Implement wallet_switchEthereumChain (#2111)

* Implement wallet_switchEthereumChain

* Run prettier

---------

Co-authored-by: Chase Fleming <1666730+chasefleming@users.noreply.github.com>

packages/fcl-ethereum-provider/src/network/network-manager.ts

@@ -11,7 +11,7 @@ import {
   switchMap,
 } from "../util/observable"
 import * as fcl from "@onflow/fcl"
-import {AddEthereumChainParams} from "../types/eth"
+import {AddEthereumChainParams, SwitchEthereumChainParams} from "../types/eth"
 
 export type ChainIdStore = {
   isLoading: boolean
@@ -86,9 +86,24 @@ export class NetworkManager {
    * No-op implementation for wallet_addEthereumChain.
    * Since FCL does support dynamic chain additions.
    */
-  public async wallet_addEthereumChain(
-    _chainConfig: AddEthereumChainParams
-  ): Promise<null> {
+  public async addChain(_chainConfig: AddEthereumChainParams): Promise<null> {
+    return null
+  }
+
+  public async switchChain(params: SwitchEthereumChainParams): Promise<null> {
+    const activeChainId = await this.getChainId()
+    if (activeChainId === null) {
+      throw new Error("No active chain configured.")
+    }
+
+    // Convert the chainId from hex (e.g., "0x64") to a number.
+    const requestedChainId = parseInt(params.chainId, 16)
+
+    if (requestedChainId !== activeChainId) {
+      throw new Error(
+        "Network switch error: The requested chain ID does not match the currently configured network."
+      )
+    }
     return null
   }
 }

packages/fcl-ethereum-provider/src/rpc/rpc-processor.ts

@@ -9,6 +9,7 @@ import {
   AddEthereumChainParams,
   PersonalSignParams,
   SignTypedDataParams,
+  SwitchEthereumChainParams,
   TypedData,
 } from "../types/eth"
 import {signTypedData} from "./handlers/eth-signtypeddata"
@@ -73,7 +74,16 @@ export class RpcProcessor {
         }
         const chainConfig = params[0] as AddEthereumChainParams
 
-        return await this.networkManager.wallet_addEthereumChain(chainConfig)
+        return await this.networkManager.addChain(chainConfig)
+      case "wallet_switchEthereumChain":
+        // Expect params to be an array with one object.
+        if (!params || !Array.isArray(params) || !params[0]) {
+          throw new Error(
+            "wallet_switchEthereumChain requires an array with a chain configuration object."
+          )
+        }
+        const switchParams = params[0] as SwitchEthereumChainParams
+        return await this.networkManager.switchChain(switchParams)
       default:
         return await this.gateway.request({
           chainId,

packages/fcl-ethereum-provider/src/types/eth.ts

@@ -39,3 +39,7 @@ export interface AddEthereumChainParams {
   blockExplorerUrls?: string[]
   iconUrls?: string[]
 }
+
+export interface SwitchEthereumChainParams {
+  chainId: string // Hex string, e.g., "0x64"
+}