6 files changed, 134 insertions, 0 deletions
diff --git a/packages/subproviders/src/globals.d.ts b/packages/subproviders/src/globals.d.ts
index 53457fa24..6f344dcd3 100644
--- a/packages/subproviders/src/globals.d.ts
+++ b/packages/subproviders/src/globals.d.ts
@@ -13,7 +13,9 @@ declare module 'ethereumjs-tx' {
         public r: Buffer;
         public s: Buffer;
         public v: Buffer;
+        public nonce: Buffer;
         public serialize(): Buffer;
+        public getSenderAddress(): Buffer;
         constructor(txParams: any);
     }
     export = EthereumTx;
@@ -97,6 +99,24 @@ declare module 'web3-provider-engine' {
     }
     export = Web3ProviderEngine;
 }
+declare module 'web3-provider-engine/util/rpc-cache-utils' {
+    class ProviderEngineRpcUtils {
+        public static blockTagForPayload(payload: any): string | null;
+    }
+    export = ProviderEngineRpcUtils;
+}
+declare module 'web3-provider-engine/subproviders/fixture' {
+    import * as Web3 from 'web3';
+    class FixtureSubprovider {
+        constructor(staticResponses: any);
+        public handleRequest(
+            payload: Web3.JSONRPCRequestPayload,
+            next: () => void,
+            end: (err: Error | null, data?: any) => void,
+        ): void;
+    }
+    export = FixtureSubprovider;
+}
 
 // hdkey declarations
 declare module 'hdkey' {
diff --git a/packages/subproviders/src/index.ts b/packages/subproviders/src/index.ts
index 720c4362f..4b3be4efd 100644
--- a/packages/subproviders/src/index.ts
+++ b/packages/subproviders/src/index.ts
@@ -9,6 +9,7 @@ import { LedgerEthereumClient } from './types';
 export { InjectedWeb3Subprovider } from './subproviders/injected_web3';
 export { RedundantRPCSubprovider } from './subproviders/redundant_rpc';
 export { LedgerSubprovider } from './subproviders/ledger';
+export { NonceTrackerSubprovider } from './subproviders/nonce_tracker';
 export { ECSignature, LedgerWalletSubprovider, LedgerCommunicationClient } from './types';
 
 /**
diff --git a/packages/subproviders/src/subproviders/ledger.ts b/packages/subproviders/src/subproviders/ledger.ts
index 7267a793e..5966a88bb 100644
--- a/packages/subproviders/src/subproviders/ledger.ts
+++ b/packages/subproviders/src/subproviders/ledger.ts
@@ -60,6 +60,8 @@ export class LedgerSubprovider extends Subprovider {
     public setPathIndex(pathIndex: number) {
         this._derivationPathIndex = pathIndex;
     }
+    // Required to implement this public interface which doesn't conform to our linting rule.
+    // tslint:disable-next-line:async-suffix
     public async handleRequest(
         payload: Web3.JSONRPCRequestPayload,
         next: () => void,
diff --git a/packages/subproviders/src/subproviders/nonce_tracker.ts b/packages/subproviders/src/subproviders/nonce_tracker.ts
new file mode 100644
index 000000000..2f94ea581
--- /dev/null
+++ b/packages/subproviders/src/subproviders/nonce_tracker.ts
@@ -0,0 +1,97 @@
+import * as _ from 'lodash';
+
+import EthereumTx = require('ethereumjs-tx');
+import ethUtil = require('ethereumjs-util');
+import providerEngineUtils = require('web3-provider-engine/util/rpc-cache-utils');
+
+import {
+    BlockParamLiteral,
+    ErrorCallback,
+    JSONRPCPayload,
+    NonceSubproviderErrors,
+    OptionalNextCallback,
+} from '../types';
+
+import { Subprovider } from './subprovider';
+
+const NONCE_TOO_LOW_ERROR_MESSAGE = 'Transaction nonce is too low';
+export class NonceTrackerSubprovider extends Subprovider {
+    private _nonceCache: { [address: string]: string } = {};
+    private static _reconstructTransaction(payload: JSONRPCPayload): EthereumTx {
+        const raw = payload.params[0];
+        if (_.isUndefined(raw)) {
+            throw new Error(NonceSubproviderErrors.EmptyParametersFound);
+        }
+        const rawData = ethUtil.toBuffer(raw);
+        const transaction = new EthereumTx(rawData);
+        return transaction;
+    }
+    private static _determineAddress(payload: JSONRPCPayload): string {
+        let address: string;
+        switch (payload.method) {
+            case 'eth_getTransactionCount':
+                address = payload.params[0].toLowerCase();
+                return address;
+            case 'eth_sendRawTransaction':
+                const transaction = NonceTrackerSubprovider._reconstructTransaction(payload);
+                address = `0x${transaction.getSenderAddress().toString('hex')}`.toLowerCase();
+                return address;
+            default:
+                throw new Error(NonceSubproviderErrors.CannotDetermineAddressFromPayload);
+        }
+    }
+    // Required to implement this public interface which doesn't conform to our linting rule.
