Minimize unnecessary type assertions

5 files changed, 112 insertions, 98 deletions

diff --git a/packages/order-utils/src/asset_data_utils.ts b/packages/order-utils/src/asset_data_utils.ts
index c2929d426..0526c3d00 100644
--- a/packages/order-utils/src/asset_data_utils.ts
+++ b/packages/order-utils/src/asset_data_utils.ts
@@ -7,7 +7,6 @@ import {
     SingleAssetData,
 } from '@0x/types';
 import { AbiEncoder, BigNumber } from '@0x/utils';
-import { MethodAbi } from 'ethereum-types';
 import * as _ from 'lodash';
 
 import { constants } from './constants';
@@ -23,7 +22,7 @@ export const assetDataUtils = {
      * @return The hex encoded assetData string
      */
     encodeERC20AssetData(tokenAddress: string): string {
-        const abiEncoder = new AbiEncoder.Method(constants.ERC20_METHOD_ABI as MethodAbi);
+        const abiEncoder = new AbiEncoder.Method(constants.ERC20_METHOD_ABI);
         const args = [tokenAddress];
         const assetData = abiEncoder.encode(args, encodingRules);
         return assetData;
@@ -36,7 +35,7 @@ export const assetDataUtils = {
     decodeERC20AssetData(assetData: string): ERC20AssetData {
         assetDataUtils.assertIsERC20AssetData(assetData);
         const assetProxyId = assetDataUtils.decodeAssetProxyId(assetData);
-        const abiEncoder = new AbiEncoder.Method(constants.ERC20_METHOD_ABI as MethodAbi);
+        const abiEncoder = new AbiEncoder.Method(constants.ERC20_METHOD_ABI);
         const decodedAssetData = abiEncoder.decode(assetData, decodingRules);
         return {
             assetProxyId,
@@ -52,7 +51,7 @@ export const assetDataUtils = {
      * @return The hex encoded assetData string
      */
     encodeERC721AssetData(tokenAddress: string, tokenId: BigNumber): string {
-        const abiEncoder = new AbiEncoder.Method(constants.ERC721_METHOD_ABI as MethodAbi);
+        const abiEncoder = new AbiEncoder.Method(constants.ERC721_METHOD_ABI);
         const args = [tokenAddress, tokenId];
         const assetData = abiEncoder.encode(args, encodingRules);
         return assetData;
@@ -65,7 +64,7 @@ export const assetDataUtils = {
     decodeERC721AssetData(assetData: string): ERC721AssetData {
         assetDataUtils.assertIsERC721AssetData(assetData);
         const assetProxyId = assetDataUtils.decodeAssetProxyId(assetData);
-        const abiEncoder = new AbiEncoder.Method(constants.ERC721_METHOD_ABI as MethodAbi);
+        const abiEncoder = new AbiEncoder.Method(constants.ERC721_METHOD_ABI);
         const decodedAssetData = abiEncoder.decode(assetData, decodingRules);
         return {
             assetProxyId,
@@ -90,7 +89,7 @@ export const assetDataUtils = {
             );
         }
         _.forEach(nestedAssetData, assetDataElement => assetDataUtils.validateAssetDataOrThrow(assetDataElement));
-        const abiEncoder = new AbiEncoder.Method(constants.MULTI_ASSET_METHOD_ABI as MethodAbi);
+        const abiEncoder = new AbiEncoder.Method(constants.MULTI_ASSET_METHOD_ABI);
         const args = [amounts, nestedAssetData];
         const assetData = abiEncoder.encode(args, encodingRules);
         return assetData;
@@ -103,7 +102,7 @@ export const assetDataUtils = {
     decodeMultiAssetData(assetData: string): MultiAssetData {
         assetDataUtils.assertIsMultiAssetData(assetData);
         const assetProxyId = assetDataUtils.decodeAssetProxyId(assetData);
-        const abiEncoder = new AbiEncoder.Method(constants.MULTI_ASSET_METHOD_ABI as MethodAbi);
+        const abiEncoder = new AbiEncoder.Method(constants.MULTI_ASSET_METHOD_ABI);
         const decodedAssetData = abiEncoder.decode(assetData, decodingRules);
         // TODO(abandeali1): fix return types for `AbiEncoder.Method.decode` so that we can remove type assertion
         const amounts = (decodedAssetData as any).amounts;
@@ -138,7 +137,7 @@ export const assetDataUtils = {
                         nestedAssetDataElement,
                     );
                     amounts.push(
-                        _.map(recursivelyDecodedAssetData.amounts as BigNumber[], amountElement =>
