Hardhat relay compatibility (#334)

* Add hardhat scripts for contract and user interactions

Signed-off-by: nikolay <[email protected]>

* Add readme

Signed-off-by: nikolay <[email protected]>

* Fix code smells

Signed-off-by: nikolay <[email protected]>

* Add relay endpoint url in .env

Signed-off-by: nikolay <[email protected]>

* Uncomment tests

Signed-off-by: nikolay <[email protected]>

* Add license headers

Signed-off-by: nikolay <[email protected]>

Author: natanasow

tools/hardhat-example/.env.example

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+OPERATOR_PRIVATE_KEY=
+RECEIVER_PRIVATE_KEY=
+RELAY_ENDPOINT='http://localhost:7546'

tools/hardhat-example/.gitignore

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+node_modules
+.env
+coverage
+coverage.json
+typechain
+typechain-types
+
+#Hardhat files
+cache
+artifacts

tools/hardhat-example/README.md

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+# Hardhat example
+
+Simple scripts for basic operations like hbars transfer, balance fetching, and contract interactions (deployment and calls).
+
+## Prerequisite
+You must have running:
+- JSON-RPC Relay
+
+## Configuration
+
+Create `.env` file based on `.env.example`
+```
+# Alias accounts keys
+OPERATOR_PRIVATE_KEY=
+RECEIVER_PRIVATE_KEY=
+
+```
+
+## Setup & Install
+
+In the project directory:
+
+1. Run `npm install`
+2. Run `npx hardhat test`

tools/hardhat-example/contracts/Greeter.sol

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+//SPDX-License-Identifier: Unlicense
+pragma solidity ^0.8.0;
+
+contract Greeter {
+    string private greeting;
+
+    constructor(string memory _greeting) {
+        greeting = _greeting;
+    }
+
+    function greet() public view returns (string memory) {
+        return greeting;
+    }
+
+    function setGreeting(string memory _greeting) public {
+        greeting = _greeting;
+    }
+}

tools/hardhat-example/hardhat.config.js

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+/*-
+ *
+ * Hedera JSON RPC Relay - Hardhat Example
+ *
+ * Copyright (C) 2022 Hedera Hashgraph, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+require('dotenv').config();
+require('@nomicfoundation/hardhat-toolbox');
+
+task('show-balance', async () => {
+  const showBalance = require('./scripts/showBalance');
+  return showBalance();
+});
+
+task('transfer-hbars', async () => {
+  const transferHbars = require('./scripts/transferHbars');
+  return transferHbars();
+});
+
+task('deploy-contract', async () => {
+  const deployContract = require('./scripts/deployContract');
+  return deployContract();
+});
+
+task('contract-view-call', async (taskArgs) => {
+  const contractViewCall = require('./scripts/contractViewCall');
+  return contractViewCall(taskArgs.contractAddress);
+});
+
+task('contract-call', async (taskArgs) => {
+  const contractCall = require('./scripts/contractCall');
+  return contractCall(taskArgs.contractAddress, taskArgs.msg);
+});
+
+module.exports = {
+  solidity: '0.8.4',
+  defaultNetwork: 'relay',
+  networks: {
+    relay: {
+      url: process.env.RELAY_ENDPOINT
+    }
+  }
+};