Merge pull request #1221 from 0xProject/feature/instant/fallback-provider

[instant] Ensure we always have a provider from initial state

1 files changed, 34 insertions, 0 deletions

diff --git a/packages/instant/src/util/provider_factory.ts b/packages/instant/src/util/provider_factory.ts
new file mode 100644
index 000000000..603f7674d
--- /dev/null
+++ b/packages/instant/src/util/provider_factory.ts
@@ -0,0 +1,34 @@
+import { EmptyWalletSubprovider, RPCSubprovider, Web3ProviderEngine } from '@0x/subproviders';
+import { Provider } from 'ethereum-types';
+import * as _ from 'lodash';
+
+import { BLOCK_POLLING_INTERVAL_MS, ETHEREUM_NODE_URL_BY_NETWORK } from '../constants';
+import { Maybe, Network } from '../types';
+
+export const providerFactory = {
+    getInjectedProviderIfExists: (): Maybe<Provider> => {
+        const injectedProviderIfExists = (window as any).ethereum;
+        if (!_.isUndefined(injectedProviderIfExists)) {
+            return injectedProviderIfExists;
+        }
+        const injectedWeb3IfExists = (window as any).web3;
+        if (!_.isUndefined(injectedWeb3IfExists) && !_.isUndefined(injectedWeb3IfExists.currentProvider)) {
+            return injectedWeb3IfExists.currentProvider;
+        }
+        return undefined;
+    },
+    getFallbackNoSigningProvider: (network: Network): Provider => {
+        const providerEngine = new Web3ProviderEngine({
+            pollingInterval: BLOCK_POLLING_INTERVAL_MS,
+        });
+        // Intercept calls to `eth_accounts` and always return empty
+        providerEngine.addProvider(new EmptyWalletSubprovider());
+        // Construct an RPC subprovider, all data based requests will be sent via the RPCSubprovider
+        // TODO(bmillman): make this more resilient to infura failures
+        const rpcUrl = ETHEREUM_NODE_URL_BY_NETWORK[network];
+        providerEngine.addProvider(new RPCSubprovider(rpcUrl));
+        // // Start the Provider Engine
+        providerEngine.start();
+        return providerEngine;
+    },
+};