How to Use Wit/Oracle on Celo

 // SPDX-License-Identifier: MIT
pragma solidity ^0.8.11;

import "witnet-solidity-bridge/contracts/interfaces/IWitnetPriceRouter.sol";

contract MyCeloContract {
    IWitnetPriceRouter immutable public router;

    /**
     * IMPORTANT: pass the WitnetPriceRouter address depending on 
     * the network you are using! Please find available addresses here:
     * https://docs.witnet.io/smart-contracts/witnet-data-feeds/addresses
     */
    constructor(IWitnetPriceRouter _router))
        router = _router;
    }

    /// Returns the BTC / USD price (6 decimals), ultimately provided by the Witnet oracle.
    function getBtcUsdPrice() public view returns (int256 _price) {
        (_price,,) = router.valueFor(bytes4(0x24beead4));
    }

    /// Returns the ETH / USD price (6 decimals), ultimately provided by the Witnet oracle.
    function getEthUsdPrice() public view returns (int256 _price) {
        (_price,,) = router.valueFor(bytes4(0x3d15f701));
    }

    /// Returns the BTC / ETH price (6 decimals), derived from the ETH/USD and 
    /// the BTC/USD pairs that were ultimately provided by the Witnet oracle.
    function getBtcEthPrice() public view returns (int256 _price) {
        return (1000000 * getBtcUsdPrice()) / getEthUsdPrice();
    }
}

web3 = Web3(Web3.HTTPProvider('https://forno.celo.org'))
abi = '[{ "inputs": [{ "internalType": "bytes32", "name": "_id", "type": "bytes32" }], "name": "valueFor", "outputs": [{ "internalType": "int256", "name": "", "type": "int256" }, { "internalType": "uint256", "name": "", "type": "uint256" }, { "internalType": "uint256", "name": "", "type": "uint256" }], "stateMutability": "view", "type": "function" }]'
addr = '<WitnetProxy address for Celo>' // copy from docs.witnet.io -> Celo price feeds
contract = web3.eth.contract(address=addr, abi=abi)
// get last value for "Price-CELO/USD-6"
valueFor = contract.functions.valueFor().call("0x9ed884be")
print("Price-CELO/USD-6:", valueFor[0])
print("> lastTimestamp:", valueFor[1])
print("> latestUpdateStatus:", valueFor[2])

// SPDX-License-Identifier: MIT
pragma solidity >=0.7.0 <0.9.0;

import "witnet-solidity-bridge/contracts/interfaces/IWitnetRandomness.sol";

contract MyContract {

    uint32 public randomness;
    uint256 public latestRandomizingBlock;
    IWitnetRandomness immutable public witnet;
    
    /// @param _witnetRandomness Address of the WitnetRandomness contract.
    constructor (IWitnetRandomness _witnetRandomness) {
        assert(address(_witnetRandomness) != address(0));
        witnet = _witnetRandomness;
    }
    
    receive () external payable {}

    function requestRandomNumber() external payable {
        latestRandomizingBlock = block.number;
        uint _usedFunds = witnet.randomize{ value: msg.value }();
        if (_usedFunds < msg.value) {
            payable(msg.sender).transfer(msg.value - _usedFunds);
        }
    }
    
    function fetchRandomNumber() external {
        assert(latestRandomizingBlock > 0);
        randomness = witnet.random(type(uint32).max, 0, latestRandomizingBlock);
    }
}