Architectural overview

Overview

Jam's off-chain TypeScript backend assists in generating blockchain transactions tailored for multi-step DeFi operations. The backend performs computations to output a series of actions (transaction steps) to be executed in a batch, which will then be invoked via an ERC-4337-compatible wallet using DELEGATECALL. This documentation covers the key classes and functions exposed by the backend for transaction generation.

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AssetStore

The AssetStore class is responsible for managing and accessing information about different assets (tokens).

Constructor

constructor(assets: Asset[])

Parameters

• assets: An array of Asset objects containing information like asset id, chain id, symbol, etc.

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Asset

A type directly derived from asset' JSON objects, with the following parameters:

export interface Asset {
  id: string;
  name: string;
  chainId: number;
  active: boolean;
  address: string;
  color: string;
  decimals: number;
  symbol: string;
  type: AssetType;
  visible: boolean;
  linkedAssets?: LinkedAsset[];
  maxSize?: number;
  allowSlot?: number;
  balanceSlot?: number;
  callParams?: any;
  price?: number;
  isVyper?: boolean;
}

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generateTransaction

The function takes in details about input and output assets and generates a series of steps for a multi-step transaction.

Syntax

async function generateTransaction({
  chainId,
  walletAddress,
  inputAllocation,
  outputAllocation,
  assetStore,
}: {
  chainId: number;
  walletAddress: string;
  assetStore: AssetStore;
  inputAllocation: AbsoluteAllocation;
  outputAllocation: FractionAllocation;
})

Parameters

• chainId: Chain ID to specify on which blockchain network the transaction should occur.

• walletAddress:

• assetStore: An instance of the AssetStore class to fetch details about assets.

• inputAllocation: An array describing which assets and how much of them should be used as input.

• outputAllocation: An array describing how the output should be allocated among different assets.

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Types

AbsoluteAllocationItem

Type used to define an item in the input allocation array.

interface AbsoluteAllocationItem {
  assetId: string;
  amountStr: BigNumberish;
}

• assetId: Unique identifier for the asset.

• amountStr: The amount of the asset in string format, compatible with BigNumber libraries.

FractionAllocationItem

Type used to define an item in the output allocation array.

interface FractionAllocationItem {
  assetId: string;
  fraction: number;
  rewards?: FractionAllocationItem[];
}

• assetId: Unique identifier for the asset.

• fraction: A float (0-1) representing the fraction of the output asset.

• rewards: Optional, additional nested FractionAllocationItems for cases like staking rewards.

Utility Types

• AbsoluteAllocation: Array of AbsoluteAllocationItem.

• FractionAllocation: Array of FractionAllocationItem.