+                        _.map(recursivelyDecodedAssetData.amounts, amountElement =>
                             amountElement.times(decodedAssetData.amounts[index]),
                         ),
                     );
@@ -182,6 +181,27 @@ export const assetDataUtils = {
         return assetProxyId;
     },
     /**
+     * Checks if the decoded asset data is valid ERC20 data
+     * @param decodedAssetData The decoded asset data to check
+     */
+    isERC20AssetData(decodedAssetData: SingleAssetData | MultiAssetData): decodedAssetData is ERC20AssetData {
+        return decodedAssetData.assetProxyId === AssetProxyId.ERC20;
+    },
+    /**
+     * Checks if the decoded asset data is valid ERC721 data
+     * @param decodedAssetData The decoded asset data to check
+     */
+    isERC721AssetData(decodedAssetData: SingleAssetData | MultiAssetData): decodedAssetData is ERC721AssetData {
+        return decodedAssetData.assetProxyId === AssetProxyId.ERC721;
+    },
+    /**
+     * Checks if the decoded asset data is valid MultiAsset data
+     * @param decodedAssetData The decoded asset data to check
+     */
+    isMultiAssetData(decodedAssetData: SingleAssetData | MultiAssetData): decodedAssetData is MultiAssetData {
+        return decodedAssetData.assetProxyId === AssetProxyId.MultiAsset;
+    },
+    /**
      * Throws if the length or assetProxyId are invalid for the ERC20Proxy.
      * @param assetData Hex encoded assetData string
      */
diff --git a/packages/order-utils/src/constants.ts b/packages/order-utils/src/constants.ts
index 1248a5576..a9a687719 100644
--- a/packages/order-utils/src/constants.ts
+++ b/packages/order-utils/src/constants.ts
@@ -1,4 +1,58 @@
 import { BigNumber } from '@0x/utils';
+import { MethodAbi } from 'ethereum-types';
+
+const ERC20_METHOD_ABI: MethodAbi = {
+    constant: false,
+    inputs: [
+        {
+            name: 'tokenContract',
+            type: 'address',
+        },
+    ],
+    name: 'ERC20Token',
+    outputs: [],
+    payable: false,
+    stateMutability: 'nonpayable',
+    type: 'function',
+};
+
+const ERC721_METHOD_ABI: MethodAbi = {
+    constant: false,
+    inputs: [
+        {
+            name: 'tokenContract',
+            type: 'address',
+        },
+        {
+            name: 'tokenId',
+            type: 'uint256',
+        },
+    ],
+    name: 'ERC721Token',
+    outputs: [],
+    payable: false,
+    stateMutability: 'nonpayable',
+    type: 'function',
+};
+
+const MULTI_ASSET_METHOD_ABI: MethodAbi = {
+    constant: false,
+    inputs: [
+        {
+            name: 'amounts',
+            type: 'uint256[]',
+        },
+        {
+            name: 'nestedAssetData',
+            type: 'bytes[]',
+        },
+    ],
+    name: 'MultiAsset',
+    outputs: [],
+    payable: false,
+    stateMutability: 'nonpayable',
+    type: 'function',
+};
 
 export const constants = {
     NULL_ADDRESS: '0x0000000000000000000000000000000000000000',
@@ -49,54 +103,7 @@ export const constants = {
             { name: 'data', type: 'bytes' },
         ],
     },
-    ERC20_METHOD_ABI: {
-        constant: false,
-        inputs: [
-            {
-                name: 'tokenContract',
-                type: 'address',
-            },
-        ],
-        name: 'ERC20Token',
-        outputs: [],
-        payable: false,
-        stateMutability: 'nonpayable',
-        type: 'function',
-    },
-    ERC721_METHOD_ABI: {
-        constant: false,
-        inputs: [
-            {
-                name: 'tokenContract',
-                type: 'address',
-            },
-            {
-                name: 'tokenId',
-                type: 'uint256',
-            },
-        ],
-        name: 'ERC721Token',
-        outputs: [],
-        payable: false,
-        stateMutability: 'nonpayable',
-        type: 'function',
-    },
-    MULTI_ASSET_METHOD_ABI: {
-        constant: false,
-        inputs: [
-            {
-                name: 'amounts',
-                type: 'uint256[]',
-            },
-            {
