Minimize unnecessary type assertions

1 files changed, 52 insertions, 80 deletions

diff --git a/packages/contract-wrappers/src/fetchers/asset_balance_and_proxy_allowance_fetcher.ts b/packages/contract-wrappers/src/fetchers/asset_balance_and_proxy_allowance_fetcher.ts
index 376004f52..1ff130a48 100644
--- a/packages/contract-wrappers/src/fetchers/asset_balance_and_proxy_allowance_fetcher.ts
+++ b/packages/contract-wrappers/src/fetchers/asset_balance_and_proxy_allowance_fetcher.ts
@@ -1,6 +1,4 @@
-// tslint:disable:no-unnecessary-type-assertion
 import { AbstractBalanceAndProxyAllowanceFetcher, assetDataUtils } from '@0x/order-utils';
-import { AssetProxyId, ERC20AssetData, ERC721AssetData, MultiAssetData } from '@0x/types';
 import { BigNumber } from '@0x/utils';
 import { BlockParamLiteral } from 'ethereum-types';
 import * as _ from 'lodash';
@@ -20,99 +18,73 @@ export class AssetBalanceAndProxyAllowanceFetcher implements AbstractBalanceAndP
     public async getBalanceAsync(assetData: string, userAddress: string): Promise<BigNumber> {
         const decodedAssetData = assetDataUtils.decodeAssetDataOrThrow(assetData);
         let balance: BigNumber | undefined;
-        switch (decodedAssetData.assetProxyId) {
-            case AssetProxyId.ERC20:
-                const decodedERC20AssetData = decodedAssetData as ERC20AssetData;
-                balance = await this._erc20Token.getBalanceAsync(decodedERC20AssetData.tokenAddress, userAddress, {
+        if (assetDataUtils.isERC20AssetData(decodedAssetData)) {
+            balance = await this._erc20Token.getBalanceAsync(decodedAssetData.tokenAddress, userAddress, {
+                defaultBlock: this._stateLayer,
+            });
+        } else if (assetDataUtils.isERC721AssetData(decodedAssetData)) {
+            const tokenOwner = await this._erc721Token.getOwnerOfAsync(
+                decodedAssetData.tokenAddress,
+                decodedAssetData.tokenId,
+                {
                     defaultBlock: this._stateLayer,
-                });
-                break;
-            case AssetProxyId.ERC721:
-                const decodedERC721AssetData = decodedAssetData as ERC721AssetData;
-                const tokenOwner = await this._erc721Token.getOwnerOfAsync(
-                    decodedERC721AssetData.tokenAddress,
-                    decodedERC721AssetData.tokenId,
-                    {
-                        defaultBlock: this._stateLayer,
-                    },
-                );
-                balance = tokenOwner === userAddress ? new BigNumber(1) : new BigNumber(0);
-                break;
-            case AssetProxyId.MultiAsset:
-                // The `balance` for MultiAssetData is the total units of the entire `assetData` that are held by the `userAddress`.
-                for (const [
-                    index,
+                },
+            );
+            balance = tokenOwner === userAddress ? new BigNumber(1) : new BigNumber(0);
+        } else if (assetDataUtils.isMultiAssetData(decodedAssetData)) {
+            // The `balance` for MultiAssetData is the total units of the entire `assetData` that are held by the `userAddress`.
