feat: add listeners scaffolding

.env.example

@@ -0,0 +1,12 @@
+# Web3---
+FACTORY_ADDRESS=0x9fDd978101EF4F7A3AE5AEC08898258b5CDBF52B
+PROVIDER_URL=https://kovan.infura.io/v3/<secret-key>
+# The block time is used calculate how many blocks to scan when fetching
+# logs and avoid rate limiting by web3 providers.
+BLOCK_TIME_MILLISECONDS=4000
+
+# The bot learns the addresses of TCRs to watch by fetching logs,
+# emitted by the factory. We can fetch logs more quickly by
+# sweeping the blockchain from the deployment block of the factory contract.
+# This field is optional, if not set, 0 will be used.
+FACTORY_BLOCK_NUM=16384123

package.json

@@ -23,6 +23,10 @@
     "gtcr",
     "bot"
   ],
+  "dependencies": {
+    "@kleros/tcr": "^1.7.1",
+    "ethers": "^4.0.46"
+  },
   "devDependencies": {
     "@commitlint/cli": "^8.3.5",
     "@commitlint/config-conventional": "^8.3.4",

src/handlers/index.ts

@@ -0,0 +1,20 @@
+import { ethers } from 'ethers'
+
+import requestSubmittedHandler from './request-submitted'
+import requestResolvedHandler from './request-resolved'
+
+export default async function addTCRListeners(tcr: ethers.Contract) {
+  // Submissions and removal requests.
+  tcr.on(
+    tcr.filters.RequestSubmitted(),
+    requestSubmittedHandler()
+  )
+
+  // Request resolved.
+  tcr.on(
+    tcr.filters.ItemStatusChange(null, null, null, null, true),
+    requestResolvedHandler()
+  )
+
+  console.info(`Done setting up listeners for ${tcr.address}`)
+}

src/handlers/request-resolved.ts

@@ -0,0 +1,4 @@
+export default () => async () => {
+  // TODO: Stop monitoring item.
+  // TODO: Withdraw pending crowdfunding rewards.
+}

src/handlers/request-submitted.ts

@@ -0,0 +1,3 @@
+export default () => async () => {
+  // TODO: Add to DB and start monitoring.
+}

src/index.ts

@@ -1 +1,82 @@
-// TODO
+import { ethers } from 'ethers'
+
+import _GTCRFactory from '@kleros/tcr/build/contracts/GTCRFactory.json'
+import _GeneralizedTCR from '@kleros/tcr/build/contracts/GeneralizedTCR.json'
+
+// Run env variable checks.
+import './utils/env-check'
+import addTCRListeners from './handlers'
+
+const provider = new ethers.providers.JsonRpcProvider(process.env.PROVIDER_URL)
+provider.pollingInterval = 60 * 1000 // Poll every minute.
+
+const gtcrFactory = new ethers.Contract(
+  process.env.FACTORY_ADDRESS as string,
+  _GTCRFactory.abi,
+  provider
+)
+
+// Run bot.
+;(async () => {
+  // Initial setup.
+  console.info('Booting...')
+  console.info()
+  const [currBlock, network] = await Promise.all([
+    provider.getBlockNumber(),
+    provider.getNetwork()
+  ])
+
+  console.info(`Connected to ${network.name} of chain of ID ${network.chainId}`)
+  console.info(`GTCR Factory deployed at ${process.env.FACTORY_ADDRESS}`)
+
+  // Fetch all TCR addresses from factory logs, instantiate and add
+  // event listeners.
+  const deploymentBlock = Number(process.env.FACTORY_BLOCK_NUM) || 0
+
+  // Fetch logs by scanning the blockchain in batches of 4 months
+  // to avoid rate-limiting.
+  const blocksPerMinute = Math.floor(
+    60 / (Number(process.env.BLOCK_TIME_MILLISECONDS as string) / 1000)
+  )
+  const blocksPerRequest = blocksPerMinute * 60 * 24 * 30 * 4
+
+  // Fetch the addresses of TCRs deployed with this factory.
+  const logPromises = []
+  for (let fromBlock = deploymentBlock; ; ) {
+    logPromises.push(
+      provider.getLogs({
+        ...gtcrFactory.filters.NewGTCR(),
+        fromBlock: fromBlock,
+        toBlock: fromBlock + blocksPerRequest
+      })
+    )
+
+    if (fromBlock + blocksPerRequest >= currBlock) break
+    fromBlock += blocksPerRequest
+  }
+
+  // Concat results and instantiate TCRs.
+  const tcrs = (await Promise.all(logPromises))
+    .reduce((acc, curr) => acc.concat(curr), [])
+    .map(log => gtcrFactory.interface.parseLog(log).values._address)
+    .map(address => new ethers.Contract(address, _GeneralizedTCR.abi, provider))
+
+  // Add listeners for events emitted by the TCRs.
+  await Promise.all(
+    tcrs.map(tcr =>
+      addTCRListeners(
+        tcr
+      )
+    )
+  )
+
+  // Watch for new TCRs and add listeners.
+  gtcrFactory.on(gtcrFactory.filters.NewGTCR(), _address =>
+    addTCRListeners(
+      new ethers.Contract(_address, _GeneralizedTCR.abi, provider),
+    )
+  )
+
+  console.info()
+  console.info('Done. Watching for blockchain events.')
+})()

