Refactor to compute GasPrices differently

src/blockchain.ts

@@ -1,6 +1,5 @@
 import 'dotenv/config.js';
 import { WebSocketProvider, formatUnits } from 'ethers';
-import { sortBy } from 'lodash';
 import { Observable, throwError } from 'rxjs';
 import { catchError, map, scan, retry } from 'rxjs/operators';
 
@@ -10,47 +9,51 @@ const rpcUrl = process.env.RPC_URL || "wss://ropsten.infura.io/ws/v3/YOUR_INFURA
 
 const provider = new WebSocketProvider(rpcUrl);
 
-const blockGasPricesObservable = new Observable<GasPrices>((observer) => {
+const blockBaseFeePerGasObservable$ = new Observable<number>((observer) => {
   provider.on('block', async (blockNumber) => {
     try {
-      const block = await provider.getBlock(blockNumber, true);
+      const { baseFeePerGas } = await provider.getBlock(blockNumber, true) || {};
 
-      if (!block) throw new Error(`Error fetching block! ${blockNumber}`);
-
-      const gasPrices = sortBy(block.prefetchedTransactions, ['gasPrice']).map(x => x.gasPrice);
-      const fast = Number(formatUnits(gasPrices[Math.floor(gasPrices.length * 0.9)], "gwei"));
-      const average = Number(formatUnits(gasPrices[Math.floor(gasPrices.length / 2)], "gwei"));
-      const slow = Number(formatUnits(gasPrices[Math.floor(gasPrices.length * 0.05)], "gwei"));
+      if (!baseFeePerGas) throw new Error(`Error fetching block! ${blockNumber}`);
 
       // Log averages every 10 blocks
-      if (blockNumber % 10 == 0) console.log(`Found new block data for ${blockNumber}!
-      Gas price spreads: ⚡ ${fast.toFixed(2)} ⦚⦚ 🚶 ${average.toFixed(2)} ⦚⦚ 🐢 ${slow.toFixed(2)} Gwei`)
+      if (blockNumber % 10 == 0) console.log(
+        `Found new block data for ${blockNumber}! Gas price: 🐢 ${Number(formatUnits(baseFeePerGas, "gwei")).toFixed(2)} Gwei`
+      )
 
-      observer.next({ fast, average, slow } as GasPrices);
+      observer.next(Number(formatUnits(baseFeePerGas, "gwei")));
     } catch (error) {
       observer.error(`Error fetching block! ${error}`);
     }
   });
 });
 
-const averageGasPricesObservable = blockGasPricesObservable.pipe(
-  scan((acc, curr) => [...acc.slice(-19), curr], [] as GasPrices[]),
-  map((blocks) => {
-    const { fast, average, slow } = blocks
-      .reduce((sum, block) =>
-        ({ // Find sums
-          fast: sum.fast + block.fast,
-          average: sum.average + block.average,
-          slow: sum.slow + block.slow
-        }), { fast: 0, average: 0, slow: 0 } as GasPrices);
-    return { // Then average them
-      fast: Math.round(fast / blocks.length),
-      average: Math.round(average / blocks.length),
-      slow: Math.round(slow / blocks.length),
-    } as GasPrices;
+const baseGasPricesObservable$ = blockBaseFeePerGasObservable$.pipe(
+  scan<number, GasPrices>(
+    (acc: GasPrices, curr: number): GasPrices => {
+      // Keep only the 20 latest values
+      const values: number[] = acc.values ? [...acc.values.slice(-19), curr] : [curr];
+
+      const fast: number = Math.max(...values);
+      const slow: number = Math.min(...values);
+      const sum: number = values.reduce((a, b) => a + b, 0);
+      const average: number = sum / values.length;
+
+      return { values, fast, slow, average };
+    },
+    { values: [], fast: -Infinity, slow: Infinity, average: NaN } // Initial value
+  ),
+  // Only emit the computed prices
+  map<GasPrices, GasPrices>((computedGasPrices: GasPrices): GasPrices => {
+    const { fast, average, slow } = computedGasPrices;
+    return {
+      fast: Math.round(fast),
+      average: Math.round(average),
+      slow: Math.round(slow)
+    };
   }),
   catchError(err => throwError(() => new Error(err))),
   retry(2)
 );
 
-export { averageGasPricesObservable };
+export { baseGasPricesObservable$ };

src/index.ts

@@ -9,7 +9,7 @@ import fs from 'node:fs';
 import path from 'node:path';
 import { ActivityType, GatewayIntentBits } from 'discord.js';
 
-import { averageGasPricesObservable } from './blockchain';
+import { baseGasPricesObservable$ } from './blockchain';
 import { deployCommands } from './deploy';
 import { DiscordClient } from './discordClient';
 import { createGasAlertChecker } from './gasAlertChecker';
@@ -76,7 +76,7 @@ client.login(token)
   })
   .then(() => {
     // Start listening to blockchain
-    averageGasPricesObservable.subscribe({
+    baseGasPricesObservable$.subscribe({
       next: async (averageGasPrices) => {
         setDiscordStatus(averageGasPrices);
         await redisClient.set('current-prices', JSON.stringify(averageGasPrices))

types/gasPrices.d.ts

@@ -2,4 +2,5 @@ export interface GasPrices {
   fast: number;
   average: number;
   slow: number;
+  values?: number[];
 }