+    // tslint:disable-next-line:async-suffix
+    public async handleRequest(payload: JSONRPCPayload, next: OptionalNextCallback, end: ErrorCallback): Promise<void> {
+        switch (payload.method) {
+            case 'eth_getTransactionCount':
+                const requestDefaultBlock = providerEngineUtils.blockTagForPayload(payload);
+                if (requestDefaultBlock === BlockParamLiteral.Pending) {
+                    const address = NonceTrackerSubprovider._determineAddress(payload);
+                    const cachedResult = this._nonceCache[address];
+                    if (!_.isUndefined(cachedResult)) {
+                        return end(null, cachedResult);
+                    } else {
+                        return next((requestError: Error | null, requestResult: any, cb: any) => {
+                            if (_.isNull(requestError)) {
+                                this._nonceCache[address] = requestResult as string;
+                            }
+                            cb();
+                        });
+                    }
+                } else {
+                    return next();
+                }
+            case 'eth_sendRawTransaction':
+                return next((sendTransactionError: Error | null, txResult: any, cb: any) => {
+                    if (_.isNull(sendTransactionError)) {
+                        this._handleSuccessfulTransaction(payload);
+                    } else {
+                        this._handleSendTransactionError(payload, sendTransactionError);
+                    }
+                    cb();
+                });
+            default:
+                return next();
+        }
+    }
+    private _handleSuccessfulTransaction(payload: JSONRPCPayload): void {
+        const address = NonceTrackerSubprovider._determineAddress(payload);
+        const transaction = NonceTrackerSubprovider._reconstructTransaction(payload);
+        // Increment the nonce from the previous successfully submitted transaction
+        let nonce = ethUtil.bufferToInt(transaction.nonce);
+        nonce++;
+        let nextHexNonce = nonce.toString(16);
+        if (nextHexNonce.length % 2) {
+            nextHexNonce = `0${nextHexNonce}`;
+        }
+        nextHexNonce = `0x${nextHexNonce}`;
+        this._nonceCache[address] = nextHexNonce;
+    }
+    private _handleSendTransactionError(payload: JSONRPCPayload, err: Error): void {
+        const address = NonceTrackerSubprovider._determineAddress(payload);
+        if (this._nonceCache[address] && _.includes(err.message, NONCE_TOO_LOW_ERROR_MESSAGE)) {
+            delete this._nonceCache[address];
+        }
+    }
+}
diff --git a/packages/subproviders/src/subproviders/redundant_rpc.ts b/packages/subproviders/src/subproviders/redundant_rpc.ts
index a3cb463a8..5a94f93d7 100644
--- a/packages/subproviders/src/subproviders/redundant_rpc.ts
+++ b/packages/subproviders/src/subproviders/redundant_rpc.ts
@@ -35,6 +35,7 @@ export class RedundantRPCSubprovider extends Subprovider {
             });
         });
     }
+    // Required to implement this public interface which doesn't conform to our linting rule.
     // tslint:disable-next-line:async-suffix
     public async handleRequest(
         payload: JSONRPCPayload,
diff --git a/packages/subproviders/src/types.ts b/packages/subproviders/src/types.ts
index 3db8be943..86b118767 100644
--- a/packages/subproviders/src/types.ts
+++ b/packages/subproviders/src/types.ts
@@ -112,3 +112,16 @@ export enum LedgerSubproviderErrors {
     SenderInvalidOrNotSupplied = 'SENDER_INVALID_OR_NOT_SUPPLIED',
     MultipleOpenConnectionsDisallowed = 'MULTIPLE_OPEN_CONNECTIONS_DISALLOWED',
 }
+
+export enum NonceSubproviderErrors {
+    EmptyParametersFound = 'EMPTY_PARAMETERS_FOUND',
+    CannotDetermineAddressFromPayload = 'CANNOT_DETERMINE_ADDRESS_FROM_PAYLOAD',
+}
+
+// Re-defined BlockParamLiteral here, rather than import it from 0x.js.
+export enum BlockParamLiteral {
+    Pending = 'pending',
+}
+
+export type OptionalNextCallback = (callback?: (err: Error | null, result: any, cb: any) => void) => void;
+export type ErrorCallback = (err: Error | null, data?: any) => void;