Merge pull request ethereum-optimism#137 from ethereum-optimism/20221…

…102-attestations

feat(AttestationStation): Simple tutorial

ecosystem/attestation-station/.env.example

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+# Put the mnemonic for an account on Optimism here
+MNEMONIC=test test test test test test test test test test test junk
+
+# API KEY for Alchemy
+ALCHEMY_API_KEY=
+
+# URL to access Optimism Goerli (if not using Alchemy)
+OPTIMISM_GOERLI_URL=

ecosystem/attestation-station/README.md

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+# AttestationStation Contract
+
+[![Discord](https://img.shields.io/discord/667044843901681675.svg?color=768AD4&label=discord&logo=https%3A%2F%2Fdiscordapp.com%2Fassets%2F8c9701b98ad4372b58f13fd9f65f966e.svg)](https://discord-gateway.optimism.io)
+[![Twitter Follow](https://img.shields.io/twitter/follow/optimismFND.svg?label=optimismFND&style=social)](https://twitter.com/optimismFND)
+
+The AttestationStation Contract smart contract contains a public `attestations` mapping that anyone can write to and read from.
+In this tutorial you learn how to read, interpret, and write those attestations.
+
+The contract we'll be using is on the Optimism Goerli network, at address [`0x3Ca8c0B5608AE3E4D3b4d29b2699C5fCc0e67f3d`](https://goerli-optimism.etherscan.io/address/0x3Ca8c0B5608AE3E4D3b4d29b2699C5fCc0e67f3d).
+
+## Prerequisites
+
+- You have [Node.js](https://nodejs.org/en/) running on your computer, as well as [yarn](https://classic.yarnpkg.com/lang/en/).
+- There is network connectivity to a provider on the Optimism Goerli network, and to the npm package registry.
+
+
+## Setup
+
+1. Use `yarn` to download the packages you need
+
+   ```sh
+   yarn
+   ```
+
+
+1. Copy `.env.example` to `.env` and modify the parameters:
+
+   - `MNEMONIC` is the mnemonic to an account that has enough ETH to pay for the transaction.
+
+   - `ALCHEMY_API_KEY` is the API key for an Optimism Goerli app on [Alchemy](https://www.alchemy.com/), our preferred provider.
+
+   - `OPTIMISM_GOERLI_URL` is the URL for Optimism Goerli, if you use [a different node provider](https://community.optimism.io/docs/useful-tools/providers/).
+
+
+1. Enter the hardhat console:
+
+   ```sh
+   yarn hardhat console --network optimism-goerli
+   ```
+
+
+1. Attach to the contract on the Optimism Goerli network:
+
+   ```js
+   AttestationStation = await ethers.getContractFactory("AttestationStation")
+   attestationStation = AttestationStation.attach("0x3Ca8c0B5608AE3E4D3b4d29b2699C5fCc0e67f3d")
+   ```
+
+
+## Write an attestation
+
+1. Create the attestation.
+
+   ```js
+   goatAddr = '0x00000000000000000000000000000000000060A7'
+   attendedKey = ethers.utils.keccak256(ethers.utils.toUtf8Bytes("animal-farm.school.attended"))
+   attestation = {
+       about: goatAddr,
+       key: attendedKey,
+       val: 1   // for true
+   }
+   ```
+
+
+1. Send the attestation.
+   Note that `attestationStation.attest` accepts an array as parameter, so you'll be able to attest to many facts in a single transaction.
+
+   ```js
+   tx = await attestationStation.attest([attestation])
+   rcpt = await tx.wait()
+   ```
+
+
+## Read attestations
+
+To read an attestation you need to know three things:
+
+- Creator address (who attested this)
+- Subject address (who is being attested about)
+- Key
+
+1. Read the value for the attestation you just created.
+
+   ```js
+   creatorAddr = (await ethers.getSigner()).address
+   (await attestationStation.attestations(creatorAddr, goatAddr, attendedKey) != '0x')
+   ```
+
+1. Check the attestation for a different address to see that the default is false
+
+   ```js
+   notGoatAddr = '0x000000000000000000000000000000000000BEEF'
+   (await attestationStation.attestations(creatorAddr, notGoatAddr, attendedKey) != '0x')
+   ```
+
+1. Read an attestation created by a different user (this one is a grade, so it's text)
+
+   ```js
+   historyKey = ethers.utils.keccak256(ethers.utils.toUtf8Bytes("animal-farm.school.grades.history"))
+   hex = await attestationStation.attestations('0xBCf86Fd70a0183433763ab0c14E7a760194f3a9F', goatAddr, historyKey)
+   ethers.utils.toUtf8String(hex)
+   ```
+
+   Note: To create the attestation with an ascii value I used this data structure:
+
+   ```js
+   attestation = {
+      about: goatAddr, 
+      key: historyKey, 
+      val: ethers.utils.toUtf8Bytes("A+")
+   }
+   ```

