4 files changed, 131 insertions, 0 deletions
diff --git a/src/0x.js.ts b/src/0x.js.ts
index 47b6679eb..97eb4d126 100644
--- a/src/0x.js.ts
+++ b/src/0x.js.ts
@@ -13,6 +13,7 @@ import compareVersions = require('compare-versions');
 import {ExchangeWrapper} from './contract_wrappers/exchange_wrapper';
 import {TokenRegistryWrapper} from './contract_wrappers/token_registry_wrapper';
 import {ecSignatureSchema} from './schemas/ec_signature_schema';
+import {TokenWrapper} from './contract_wrappers/token_wrapper';
 import {SolidityTypes, ECSignature, ZeroExError} from './types';
 import {Order} from './types';
 import {orderSchema} from "./schemas/signed_order_schema";
@@ -22,6 +23,7 @@ const MAX_DIGITS_IN_UNSIGNED_256_INT = 78;
 export class ZeroEx {
     public exchange: ExchangeWrapper;
     public tokenRegistry: TokenRegistryWrapper;
+    public token: TokenWrapper;
     private web3Wrapper: Web3Wrapper;
     /**
      * Computes the orderHash given the order parameters and returns it as a hex encoded string.
@@ -122,6 +124,7 @@ export class ZeroEx {
         this.web3Wrapper = new Web3Wrapper(web3);
         this.exchange = new ExchangeWrapper(this.web3Wrapper);
         this.tokenRegistry = new TokenRegistryWrapper(this.web3Wrapper);
+        this.token = new TokenWrapper(this.web3Wrapper);
     }
     /**
      * Sets a new provider for the web3 instance used by 0x.js
@@ -130,6 +133,7 @@ export class ZeroEx {
         this.web3Wrapper.setProvider(provider);
         this.exchange.invalidateContractInstance();
         this.tokenRegistry.invalidateContractInstance();
+        this.token.invalidateContractInstances();
     }
     /**
      * Signs an orderHash and returns it's elliptic curve signature
diff --git a/src/contract_wrappers/token_wrapper.ts b/src/contract_wrappers/token_wrapper.ts
new file mode 100644
index 000000000..e93b6b7c2
--- /dev/null
+++ b/src/contract_wrappers/token_wrapper.ts
@@ -0,0 +1,110 @@
+import * as _ from 'lodash';
+import * as BigNumber from 'bignumber.js';
+import {Web3Wrapper} from '../web3_wrapper';
+import {assert} from '../utils/assert';
+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, InternalError} from '../types';
+
+const ALLOWANCE_TO_ZERO_GAS_AMOUNT = 45730;
+
+export class TokenWrapper extends ContractWrapper {
+    private tokenContractsByAddress: {[address: string]: TokenContract};
+    constructor(web3Wrapper: Web3Wrapper) {
+        super(web3Wrapper);
+        this.tokenContractsByAddress = {};
+    }
+    public invalidateContractInstances() {
+        this.tokenContractsByAddress = {};
+    }
+    /**
+     * Returns an owner's ERC20 token balance
+     */
+    public async getBalanceAsync(tokenAddress: string, ownerAddress: string): Promise<BigNumber.BigNumber> {
+        assert.isETHAddressHex('ownerAddress', ownerAddress);
+        assert.isETHAddressHex('tokenAddress', tokenAddress);
+
+        const tokenContract = await this.getTokenContractAsync(tokenAddress);
+        let balance = await tokenContract.balanceOf.call(ownerAddress);
+        // The BigNumber instance returned by Web3 is of a much older version then our own, we therefore
+        // should always re-instantiate the returned BigNumber after retrieval.
+        balance = _.isUndefined(balance) ? new BigNumber(0) : new BigNumber(balance);
+        return balance;
+    }
+    /**
+     * Retrieves the allowance in baseUnits of the ERC20 token set to the 0x proxy contract
+     * by an owner address
+     */
+    public async getProxyAllowanceAsync(tokenAddress: string, ownerAddress: string) {
+        assert.isETHAddressHex('ownerAddress', ownerAddress);
+        assert.isETHAddressHex('tokenAddress', tokenAddress);
+
+        const tokenContract = await this.getTokenContractAsync(tokenAddress);
+        const proxyAddress = await this.getProxyAddressAsync();
+        let allowanceInBaseUnits = await tokenContract.allowance.call(ownerAddress, proxyAddress);
+        allowanceInBaseUnits = _.isUndefined(allowanceInBaseUnits) ?
+                               new BigNumber(0) :
+                               new BigNumber(allowanceInBaseUnits);
+        return allowanceInBaseUnits;
+    }
+    /**
+     * Sets the 0x proxy contract's allowance to a specified number of a tokens' baseUnits on behalf
+     * of an owner address.
