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Farming contracts

Overview

About

1inch farming contract offers protocols to give rewards to users holding specific tokens. The repository offers two ways to get incentivisation rewards to holders:

• Token smart contract could be derived from ERC20Hooks and allow farming in multiple farms without necessarity staking token to any pool. User should add farm as a hook (see ERC20Hooks concept) and keep tokens on its address to be eligible for rewards.
• A user can stake/deposit specific tokens to FarmingPool smart contract. It is less convenient way and is only used for backward compatibility for those smart contracts that have been deployed and there are no way to change it.

Math

Farming reward is distributed uniformly across the whole farming period and depends on number of participants. Actually, the reward is a piecewise linear function which is set by formula

$$ R_p= \sum{ R \ * \frac {t}{T} *\ \frac {V}{V_{total}} } $$

where $R_p$ - total farming reward for a farming participant

R - total reward locked for farming

t - time period duration (between farm's joins and/or exits)

T - total farming duration

V - participant's farmable tokens share

$V_{total}$ - total number of farmable tokens joined the farm

Example

Given $72 000 reward is locked for 5 weeks in a farm and there are three farmers

• Farmer 1 joins at week 1 with 100 farmable tokens on his balance but exits at week 2 and rejoins at week 3. At week 4 he increases his balance up to 200 farmable tokens
• Farmer 2 joins at week 2 with 300 farmable tokens and exits after week 3
• Farmer 3 joins at week 2 with 300 farmable tokens but decreases his farmable token balance after week 3 down to 100 and exits at week 4

72000$ reward	Week 1	Week 2	Week 3	Week 4
Farmer 1	100		100	200
Farmer 2		300	300
Farmer 3		300	100

The resulting reward distribution would be the following

	Week 1	Week 2	Week 3	Week 4
Farmer 1	18000		3600	18000
Farmer 2		9000	10800
Farmer 3		9000	3600

More examples are here @1inch/farming/TESTS.md#deposit

ERC20Hooks and FarmingHook usage

Concept

To start new farming owner should deploy (or use already deployed) farming for a pair of tokens and initialize it.

1. Deploy farm and set farmable and reward token
2. Start farming
   • Set distributor
   • From distributor account send reward amount and set farming period

When farming is started users holding farmable tokens may addHook the farm to accumulate rewards. After joining a farm, a user starts to get farm rewards for the whole amount of farmable tokens he owns. When a user's balance changes the reward share is changed automatically.

If a user wants to stop participating in farming he should removeHook the farm with. Rewards for previous farming periods may be claimed any time with claim function of the farm regardless if a user is still farming or has already exited the farm.

A user may join several farms which provide rewards for the same token.

To prevent new farmings from starting an owner may set a distributor address to zero.

Installation

$ npm install @1inch/farming

or

$ yarn add @1inch/farming

Usage

Once installed, you can use the contracts in the library by importing them. Just use ERC20Hooks instead of ERC20 to derive from

pragma solidity ^0.8.0;

import "@1inch/farming/contracts/ERC20Hooks.sol";

contract AMMPoolToken is ERC20Hooks {
    constructor(uint256 farmsLimit) ERC20("AMMPoolToken", "AMM") ERC20Hooks(farmsLimit) {
    }
}

Optimizations

Storage access:

• 1 storage slot for farming params, updated only on farming restarting:

  solidity uint40 public finished; uint32 public duration; uint184 public reward;

• 1 storage slot for farming state, updated only on changing number of farming tokens:

  solidity uint40 public checkpoint; uint216 public farmedPerTokenStored;

• 1 storage slot per each farmer, updated on deposits/withdrawals (kudos to @snjax):

  solidity mapping(address => int256) public corrections;

• Compact address array is used for storing farms per user/wallet. Array length is stored in high bits of the first array item:

  • @1inch/solidity-utils/AddressArray.sol

FarmingPool usage

The FarmingPool usage is almost the same but a farmer has to deposit farmable tokens to farm account and withdraw it after the farming is completed.