2 files changed, 57 insertions, 1 deletions

diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index 7a80c5800..66e53a7d4 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -26,9 +26,13 @@ export class ExchangeWrapper extends ContractWrapper {
         [ExchangeContractErrs.ERROR_FILL_TRUNCATION]: 'The rounding error was too large when filling this order',
         [ExchangeContractErrs.ERROR_FILL_BALANCE_ALLOWANCE]: 'Maker or taker has insufficient balance or allowance',
     };
+    private exchangeContractIfExists?: ExchangeContract;
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
     }
+    public invalidateContractInstance(): void {
+        delete this.exchangeContractIfExists;
+    }
     public async isValidSignatureAsync(dataHex: string, ecSignature: ECSignature,
                                        signerAddressHex: string): Promise<boolean> {
         assert.isHexString('dataHex', dataHex);
@@ -36,7 +40,7 @@ export class ExchangeWrapper extends ContractWrapper {
         assert.isETHAddressHex('signerAddressHex', signerAddressHex);
 
         const senderAddress = await this.web3Wrapper.getSenderAddressOrThrowAsync();
-        const exchangeInstance = await this.getExchangeInstanceOrThrowAsync();
+        const exchangeInstance = await this.getExchangeContractAsync();
 
         const isValidSignature = await exchangeInstance.isValidSignature.call(
             signerAddressHex,
@@ -102,4 +106,12 @@ export class ExchangeWrapper extends ContractWrapper {
             throw new Error(humanReadableErrMessage);
         }
     }
+    private async getExchangeContractAsync(): Promise<ExchangeContract> {
+        if (!_.isUndefined(this.exchangeContractIfExists)) {
+            return this.exchangeContractIfExists;
+        }
+        const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
+        this.exchangeContractIfExists = contractInstance as ExchangeContract;
+        return this.exchangeContractIfExists;
+    }
 }
diff --git a/src/contract_wrappers/token_registry_wrapper.ts b/src/contract_wrappers/token_registry_wrapper.ts
new file mode 100644
index 000000000..86bea1c5d
--- /dev/null
+++ b/src/contract_wrappers/token_registry_wrapper.ts
@@ -0,0 +1,44 @@
+import * as _ from 'lodash';
+import {Web3Wrapper} from '../web3_wrapper';
+import {Token, TokenRegistryContract, TokenMetadata} from '../types';
+import {assert} from '../utils/assert';
+import {ContractWrapper} from './contract_wrapper';
+import * as TokenRegistryArtifacts from '../artifacts/TokenRegistry.json';
+
+export class TokenRegistryWrapper extends ContractWrapper {
+    private tokenRegistryContractIfExists?: TokenRegistryContract;
+    constructor(web3Wrapper: Web3Wrapper) {
+        super(web3Wrapper);
+    }
+    public invalidateContractInstance(): void {
+        delete this.tokenRegistryContractIfExists;
+    }
+    public async getTokensAsync(): Promise<Token[]> {
+        const tokenRegistryContract = await this.getTokenRegistryContractAsync();
+
+        const addresses = await tokenRegistryContract.getTokenAddresses.call();
+        const tokenMetadataPromises: Array<Promise<TokenMetadata>> = _.map(
+            addresses,
+            (address: string) => (tokenRegistryContract.getTokenMetaData.call(address)),
+        );
+        const tokensMetadata = await Promise.all(tokenMetadataPromises);
+        const tokens = _.map(tokensMetadata, metadata => {
+            return {
+                address: metadata[0],
+                name: metadata[1],
+                symbol: metadata[2],
+                url: metadata[3],
+                decimals: metadata[4].toNumber(),
+            };
+        });
+        return tokens;
+    }
+    private async getTokenRegistryContractAsync(): Promise<TokenRegistryContract> {
+        if (!_.isUndefined(this.tokenRegistryContractIfExists)) {
+            return this.tokenRegistryContractIfExists;
+        }
+        const contractInstance = await this.instantiateContractIfExistsAsync((TokenRegistryArtifacts as any));
+        this.tokenRegistryContractIfExists = contractInstance as TokenRegistryContract;
+        return this.tokenRegistryContractIfExists;
+    }
+}