Blockchain Oracle

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.25;

import { OdfRequest, OdfResponse, IOdfClient, CborReader } from "@opendatafabric/contracts/Odf.sol";

// This sample contract makes an ODF oracle query to calculate
// a Canadian province with the most recorded COVID-19 cases
contract TestConsumer {
    using OdfRequest for OdfRequest.Req;
    using OdfResponse for OdfResponse.Res;
    using CborReader for CborReader.CBOR;

    IOdfClient private oracle;
    string public province;
    int public totalCases;

    // Initialize contract with the oracle address
    constructor(address oracleAddr) {
        oracle = IOdfClient(oracleAddr);
    }

    function initiateQuery() public {
        OdfRequest.Req memory req = OdfRequest.init();

        // Specify ID of the dataset(s) we will be querying.
        // Repeat this call for multiple inputs.
        req.dataset(
            "covid19.canada.case-details",
            "did:odf:fed01c8788dc7825dc95dfaa6c67f989b758d3ebcb1efcb9f47ea914470bd1f7f2bbb"
        );

        // Specify an arbitrary complex SQL query.
        // Queries can include even JOINs
        req.sql(
            "with by_provice as ( "
            "  select "
            "    province, "
            "    count(*) as count "
            "  from 'covid19.canada.case-details' "
            "  group by 1 "
            "), "
            "ranked as ( "
            "  select "
            "    row_number() over (order by count desc) as rank, "
            "    province, "
            "    count "
            "  from by_provice "
            ") "
            "select "
            "  province, "
            "  count "
            "from ranked where rank = 1"
        );

        // Send request to the oracle and specify a callback
        oracle.sendRequest(req, this.onResult);
    }

    // This function will be called by the oracle when
    // request is fulfilled by some data provider
    function onResult(OdfResponse.Res memory result) external {
        // Important: Make sure only the ODF oracle can supply you data
        require(msg.sender == address(oracle), "Can only be called by oracle");

        // We expect only one row: [province, totalCases]
        require(result.numRecords() == 1, "Expected one record");

        CborReader.CBOR[] memory record = result.record(0);
        province = record[0].readString();
        totalCases = record[1].readInt();
    }
}

npm i @opendatafabric/contracts

{
    "query": "select offset, city, population from populations order by offset desc",
    "queryDialect": "SqlDataFusion",
    "datasets": [{
        "id": "did:odf:fed0119d20360650afd3d412c6b11529778b784c697559c0107d37ee5da61465726c4",
        "alias": "populations"
    }],
    "dataFormat": "JsonAoA",
    "include": ["input"],
}

{
    "input": {
        "query": "select offset, city, population from populations order by offset desc",
        "queryDialect": "SqlDataFusion",
        "dataFormat": "JsonAoA",
        "include": ["Input"],
        "datasets": [{
            "id": "did:odf:fed0119d20360650afd3d412c6b11529778b784c697559c0107d37ee5da61465726c4",
            "alias": "populations",
            "blockHash": "f1620708557a44c88d23c83f2b915abc10a41cc38d2a278e851e5dc6bb02b7e1f9a1a"
        }]
    },
    "output": {
        "data": [
            [1, "B", 200], 
            [0, "A", 100]
        ],
        "dataFormat": "JsonAoa"
    }
}

function testResponseDecoding() public pure {
    bytes memory responseBytes = hex"8501F58A826..92AFE32";
    OdfResponse.Res memory res = OdfResponse.fromBytes(0, responseBytes);
    assertEq(res.numRecords(), 10);
    CborReader.CBOR[] memory record = res.record(0);
    string memory voiceId = record[0].readString();
    int256 playtimeTotal = record[1].readInt();
    assertEq(voiceId, "lana-del-rey");
    assertEq(playtimeTotal, 6449);
}