-                name: 'nestedAssetData',
-                type: 'bytes[]',
-            },
-        ],
-        name: 'MultiAsset',
-        outputs: [],
-        payable: false,
-        stateMutability: 'nonpayable',
-        type: 'function',
-    },
+    ERC20_METHOD_ABI,
+    ERC721_METHOD_ABI,
+    MULTI_ASSET_METHOD_ABI,
 };
diff --git a/packages/order-utils/src/exchange_transfer_simulator.ts b/packages/order-utils/src/exchange_transfer_simulator.ts
index 0a948fd1f..06621fd9e 100644
--- a/packages/order-utils/src/exchange_transfer_simulator.ts
+++ b/packages/order-utils/src/exchange_transfer_simulator.ts
@@ -108,7 +108,7 @@ export class ExchangeTransferSimulator {
                     const amountsElement = decodedAssetData.amounts[index];
                     const totalAmount = amountInBaseUnits.times(amountsElement);
                     await this.transferFromAsync(
-                        nestedAssetDataElement as string,
+                        nestedAssetDataElement,
                         from,
                         to,
                         totalAmount,
diff --git a/packages/order-utils/src/order_state_utils.ts b/packages/order-utils/src/order_state_utils.ts
index 9e3e228ba..389419587 100644
--- a/packages/order-utils/src/order_state_utils.ts
+++ b/packages/order-utils/src/order_state_utils.ts
@@ -1,14 +1,11 @@
 import {
-    AssetProxyId,
     ExchangeContractErrs,
-    MultiAssetData,
     ObjectMap,
     OrderRelevantState,
     OrderState,
     OrderStateInvalid,
     OrderStateValid,
     SignedOrder,
-    SingleAssetData,
 } from '@0x/types';
 import { BigNumber } from '@0x/utils';
 import * as _ from 'lodash';
@@ -310,22 +307,16 @@ export class OrderStateUtils {
     ): Promise<ObjectMap<BigNumber>> {
         const decodedAssetData = assetDataUtils.decodeAssetDataOrThrow(assetData);
         let balances: ObjectMap<BigNumber> = { ...initialBalances };
-        switch (decodedAssetData.assetProxyId) {
-            case AssetProxyId.ERC20:
-            case AssetProxyId.ERC721:
-                const balance = await this._balanceAndProxyAllowanceFetcher.getBalanceAsync(assetData, traderAddress);
-                const tokenAddress = (decodedAssetData as SingleAssetData).tokenAddress;
-                balances[tokenAddress] = _.isUndefined(initialBalances[tokenAddress])
-                    ? balance
-                    : balances[tokenAddress].add(balance);
-                break;
-            case AssetProxyId.MultiAsset:
-                for (const assetDataElement of (decodedAssetData as MultiAssetData).nestedAssetData) {
-                    balances = await this._getAssetBalancesAsync(assetDataElement, traderAddress, balances);
-                }
-                break;
-            default:
-                throw new Error(`Proxy with id ${decodedAssetData.assetProxyId} not supported`);
+        if (assetDataUtils.isERC20AssetData(decodedAssetData) || assetDataUtils.isERC721AssetData(decodedAssetData)) {
+            const balance = await this._balanceAndProxyAllowanceFetcher.getBalanceAsync(assetData, traderAddress);
+            const tokenAddress = decodedAssetData.tokenAddress;
+            balances[tokenAddress] = _.isUndefined(initialBalances[tokenAddress])
+                ? balance
+                : balances[tokenAddress].add(balance);
+        } else if (assetDataUtils.isMultiAssetData(decodedAssetData)) {
+            for (const assetDataElement of decodedAssetData.nestedAssetData) {
+                balances = await this._getAssetBalancesAsync(assetDataElement, traderAddress, balances);
+            }
         }
         return balances;
     }
@@ -336,25 +327,19 @@ export class OrderStateUtils {
     ): Promise<ObjectMap<BigNumber>> {
         const decodedAssetData = assetDataUtils.decodeAssetDataOrThrow(assetData);
         let allowances: ObjectMap<BigNumber> = { ...initialAllowances };
-        switch (decodedAssetData.assetProxyId) {
-            case AssetProxyId.ERC20:
-            case AssetProxyId.ERC721:
-                const allowance = await this._balanceAndProxyAllowanceFetcher.getProxyAllowanceAsync(
