From b5e496ea0f04206b74b37d71d6ba3e6975206efc Mon Sep 17 00:00:00 2001
From: Fabio Berger <me@fabioberger.com>
Date: Tue, 30 May 2017 15:27:51 +0200
Subject: Implement zeroEx.token.getProxyAllowanceAsync

---
 src/contract_wrappers/token_wrapper.ts | 27 ++++++++++++++++++++++++++-
 src/types.ts                           |  8 ++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/contract_wrappers/token_wrapper.ts b/src/contract_wrappers/token_wrapper.ts
index fe1d0c89f..0282d8266 100644
--- a/src/contract_wrappers/token_wrapper.ts
+++ b/src/contract_wrappers/token_wrapper.ts
@@ -4,7 +4,8 @@ import {Web3Wrapper} from '../web3_wrapper';
 import {assert} from '../utils/assert';
 import {ContractWrapper} from './contract_wrapper';
 import * as TokenArtifacts from '../artifacts/Token.json';
-import {TokenContract} from '../types';
+import * as ProxyArtifacts from '../artifacts/Proxy.json';
+import {TokenContract, InternalError} from '../types';
 
 export class TokenWrapper extends ContractWrapper {
     private tokenContractsByAddress: {[address: string]: TokenContract};
@@ -29,6 +30,19 @@ export class TokenWrapper extends ContractWrapper {
         balance = _.isUndefined(balance) ? new BigNumber(0) : new BigNumber(balance);
         return balance;
     }
+    /**
+     * Retrieves the allowance of an 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 allowance = await tokenContract.allowance.call(ownerAddress, proxyAddress);
+        allowance = _.isUndefined(allowance) ? new BigNumber(0) : new BigNumber(allowance);
+        return allowance;
+    }
     private async getTokenContractAsync(tokenAddress: string): Promise<TokenContract> {
         let tokenContract = this.tokenContractsByAddress[tokenAddress];
         if (!_.isUndefined(tokenContract)) {
@@ -39,4 +53,15 @@ export class TokenWrapper extends ContractWrapper {
         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 e1c68e8ae..c2a048e8a 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
  */
@@ -34,6 +39,9 @@ export interface TokenContract {
     balanceOf: {
         call: (address: string) => Promise<BigNumber.BigNumber>;
     };
+    allowance: {
+        call: (ownerAddress: string, allowedAddress: string) => Promise<BigNumber.BigNumber>;
+    };
 }
 
 export interface TokenRegistryContract {
-- 
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