Implement zeroEx.exchange.subscribeAsync made sure to clean up subscriptions if user updates the provider

4 files changed, 91 insertions, 3 deletions

diff --git a/src/0x.js.ts b/src/0x.js.ts
index 967c81ed8..0cda7732d 100644
--- a/src/0x.js.ts
+++ b/src/0x.js.ts
@@ -115,9 +115,9 @@ export class ZeroEx {
     /**
      * Sets a new provider for the web3 instance used by 0x.js
      */
-    public setProvider(provider: Web3.Provider) {
+    public async setProviderAsync(provider: Web3.Provider) {
         this.web3Wrapper.setProvider(provider);
-        this.exchange.invalidateContractInstance();
+        await this.exchange.invalidateContractInstanceAsync();
         this.tokenRegistry.invalidateContractInstance();
         this.token.invalidateContractInstances();
     }
diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index f32cb88a6..b394edb06 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -1,5 +1,6 @@
 import * as _ from 'lodash';
 import * as BigNumber from 'bignumber.js';
+import promisify = require('es6-promisify');
 import {Web3Wrapper} from '../web3_wrapper';
 import {
     ECSignature,
@@ -11,8 +12,16 @@ import {
     OrderAddresses,
     SignedOrder,
     ContractEvent,
+    ZeroExError,
+    ExchangeEvents,
+    SubscriptionOpts,
+    IndexFilterValues,
+    CreateContractEvent,
+    ContractEventObj,
+    EventCallback,
 } from '../types';
 import {assert} from '../utils/assert';
+import {utils} from '../utils/utils';
 import {ContractWrapper} from './contract_wrapper';
 import * as ExchangeArtifacts from '../artifacts/Exchange.json';
 import {ecSignatureSchema} from '../schemas/ec_signature_schema';
@@ -32,12 +41,15 @@ export class ExchangeWrapper extends ContractWrapper {
         [ExchangeContractErrCodes.ERROR_FILL_BALANCE_ALLOWANCE]: ExchangeContractErrs.ORDER_BALANCE_ALLOWANCE_ERROR,
     };
     private exchangeContractIfExists?: ExchangeContract;
+    private exchangeLogEventObjs: ContractEventObj[];
     private tokenWrapper: TokenWrapper;
     constructor(web3Wrapper: Web3Wrapper, tokenWrapper: TokenWrapper) {
         super(web3Wrapper);
         this.tokenWrapper = tokenWrapper;
+        this.exchangeLogEventObjs = [];
     }
-    public invalidateContractInstance(): void {
+    public async invalidateContractInstanceAsync(): Promise<void> {
+        await this.stopWatchingExchangeLogEventsAsync();
         delete this.exchangeContractIfExists;
     }
     public async isValidSignatureAsync(dataHex: string, ecSignature: ECSignature,
@@ -159,6 +171,38 @@ export class ExchangeWrapper extends ContractWrapper {
         );
         this.throwErrorLogsAsErrors(response.logs);
     }
+    /**
+     * Subscribe to an event type emitted by the Exchange smart contract
+     */
+    public async subscribeAsync(eventName: ExchangeEvents, subscriptionOpts: SubscriptionOpts,
+                                indexFilterValues: IndexFilterValues, callback: EventCallback) {
+        const exchangeContract = await this.getExchangeContractAsync();
+        let createLogEvent: CreateContractEvent;
+        switch (eventName) {
+            case ExchangeEvents.LogFill:
+                createLogEvent = exchangeContract.LogFill;
+                break;
+            case ExchangeEvents.LogError:
+                createLogEvent = exchangeContract.LogError;
+                break;
+            case ExchangeEvents.LogCancel:
+                createLogEvent = exchangeContract.LogCancel;
+                break;
+            default:
+                utils.spawnSwitchErr('ExchangeEvents', eventName);
+                return;
+        }
+
+        const logEventObj: ContractEventObj = createLogEvent(indexFilterValues, subscriptionOpts);
+        logEventObj.watch(callback);
+        this.exchangeLogEventObjs.push(logEventObj);
+    }
+    private async stopWatchingExchangeLogEventsAsync() {
+        for (const logEventObj of this.exchangeLogEventObjs) {
+            await promisify(logEventObj.stopWatching, logEventObj)();
+        }
+        this.exchangeLogEventObjs = [];
+    }
     private async validateFillOrderAsync(signedOrder: SignedOrder, fillAmount: BigNumber.BigNumber,
                                          senderAddress: string) {
         if (fillAmount.eq(0)) {
diff --git a/src/types.ts b/src/types.ts
index 29f7e0ee4..c6ad68d3f 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -51,6 +51,22 @@ export interface ExchangeContract {
     };
 }
 
+export type EventCallbackAsync = (err: Error, event: ContractEvent) => Promise<void>;
+export type EventCallbackSync = (err: Error, event: ContractEvent) => void;
+export type EventCallback = EventCallbackSync|EventCallbackAsync;
+export interface ContractEventObj {
+    watch: (eventWatch: EventCallback) => void;
+    stopWatching: () => void;
+}
+export type CreateContractEvent = (indexFilterValues: IndexFilterValues,
+                                   subscriptionOpts: SubscriptionOpts) => ContractEventObj;
+export interface ExchangeContract {
+    isValidSignature: any;
+    LogFill: CreateContractEvent;
+    LogCancel: CreateContractEvent;
+    LogError: CreateContractEvent;
+}
+
 export interface TokenContract {
     balanceOf: {
         call: (address: string) => Promise<BigNumber.BigNumber>;
@@ -110,6 +126,13 @@ export interface ContractResponse {
 }
 
 export interface ContractEvent {
+    logIndex: number;
+    transactionIndex: number;
+    transactionHash: string;
+    blockHash: string;
+    blockNumber: number;
+    address: string;
+    type: string;
     event: string;
     args: any;
 }
@@ -151,3 +174,21 @@ export interface TxOpts {
 export interface TokenAddressBySymbol {
     [symbol: string]: string;
 }
+
+export const ExchangeEvents = strEnum([
+    'LogFill',
+    'LogCancel',
+    'LogError',
+]);
+export type ExchangeEvents = keyof typeof ExchangeEvents;
+
+export interface IndexFilterValues {
+    [index: string]: any;
+}
+
+export interface SubscriptionOpts {
+    fromBlock: string|number;
+    toBlock: string|number;
+}
+
+export type DoneCallback = (err?: Error) => void;
diff --git a/src/utils/utils.ts b/src/utils/utils.ts
index e6840a624..114b46f6c 100644
--- a/src/utils/utils.ts
+++ b/src/utils/utils.ts
@@ -22,4 +22,7 @@ export const utils = {
         const isValid = /^0x[0-9A-F]{64}$/i.test(orderHashHex);
         return isValid;
     },
+    spawnSwitchErr(name: string, value: any) {
+        return new Error(`Unexpected switch value: ${value} encountered for ${name}`);
+    },
 };