Credential.sol

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.6.0 <0.7.0;
pragma experimental ABIEncoderV2;

import "./CredentialSchema.sol";

contract CredContract is CredentialSchema {
    struct Credential {
        string id;
        string owner;
        string issuer;
        string ipfsHash;
    }

    event GiveAccess(string mssg);
    event RevokeAccess(string mssg);
    event SendMessage(string mssg);
    event CreateCredential(string did);
    event GetCredential(Credential credential);

    mapping(string => string[]) accessStore;
    mapping(string => Credential) credentialStore;

    function giveAccess(
        string memory ownerDID,
        string memory credDID,
        string memory receiverDID
    ) public checkDidExists(ownerDID) checkDidExists(receiverDID) {
        require(
            bytes(credentialStore[credDID].id).length != 0,
            "Credential Schema does not exist"
        );
        Credential memory tempCred = credentialStore[credDID];
        require(
            keccak256(abi.encodePacked(ownerDID)) ==
                keccak256(abi.encodePacked(tempCred.owner)),
            "Not the owner"
        );
        string[] storage tempArr = accessStore[receiverDID];
        for (uint256 i = 0; i < tempArr.length; i++) {
            if (
                keccak256(abi.encodePacked(credDID)) ==
                keccak256(abi.encodePacked(tempArr[i]))
            ) {
                emit GiveAccess("Access already given");
                return;
            }
        }
        tempArr.push(credDID);
        accessStore[receiverDID] = tempArr;
        emit GiveAccess("Access given to new user");
    }

    function revokeAccess(
        string memory ownerDID,
        string memory credDID,
        string memory receiverDID
    ) public checkDidExists(ownerDID) checkDidExists(receiverDID) {
        require(
            bytes(credentialStore[credDID].id).length != 0,
            "Credential Schema does not exist"
        );
        Credential memory tempCred = credentialStore[credDID];
        require(
            keccak256(abi.encodePacked(ownerDID)) ==
                keccak256(abi.encodePacked(tempCred.owner)),
            "Not the owner"
        );
        string[] storage tempArr = accessStore[receiverDID];
        for (uint256 i = 0; i < tempArr.length; i++) {
            if (
                keccak256(abi.encodePacked(credDID)) ==
                keccak256(abi.encodePacked(tempArr[i]))
            ) {
                emit RevokeAccess("Access revoked");
                delete tempArr[i];
                accessStore[receiverDID] = tempArr;
                return;
            }
        }
        emit RevokeAccess("No access to begin with");
    }

    function getCredential(string memory did, string memory receiverDID)
        public
        returns (Credential memory)
    {
        require(
            bytes(credentialStore[did].id).length != 0,
            "Credential does not exist"
        );
        string[] memory tempArr = accessStore[receiverDID];
        for (uint256 i = 0; i < tempArr.length; i++) {
            if (
                keccak256(abi.encodePacked(did)) ==
                keccak256(abi.encodePacked(tempArr[i]))
            ) {
                emit GetCredential(credentialStore[did]);
                return credentialStore[did];
            }
        }
        revert("No access to the credential");
    }

    function createCredential(
        string memory ownerDID,
        string memory issuerDID,
        string memory hash,
        string memory ipfsHash
    )
        public
        checkDidExists(ownerDID)
        checkDidExists(issuerDID)
        returns (string memory)
    {
        bytes memory b = abi.encodePacked("did:cred:");
        b = abi.encodePacked(b, hash);
        string memory did = string(b);
        credentialStore[did].id = did;
        credentialStore[did].owner = ownerDID;
        credentialStore[did].issuer = issuerDID;
        credentialStore[did].ipfsHash = ipfsHash;
        string[] storage tempArr = accessStore[ownerDID];
        tempArr.push(did);
        accessStore[ownerDID] = tempArr;
        tempArr = accessStore[issuerDID];
        tempArr.push(did);
        accessStore[issuerDID] = tempArr;
        emit CreateCredential(did);
        return did;
    }
}