+     */
+    public async setProxyAllowanceAsync(tokenAddress: string, ownerAddress: string,
+                                        amountInBaseUnits: BigNumber.BigNumber): Promise<void> {
+        assert.isETHAddressHex('ownerAddress', ownerAddress);
+        assert.isETHAddressHex('tokenAddress', tokenAddress);
+        assert.isBigNumber('amountInBaseUnits', amountInBaseUnits);
+
+        const tokenContract = await this.getTokenContractAsync(tokenAddress);
+        const proxyAddress = await this.getProxyAddressAsync();
+        // Hack: for some reason default estimated gas amount causes `base fee exceeds gas limit` exception
+        // on testrpc. Probably related to https://github.com/ethereumjs/testrpc/issues/294
+        // TODO: Debug issue in testrpc and submit a PR, then remove this hack
+        const networkIdIfExists = await this.web3Wrapper.getNetworkIdIfExistsAsync();
+        const gas = networkIdIfExists === constants.TESTRPC_NETWORK_ID ? ALLOWANCE_TO_ZERO_GAS_AMOUNT : undefined;
+        await tokenContract.approve(proxyAddress, amountInBaseUnits, {
+            from: ownerAddress,
+            gas,
+        });
+    }
+    /**
+     * Transfers `amountInBaseUnits` ERC20 tokens from `fromAddress` to `toAddress`.
+     */
+    public async transferAsync(tokenAddress: string, fromAddress: string, toAddress: string,
+                               amountInBaseUnits: BigNumber.BigNumber): Promise<void> {
+        assert.isETHAddressHex('tokenAddress', tokenAddress);
+        assert.isETHAddressHex('fromAddress', fromAddress);
+        assert.isETHAddressHex('toAddress', toAddress);
+        assert.isBigNumber('amountInBaseUnits', amountInBaseUnits);
+
+        const tokenContract = await this.getTokenContractAsync(tokenAddress);
+        await tokenContract.transfer(toAddress, amountInBaseUnits, {
+            from: fromAddress,
+        });
+    }
+    private async getTokenContractAsync(tokenAddress: string): Promise<TokenContract> {
+        let tokenContract = this.tokenContractsByAddress[tokenAddress];
+        if (!_.isUndefined(tokenContract)) {
+            return tokenContract;
+        }
+        const contractInstance = await this.instantiateContractIfExistsAsync((TokenArtifacts as any), tokenAddress);
+        tokenContract = contractInstance as TokenContract;
+        this.tokenContractsByAddress[tokenAddress] = tokenContract;
+        return tokenContract;
+    }
+    private async getProxyAddressAsync() {
+        const networkIdIfExists = await this.web3Wrapper.getNetworkIdIfExistsAsync();
+        const proxyNetworkConfigsIfExists = _.isUndefined(networkIdIfExists) ?
+                                       undefined :
+                                       (ProxyArtifacts as any).networks[networkIdIfExists];
+        if (_.isUndefined(proxyNetworkConfigsIfExists)) {
+            throw new Error(InternalError.PROXY_ADDRESS_NOT_FOUND);
+        }
+        const proxyAddress = proxyNetworkConfigsIfExists.address;
+        return proxyAddress;
+    }
+}
diff --git a/src/types.ts b/src/types.ts
index dc2a4d848..861df3187 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -17,6 +17,11 @@ export const ZeroExError = strEnum([
 ]);
 export type ZeroExError = keyof typeof ZeroExError;
 
+export const InternalError = strEnum([
+  'PROXY_ADDRESS_NOT_FOUND',
+]);
+export type InternalError = keyof typeof InternalError;
+
 /**
  * Elliptic Curve signature
  */
@@ -45,6 +50,17 @@ export interface ExchangeContract {
     ) => ContractResponse;
 }
 
+export interface TokenContract {
+    balanceOf: {
+        call: (address: string) => Promise<BigNumber.BigNumber>;
+    };
+    allowance: {
+        call: (ownerAddress: string, allowedAddress: string) => Promise<BigNumber.BigNumber>;
+    };
+    transfer: (to: string, amountInBaseUnits: BigNumber.BigNumber, opts: any) => Promise<boolean>;
+    approve: (proxyAddress: string, amountInBaseUnits: BigNumber.BigNumber, opts: any) => void;
+}
+
 export interface TokenRegistryContract {
     getTokenMetaData: {
         call: (address: string) => Promise<TokenMetadata>;
diff --git a/src/utils/constants.ts b/src/utils/constants.ts
index ec2fe744a..5a5ba0e0a 100644
--- a/src/utils/constants.ts
+++ b/src/utils/constants.ts
@@ -1,3 +1,4 @@
 export const constants = {
     NULL_ADDRESS: '0x0000000000000000000000000000000000000000',
+    TESTRPC_NETWORK_ID: 50,
 };