;
  blockNumber: number;
  params: T;
  signature: string;
  block: Promise<Block>;
  transaction: Promise<TransactionResponse>;
  transactionReceipt: Promise<TransactionReceipt>;
  transactionHash: string;
  transactionLogIndex: number;
  logIndex: number;
  chain: Chain;
}

Protocol Value (returned by event handler)

type ProtocolValueReturnType = {
  type: 'contribution' | 'extraction';
  label: string;
  value: number;
  user: string;
};