From 79375a55955cae888e44044f0de376447927bec1 Mon Sep 17 00:00:00 2001
From: Moody Salem <moodysalem@users.noreply.github.com>
Date: Fri, 9 Oct 2020 10:18:57 -0500
Subject: [PATCH] Batch JSON RPC calls using an RPC provider from Uniswap

This is taken from https://github.com/Uniswap/uniswap-interface/blob/master/src/connectors/NetworkConnector.ts#L31
---
 src/api/EthereumAccountManager.ts | 132 +++++++++++++++++++++++++++++-
 1 file changed, 131 insertions(+), 1 deletion(-)

diff --git a/src/api/EthereumAccountManager.ts b/src/api/EthereumAccountManager.ts
index 42840f41..b1586abf 100644
--- a/src/api/EthereumAccountManager.ts
+++ b/src/api/EthereumAccountManager.ts
@@ -4,6 +4,136 @@ import { providers, Contract, Wallet, utils } from 'ethers';
 import { EthAddress } from '../_types/global/GlobalTypes';
 import { address } from '../utils/CheckedTypeUtils';
 
+// taken from ethers.js, compatible interface with web3 provider
+type AsyncSendable = {
+  isMetaMask?: boolean
+  host?: string
+  path?: string
+  sendAsync?: (request: any, callback: (error: any, response: any) => void) => void
+  send?: (request: any, callback: (error: any, response: any) => void) => void
+}
+
+class RequestError extends Error {
+  constructor(message: string, public code: number, public data?: unknown) {
+    super(message)
+  }
+}
+
+interface BatchItem {
+  request: { jsonrpc: '2.0'; id: number; method: string; params: unknown }
+  resolve: (result: any) => void
+  reject: (error: Error) => void
+}
+
+class MiniRpcProvider implements AsyncSendable {
+  public readonly isMetaMask: false = false
+  public readonly chainId: number
+  public readonly url: string
+  public readonly host: string
+  public readonly path: string
+  public readonly batchWaitTimeMs: number
+
+  private nextId = 1
+  private batchTimeoutId: ReturnType<typeof setTimeout> | null = null
+  private batch: BatchItem[] = []
+
+  constructor(chainId: number, url: string, batchWaitTimeMs?: number) {
+    this.chainId = chainId
+    this.url = url
+    const parsed = new URL(url)
+    this.host = parsed.host
+    this.path = parsed.pathname
+    // how long to wait to batch calls
+    this.batchWaitTimeMs = batchWaitTimeMs ?? 50
+  }
+
+  public readonly clearBatch = async () => {
+    console.debug('Clearing batch', this.batch)
+    const batch = this.batch
+    this.batch = []
+    this.batchTimeoutId = null
+    let response: Response
+    try {
+      response = await fetch(this.url, {
+        method: 'POST',
+        headers: { 'content-type': 'application/json', accept: 'application/json' },
+        body: JSON.stringify(batch.map(item => item.request))
+      })
+    } catch (error) {
+      batch.forEach(({ reject }) => reject(new Error('Failed to send batch call')))
+      return
+    }
+
+    if (!response.ok) {
+      batch.forEach(({ reject }) => reject(new RequestError(`${response.status}: ${response.statusText}`, -32000)))
+      return
+    }
+
+    let json
+    try {
+      json = await response.json()
+    } catch (error) {
+      batch.forEach(({ reject }) => reject(new Error('Failed to parse JSON response')))
+      return
+    }
+    const byKey = batch.reduce<{ [id: number]: BatchItem }>((memo, current) => {
+      memo[current.request.id] = current
+      return memo
+    }, {})
+    for (const result of json) {
+      const {
+        resolve,
+        reject,
+        request: { method }
+      } = byKey[result.id]
+      if (resolve && reject) {
+        if ('error' in result) {
+          reject(new RequestError(result?.error?.message, result?.error?.code, result?.error?.data))
+        } else if ('result' in result) {
+          resolve(result.result)
+        } else {
+          reject(new RequestError(`Received unexpected JSON-RPC response to ${method} request.`, -32000, result))
+        }
+      }
+    }
+  }
+
+  public readonly sendAsync = (
+    request: { jsonrpc: '2.0'; id: number | string | null; method: string; params?: unknown[] | object },
+    callback: (error: any, response: any) => void
+  ): void => {
+    this.request(request.method, request.params)
+      .then(result => callback(null, { jsonrpc: '2.0', id: request.id, result }))
+      .catch(error => callback(error, null))
+  }
+
+  public readonly request = async (
+    method: string | { method: string; params: unknown[] },
+    params?: unknown[] | object
+  ): Promise<unknown> => {
+    if (typeof method !== 'string') {
+      return this.request(method.method, method.params)
+    }
+    if (method === 'eth_chainId') {
+      return `0x${this.chainId.toString(16)}`
+    }
+    const promise = new Promise((resolve, reject) => {
+      this.batch.push({
+        request: {
+          jsonrpc: '2.0',
+          id: this.nextId++,
+          method,
+          params
+        },
+        resolve,
+        reject
+      })
+    })
+    this.batchTimeoutId = this.batchTimeoutId ?? setTimeout(this.clearBatch, this.batchWaitTimeMs)
+    return promise
+  }
+}
+
 class EthereumAccountManager {
   static instance: EthereumAccountManager | null = null;
 
@@ -14,7 +144,7 @@ class EthereumAccountManager {
   private constructor() {
     const isProd = process.env.NODE_ENV === 'production';
     const url = isProd ? 'https://rpc.xdaichain.com/' : 'http://localhost:8545';
-    this.provider = new providers.JsonRpcProvider(url);
+    this.provider = new providers.Web3Provider((new MiniRpcProvider(100, url, 100)) as providers.ExternalProvider);
     this.signer = null;
     this.knownAddresses = [];
     const knownAddressesStr = localStorage.getItem('KNOWN_ADDRESSES');