2 files changed, 57 insertions, 34 deletions

diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index 57a116aea..722910a61 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -34,6 +34,7 @@ import {
 } from '../types';
 import {assert} from '../utils/assert';
 import {utils} from '../utils/utils';
+import {eventUtils} from '../utils/event_utils';
 import {ContractWrapper} from './contract_wrapper';
 import {ProxyWrapper} from './proxy_wrapper';
 import {ExchangeArtifactsByName} from '../exchange_artifacts_by_name';
@@ -601,7 +602,7 @@ export class ExchangeWrapper extends ContractWrapper {
         }
 
         const logEventObj: ContractEventObj = createLogEvent(indexFilterValues, subscriptionOpts);
-        const eventEmitter = this._wrapEventEmitter(logEventObj);
+        const eventEmitter = eventUtils.wrapEventEmitter(logEventObj);
         this._exchangeLogEventEmitters.push(eventEmitter);
         return eventEmitter;
     }
@@ -655,37 +656,6 @@ export class ExchangeWrapper extends ContractWrapper {
         const isAuthorized = await this._proxyWrapper.isAuthorizedAsync(exchangeContractAddress);
         return isAuthorized;
     }
-    private _wrapEventEmitter(event: ContractEventObj): ContractEventEmitter {
-        const watch = (eventCallback: EventCallback) => {
-            const bignumberWrappingEventCallback = this._getBigNumberWrappingEventCallback(eventCallback);
-            event.watch(bignumberWrappingEventCallback);
-        };
-        const zeroExEvent = {
-            watch,
-            stopWatchingAsync: async () => {
-                await promisify(event.stopWatching, event)();
-            },
-        };
-        return zeroExEvent;
-    }
-    private _getBigNumberWrappingEventCallback(eventCallback: EventCallback): EventCallback {
-        const bignumberWrappingEventCallback = (err: Error, event: ContractEvent) => {
-            if (_.isNull(err)) {
-                const wrapIfBigNumber = (value: ContractEventArg): ContractEventArg => {
-                    // HACK: The old version of BigNumber used by Web3@0.19.0 does not support the `isBigNumber`
-                    // and checking for a BigNumber instance using `instanceof` does not work either. We therefore
-                    // compare the constructor functions of the possible BigNumber instance and the BigNumber used by
-                    // Web3.
-                    const web3BigNumber = (Web3.prototype as any).BigNumber;
-                    const isWeb3BigNumber = web3BigNumber.toString() === value.constructor.toString();
-                    return isWeb3BigNumber ?  new BigNumber(value) : value;
-                };
-                event.args = _.mapValues(event.args, wrapIfBigNumber);
-            }
-            eventCallback(err, event);
-        };
-        return bignumberWrappingEventCallback;
-    }
     private async _isValidSignatureUsingContractCallAsync(dataHex: string, ecSignature: ECSignature,
                                                           signerAddressHex: string,
                                                           exchangeContractAddress: string): Promise<boolean> {
diff --git a/src/contract_wrappers/token_wrapper.ts b/src/contract_wrappers/token_wrapper.ts
index e34c624ab..d60843cdb 100644
--- a/src/contract_wrappers/token_wrapper.ts
+++ b/src/contract_wrappers/token_wrapper.ts
@@ -2,11 +2,22 @@ import * as _ from 'lodash';
 import * as BigNumber from 'bignumber.js';
 import {Web3Wrapper} from '../web3_wrapper';
 import {assert} from '../utils/assert';
+import {utils} from '../utils/utils';
+import {eventUtils} from '../utils/event_utils';
 import {constants} from '../utils/constants';
 import {ContractWrapper} from './contract_wrapper';
 import * as TokenArtifacts from '../artifacts/Token.json';
 import * as ProxyArtifacts from '../artifacts/Proxy.json';
-import {TokenContract, ZeroExError} from '../types';
+import {
+    TokenContract,
+    ZeroExError,
+    TokenEvents,
+    IndexedFilterValues,
+    SubscriptionOpts,
+    CreateContractEvent,
+    ContractEventEmitter,
+    ContractEventObj,
+} from '../types';
 
 const ALLOWANCE_TO_ZERO_GAS_AMOUNT = 45730;
 
@@ -17,11 +28,14 @@ const ALLOWANCE_TO_ZERO_GAS_AMOUNT = 45730;
  */
 export class TokenWrapper extends ContractWrapper {
     private _tokenContractsByAddress: {[address: string]: TokenContract};
+    private _tokenLogEventEmitters: ContractEventEmitter[];
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
         this._tokenContractsByAddress = {};
+        this._tokenLogEventEmitters = [];
     }
-    public invalidateContractInstances() {
+    public async invalidateContractInstancesAsync(): Promise<void> {
+        await this.stopWatchingAllEventsAsync();
         this._tokenContractsByAddress = {};
     }
     /**
@@ -178,6 +192,45 @@ export class TokenWrapper extends ContractWrapper {
             from: senderAddress,
         });
     }
+    /**
+     * Subscribe to an event type emitted by the Token smart contract
+     * @param   tokenAddress        The hex encoded contract Ethereum address where the ERC20 token is deployed.
+     * @param   eventName           The token contract event you would like to subscribe to.
+     * @param   subscriptionOpts    Subscriptions options that let you configure the subscription.
+     * @param   indexFilterValues   An object where the keys are indexed args returned by the event and
+     *                              the value is the value you are interested in. E.g `{maker: aUserAddressHex}`
+     * @return                      ContractEventEmitter object
+     */
+    public async subscribeAsync(tokenAddress: string, eventName: TokenEvents, subscriptionOpts: SubscriptionOpts,
+                                indexFilterValues: IndexedFilterValues):
+                                Promise<ContractEventEmitter> {
+        const tokenContract = await this._getTokenContractAsync(tokenAddress);
+        let createLogEvent: CreateContractEvent;
+        switch (eventName) {
+            case TokenEvents.Approval:
+                createLogEvent = tokenContract.Approval;
+                break;
+            case TokenEvents.Transfer:
+                createLogEvent = tokenContract.Transfer;
+                break;
+            default:
+                throw utils.spawnSwitchErr('TokenEvents', eventName);
+        }
+
+        const logEventObj: ContractEventObj = createLogEvent(indexFilterValues, subscriptionOpts);
+        const eventEmitter = eventUtils.wrapEventEmitter(logEventObj);
+        this._tokenLogEventEmitters.push(eventEmitter);
+        return eventEmitter;
+    }
+    /**
+     * Stops watching for all token events
+     */
+    public async stopWatchingAllEventsAsync(): Promise<void> {
+        const stopWatchingPromises = _.map(this._tokenLogEventEmitters,
+                                           logEventObj => logEventObj.stopWatchingAsync());
+        await Promise.all(stopWatchingPromises);
+        this._tokenLogEventEmitters = [];
+    }
     private async _getTokenContractAsync(tokenAddress: string): Promise<TokenContract> {
         let tokenContract = this._tokenContractsByAddress[tokenAddress];
         if (!_.isUndefined(tokenContract)) {