tsconfig.json

@@ -11,7 +11,8 @@
     "noFallthroughCasesInSwitch": true,
     "noImplicitAny": true,
     "noImplicitThis": true,
-    "strictNullChecks": true
+    "strictNullChecks": true,
+    "esModuleInterop": true,
   },
   "include": [
     "src/**/*"

utils/env-check.js

@@ -0,0 +1,21 @@
+// Web3
+if (!process.env.PROVIDER_URL) {
+  console.error(
+    'No web3 provider set. Please set the PROVIDER_URL environment variable'
+  )
+  process.exit(1)
+}
+
+if (!process.env.FACTORY_ADDRESS) {
+  console.error(
+    'No factory address set. Please set the FACTORY_ADDRESS environment variable'
+  )
+  process.exit(1)
+}
+
+if (!process.env.BLOCK_TIME_MILLISECONDS) {
+  console.error(
+    'Network block time not set. Please set the BLOCK_TIME_MILLISECONDS environment variable'
+  )
+  process.exit(1)
+}

yarn.lock

@@ -913,13 +913,13 @@ bignumber.js@^7.2.1:
   resolved "https://registry.yarnpkg.com/bignumber.js/-/bignumber.js-7.2.1.tgz#80c048759d826800807c4bfd521e50edbba57a5f"
   integrity sha512-S4XzBk5sMB+Rcb/LNcpzXr57VRTxgAvaAEDAl1AwRx27j00hT84O6OkteE7u8UB3NuaaygCRrEpqox4uDOrbdQ==
 
-"bignumber.js@git+https://github.com/debris/bignumber.js.git#94d7146671b9719e00a09c29b01a691bc85048c2":
+"bignumber.js@git+https://github.com/debris/bignumber.js#master":
   version "2.0.7"
-  resolved "git+https://github.com/debris/bignumber.js.git#94d7146671b9719e00a09c29b01a691bc85048c2"
+  resolved "git+https://github.com/debris/bignumber.js#c7a38de919ed75e6fb6ba38051986e294b328df9"
 
-"bignumber.js@git+https://github.com/debris/bignumber.js.git#master":
+"bignumber.js@git+https://github.com/debris/bignumber.js.git#94d7146671b9719e00a09c29b01a691bc85048c2":
   version "2.0.7"
-  resolved "git+https://github.com/debris/bignumber.js.git#c7a38de919ed75e6fb6ba38051986e294b328df9"
+  resolved "git+https://github.com/debris/bignumber.js.git#94d7146671b9719e00a09c29b01a691bc85048c2"
 
 binaryextensions@^2.2.0:
   version "2.2.0"