README.md

Yggdrasil Data Engine Contracts

This repository contains the smart contracts for interacting with Yggdrasil's data feed services on both EVM-compatible chains and Cosmos chains. These contracts allow you to retrieve real-time price data directly into your decentralized applications (dApps).

Overview

Yggdrasil provides data feeds that can be integrated into your smart contracts to access real-time pricing information. This repository includes example contracts and implementation guidelines for both EVM and Cosmos ecosystems.

Table of Contents

• Yggdrasil Data Engine Contracts
  • Overview
  • Table of Contents
  • Getting Started
    • EVM-Compatible Chains
      • Interface Definition
      • Implementation Example
      • Callback Function
    • Cosmos Chains
      • Getting the Data Feed Address
      • Using Data Feed Crate
      • Requesting Data Feeds
      • Handling the Price Feed Response
  • License

Getting Started

EVM-Compatible Chains

To integrate Yggdrasil's data feeds into your Solidity smart contracts, you need to implement the IDataFeed interface.

Interface Definition

interface IDataFeed {
    function requestPrices(
        bytes32[] calldata _assets,
        function(uint8[] memory, uint256[] memory) external _callback
    ) external payable;

    function feePerAsset() external view returns (uint256);
}

requestPrices: Requests the price data for the specified assets and handles the response through the provided callback function. feePerAsset: Returns the fee required per asset for the request.

Implementation Example

Here’s an example implementation that demonstrates how to interact with the IDataFeed interface:

contract DataFeedInteractor  {
    address public constant PRICE_FEED_PROXY = 0x30B3731d5fE29E768Ab282dBF2c79D9A70776Ad0; // Data Feed Address on Arbitrum Sepolia
    IDataFeed public priceFeed;

    uint8[] public lastDecimals;
    uint256[] public lastPrices;

    event PricesReceived(uint8[] decimals, uint256[] prices);

    constructor() {
        priceFeed = IDataFeed(PRICE_FEED_PROXY);
    }

    function requestPrices(bytes32[] calldata _assets) external payable {
        uint256 totalFee = priceFeed.feePerAsset() * _assets.length;
        require(msg.value >= totalFee, "Insufficient fee");

        priceFeed.requestPrices{value: totalFee}(_assets, this.dataCallback);

        if (msg.value > totalFee) {
            payable(msg.sender).transfer(msg.value - totalFee);
        }
    }

    function dataCallback(uint8[] memory _decimals, uint256[] memory _prices) external {
        require(msg.sender == PRICE_FEED_PROXY, "Unauthorized callback");

        lastDecimals = _decimals;
        lastPrices = _prices;

        emit PricesReceived(_decimals, _prices);
    }

    function getLastPrices() external view returns (uint8[] memory, uint256[] memory) {
        return (lastDecimals, lastPrices);
    }

    receive() external payable {}
}

Callback Function

The dataCallback function processes the response from the requestPrices function. It stores the received prices and decimals in state variables and emits an event for further use.

Cosmos Chains

For Cosmos chains, the integration is done using Rust and the price-feeds crate.

Getting the Data Feed Address

Before you can request price data, you'll need the appropriate data feed contract address for the Cosmos chain you are working with.

Using Data Feed Crate

Add the following dependency to your Cargo.toml file to use the Yggdrasil data feeds in your contracts:

price-feeds = "0.1.1"

use price_feeds::{RequestPriceFeed}; 
use price_feeds::msg::{PriceFeedResponse};

pub fn execute_request_single_price(
    deps: DepsMut,
    _info: MessageInfo,
    pair : String,
) -> Result<Response, ContractError> {
    let price_feed_contract = PRICE_FEED_CONTRACT.load(deps.storage)?;
    
    let request_msg = WasmMsg::Execute {
        contract_addr: deps.api.addr_validate(&price_feed_contract)?.to_string(),
        msg: to_json_binary(&RequestPriceFeed { symbol: pair})?,
        funds: vec![Coin{
            denom : "uom".to_string(), 
            amount: Uint128::new(1000)
        }],
    };

    Ok(Response::new()
        .add_message(request_msg)
        .add_attribute("action", "request_single_price")
    )
}

pub fn execute_receive_price(
    deps: DepsMut,
    _env: Env,
    _info: MessageInfo,
    price_response: PriceFeedResponse,
) -> Result<Response, ContractError> {
    let price_feed = PriceFeed {
        price: price_response.price,
    };

    PRICE_FEEDS.save(deps.storage, price_response.symbol, &price_feed)?;

    Ok(Response::new()
        .add_attribute("action", "receive_price")
        .add_attribute("price", price_response.price.to_string()))
}

License

This project is licensed under the MIT License - see the LICENSE file for details.

You can copy and paste this Markdown code directly into your `README.md` file in your GitHub repository.