bmon: Report empty findings above a given threshold

bmon: Fix linter issues

packages/balance-monitor/.env.example

-export CHAINID=
 export L1_RPC_URL=
 
 # Prepopulated with test values.
@@ -9,4 +8,3 @@ export SEQUENCER_DANGER_THRESHOLD=100
 export PROPOSER_ADDRESS=0xacdc
 export PROPOSER_WARNING_THRESHOLD=2000
 export PROPOSER_DANGER_THRESHOLD=200
-

packages/balance-monitor/package.json

@@ -29,11 +29,12 @@
     "forta-agent": "^0.1.1"
   },
   "devDependencies": {
-    "@types/jest": "^26.0.23",
+    "@types/chai": "^4.2.18",
+    "@types/mocha": "^8.2.2",
     "@types/nodemon": "^1.19.0",
-    "jest": "^27.0.6",
+    "chai": "^4.3.4",
     "nodemon": "^2.0.8",
-    "ts-jest": "^27.0.3",
+    "ts-mocha": "^10.0.0",
     "typescript": "^4.3.4"
   }
 }

packages/balance-monitor/src/agent.spec.ts

+import { HandleBlock, createBlockEvent } from 'forta-agent'
+import { BigNumber, utils } from 'ethers'
+import { expect } from 'chai'
+
+import agent from './agent'
+
+describe('minimum balance agent', async () => {
+  let handleBlock: HandleBlock
+  let mockEthersProvider
+  const blockEvent = createBlockEvent({
+    block: { hash: '0xa', number: 1 } as any,
+  })
+
+  // A function which returns a mock provider to give us values based on the case we want
+  // to test.
+  const mockEthersProviderByCase = (severity: string) => {
+    switch (severity) {
+      case 'safe':
+        return {
+          getBalance: async (addr: string): Promise<BigNumber> => {
+            if (addr === '0xabba') {
+              return utils.parseEther('1001')
+            }
+            if (addr === '0xacdc') {
+              return utils.parseEther('2001')
+            }
+          },
+        } as any
+      default:
+        break
+    }
+  }
+
+  before(() => {
+    handleBlock = agent.provideHandleBlock(mockEthersProvider)
+  })
+
+  describe('handleBlock', async () => {
+    it('returns empty findings if balance is above threshold', async () => {
+      mockEthersProvider = mockEthersProviderByCase('safe')
+      handleBlock = agent.provideHandleBlock(mockEthersProvider)
+      const findings = await handleBlock(blockEvent)
+
+      expect(findings).to.deep.equal([])
+    })
+  })
+})

packages/balance-monitor/src/agent.ts

+import { BlockEvent, Finding, HandleBlock } from 'forta-agent'
+import { BigNumber, providers } from 'ethers'
+
+type AccountAlert = {
+  name: string
+  address: string
+  thresholds: {
+    warning: BigNumber
+    danger: BigNumber
+  }
+}
+
+export const accounts: AccountAlert[] = [
+  {
+    name: 'Sequencer',
+    address: process.env.SEQUENCER_ADDRESS,
+    thresholds: {
+      warning: BigNumber.from(process.env.SEQUENCER_WARNING_THRESHOLD),
+      danger: BigNumber.from(process.env.SEQUENCER_DANGER_THRESHOLD),
+    },
+  },
+  {
+    name: 'Proposer',
+    address: process.env.PROPOSER_ADDRESS,
+    thresholds: {
+      warning: BigNumber.from(process.env.PROPOSER_WARNING_THRESHOLD),
+      danger: BigNumber.from(process.env.PROPOSER_DANGER_THRESHOLD),
+    },
+  },
+]
+
+const provideHandleBlock = (
+  provider: providers.JsonRpcProvider
+): HandleBlock => {
+  return async (blockEvent: BlockEvent) => {
+    // report finding if specified account balance falls below threshold
+    const findings: Finding[] = []
+
+    // iterate over accounts with the index
+    for (const [idx, account] of accounts.entries()) {
+      const accountBalance = BigNumber.from(
+        (
+          await provider.getBalance(account.address, blockEvent.blockNumber)
+        ).toString()
+      )
+      if (accountBalance.gte(account.thresholds.warning)) {
+        // return if this is the last account
+        if (idx === accounts.length - 1) {
+          return findings
+        } else {
+          continue
+        }
+      }
+    }
+
+    // todo: Add to the findings array when balances are below the threshold
+
+    return findings
+  }
+}
+
+const l1Provider = new providers.JsonRpcProvider(process.env.L1_RPC_URL)
+
+export default {
+  provideHandleBlock,
+  handleBlock: provideHandleBlock(l1Provider),
+}