ecosystem/attestation-station/contracts/AttestationStation.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.17;
+
+contract AttestationStation {
+    mapping(address => mapping(address => mapping(bytes32 => bytes))) public attestations;
+
+    struct AttestationData {
+        address about;
+        bytes32 key;
+        bytes val;
+    }
+
+    event AttestationCreated(
+        address indexed creator,
+        address indexed about,
+        bytes32 indexed key,
+        bytes val
+    );
+
+    function attest(AttestationData[] memory _attestations) public {
+        for (uint256 i = 0; i < _attestations.length; ++i) {
+            AttestationData memory attestation = _attestations[i];
+            attestations[msg.sender][attestation.about][attestation.key] = attestation.val;
+            emit AttestationCreated(
+                msg.sender,
+                attestation.about,
+                attestation.key,
+                attestation.val
+            );
+        }
+    }
+}

ecosystem/attestation-station/hardhat.config.js

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+require("@nomiclabs/hardhat-waffle");
+require('dotenv').config()
+
+// This is a sample Hardhat task. To learn how to create your own go to
+// https://hardhat.org/guides/create-task.html
+task("accounts", "Prints the list of accounts", async (taskArgs, hre) => {
+  const accounts = await hre.ethers.getSigners();
+
+  for (const account of accounts) {
+    console.log(account.address);
+  }
+});
+
+// You need to export an object to set up your config
+// Go to https://hardhat.org/config/ to learn more
+
+/**
+ * @type import('hardhat/config').HardhatUserConfig
+ */
+
+const optimismGoerliUrl = 
+  process.env.ALCHEMY_API_KEY ? 
+    `https://opt-goerli.g.alchemy.com/v2/${process.env.ALCHEMY_API_KEY}` :
+    process.env.OPTIMISM_GOERLI_URL
+
+const words = process.env.MNEMONIC.match(/[a-zA-Z]+/g).length
+validLength = [12, 15, 18, 24]
+if (!validLength.includes(words)) {
+   console.log(`The mnemonic (${process.env.MNEMONIC}) is the wrong number of words`)
+   process.exit(-1)
+}
+
+module.exports = {
+  solidity: "0.8.17",
+  networks: {
+    "local-devnode": {
+       url: "http://localhost:8545",
+       accounts: { mnemonic: "test test test test test test test test test test test junk" }
+    },
+    "optimism-goerli": {
+       url: optimismGoerliUrl,
+       accounts: { mnemonic: process.env.MNEMONIC }
+    }
+  }
+};

ecosystem/attestation-station/package.json

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+{
+  "name": "hardhat-project",
+  "devDependencies": {
+    "@nomiclabs/hardhat-ethers": "^2.0.5",
+    "@nomiclabs/hardhat-waffle": "^2.0.2",
+    "chai": "^4.3.6",
+    "ethereum-waffle": "^3.4.0",
+    "ethers": "^5.5.4",
+    "hardhat": "^2.8.4"
+  },
+  "dependencies": {
+    "dotenv": "^16.0.0"
+  }
+}