-                    assetData,
-                    traderAddress,
-                );
-                const tokenAddress = (decodedAssetData as SingleAssetData).tokenAddress;
-                allowances[tokenAddress] = _.isUndefined(initialAllowances[tokenAddress])
-                    ? allowance
-                    : allowances[tokenAddress].add(allowance);
-                break;
-            case AssetProxyId.MultiAsset:
-                for (const assetDataElement of (decodedAssetData as MultiAssetData).nestedAssetData) {
-                    allowances = await this._getAssetBalancesAsync(assetDataElement, traderAddress, allowances);
-                }
-                break;
-            default:
-                throw new Error(`Proxy with id ${decodedAssetData.assetProxyId} not supported`);
+        if (assetDataUtils.isERC20AssetData(decodedAssetData) || assetDataUtils.isERC721AssetData(decodedAssetData)) {
+            const allowance = await this._balanceAndProxyAllowanceFetcher.getProxyAllowanceAsync(
+                assetData,
+                traderAddress,
+            );
+            const tokenAddress = decodedAssetData.tokenAddress;
+            allowances[tokenAddress] = _.isUndefined(initialAllowances[tokenAddress])
+                ? allowance
+                : allowances[tokenAddress].add(allowance);
+        } else if (assetDataUtils.isMultiAssetData(decodedAssetData)) {
+            for (const assetDataElement of decodedAssetData.nestedAssetData) {
+                allowances = await this._getAssetBalancesAsync(assetDataElement, traderAddress, allowances);
+            }
         }
         return allowances;
     }
diff --git a/packages/order-utils/test/asset_data_utils_test.ts b/packages/order-utils/test/asset_data_utils_test.ts
index ebc5bdeac..c498c5a00 100644
--- a/packages/order-utils/test/asset_data_utils_test.ts
+++ b/packages/order-utils/test/asset_data_utils_test.ts
@@ -27,7 +27,6 @@ const KNOWN_MULTI_ASSET_ENCODING = {
         '0x94cfcdd7000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000024f47261b00000000000000000000000001dc4c1cefef38a777b15aa20260a54e584b16c48000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044025717920000000000000000000000001dc4c1cefef38a777b15aa20260a54e584b16c48000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000',
 };
 
-// tslint:disable:no-unnecessary-type-assertion
 describe('assetDataUtils', () => {
     it('should encode ERC20', () => {
         const assetData = assetDataUtils.encodeERC20AssetData(KNOWN_ERC20_ENCODING.address);
@@ -69,6 +68,7 @@ describe('assetDataUtils', () => {
         expect(decodedAssetData.assetProxyId).to.equal(AssetProxyId.MultiAsset);
         expect(decodedAssetData.amounts).to.deep.equal(KNOWN_MULTI_ASSET_ENCODING.amounts);
         const decodedErc20AssetData = decodedAssetData.nestedAssetData[0];
+        // tslint:disable-next-line:no-unnecessary-type-assertion
         const decodedErc721AssetData = decodedAssetData.nestedAssetData[1] as ERC721AssetData;
         expect(decodedErc20AssetData.tokenAddress).to.equal(KNOWN_ERC20_ENCODING.address);
         expect(decodedErc20AssetData.assetProxyId).to.equal(AssetProxyId.ERC20);
@@ -91,8 +91,10 @@ describe('assetDataUtils', () => {
         const expectedLength = 4;
         expect(decodedAssetData.nestedAssetData.length).to.be.equal(expectedLength);
         const decodedErc20AssetData1 = decodedAssetData.nestedAssetData[0];
+        // tslint:disable-next-line:no-unnecessary-type-assertion
         const decodedErc721AssetData1 = decodedAssetData.nestedAssetData[1] as ERC721AssetData;
         const decodedErc20AssetData2 = decodedAssetData.nestedAssetData[2];
+        // tslint:disable-next-line:no-unnecessary-type-assertion
         const decodedErc721AssetData2 = decodedAssetData.nestedAssetData[3] as ERC721AssetData;
         expect(decodedErc20AssetData1.tokenAddress).to.equal(KNOWN_ERC20_ENCODING.address);
         expect(decodedErc20AssetData1.assetProxyId).to.equal(AssetProxyId.ERC20);