+            for (const [index, nestedAssetDataElement] of decodedAssetData.nestedAssetData.entries()) {
+                const nestedAmountElement = decodedAssetData.amounts[index];
+                const nestedAssetBalance = (await this.getBalanceAsync(
                     nestedAssetDataElement,
-                ] of (decodedAssetData as MultiAssetData).nestedAssetData.entries()) {
-                    const nestedAmountElement = (decodedAssetData as MultiAssetData).amounts[index];
-                    const nestedAssetBalance = (await this.getBalanceAsync(
-                        nestedAssetDataElement,
-                        userAddress,
-                    )).dividedToIntegerBy(nestedAmountElement);
-                    if (_.isUndefined(balance) || nestedAssetBalance.lessThan(balance)) {
-                        balance = nestedAssetBalance;
-                    }
+                    userAddress,
+                )).dividedToIntegerBy(nestedAmountElement);
+                if (_.isUndefined(balance) || nestedAssetBalance.lessThan(balance)) {
+                    balance = nestedAssetBalance;
                 }
-                break;
-            default:
-                throw new Error(`Proxy with id ${decodedAssetData.assetProxyId} not supported`);
+            }
         }
         return balance as BigNumber;
     }
     public async getProxyAllowanceAsync(assetData: string, userAddress: string): Promise<BigNumber> {
         const decodedAssetData = assetDataUtils.decodeAssetDataOrThrow(assetData);
         let proxyAllowance: BigNumber | undefined;
-        switch (decodedAssetData.assetProxyId) {
-            case AssetProxyId.ERC20:
-                const decodedERC20AssetData = decodedAssetData as ERC20AssetData;
-                proxyAllowance = await this._erc20Token.getProxyAllowanceAsync(
-                    decodedERC20AssetData.tokenAddress,
-                    userAddress,
-                    {
-                        defaultBlock: this._stateLayer,
-                    },
-                );
-                break;
-            case AssetProxyId.ERC721:
-                const decodedERC721AssetData = decodedAssetData as ERC721AssetData;
-                const isApprovedForAll = await this._erc721Token.isProxyApprovedForAllAsync(
-                    decodedERC721AssetData.tokenAddress,
-                    userAddress,
+        if (assetDataUtils.isERC20AssetData(decodedAssetData)) {
+            proxyAllowance = await this._erc20Token.getProxyAllowanceAsync(decodedAssetData.tokenAddress, userAddress, {
+                defaultBlock: this._stateLayer,
+            });
+        } else if (assetDataUtils.isERC721AssetData(decodedAssetData)) {
+            const isApprovedForAll = await this._erc721Token.isProxyApprovedForAllAsync(
+                decodedAssetData.tokenAddress,
+                userAddress,
+                {
+                    defaultBlock: this._stateLayer,
+                },
+            );
+            if (isApprovedForAll) {
+                return new BigNumber(this._erc20Token.UNLIMITED_ALLOWANCE_IN_BASE_UNITS);
+            } else {
+                const isApproved = await this._erc721Token.isProxyApprovedAsync(
+                    decodedAssetData.tokenAddress,
+                    decodedAssetData.tokenId,
                     {
                         defaultBlock: this._stateLayer,
                     },
                 );
-                if (isApprovedForAll) {
-                    return new BigNumber(this._erc20Token.UNLIMITED_ALLOWANCE_IN_BASE_UNITS);
-                } else {
-                    const isApproved = await this._erc721Token.isProxyApprovedAsync(
-                        decodedERC721AssetData.tokenAddress,
-                        decodedERC721AssetData.tokenId,
-                        {
-                            defaultBlock: this._stateLayer,
-                        },
-                    );
-                    proxyAllowance = isApproved ? new BigNumber(1) : new BigNumber(0);
-                }
-                break;
-            case AssetProxyId.MultiAsset:
-                // The `proxyAllowance` for MultiAssetData is the total units of the entire `assetData` that the proxies have been approved to spend by the `userAddress`.
-                for (const [
-                    index,
+                proxyAllowance = isApproved ? new BigNumber(1) : new BigNumber(0);
+            }
+        } else if (assetDataUtils.isMultiAssetData(decodedAssetData)) {
+            // The `proxyAllowance` for MultiAssetData is the total units of the entire `assetData` that the proxies have been approved to spend by the `userAddress`.
+            for (const [index, nestedAssetDataElement] of decodedAssetData.nestedAssetData.entries()) {
+                const nestedAmountElement = decodedAssetData.amounts[index];
+                const nestedAssetAllowance = (await this.getProxyAllowanceAsync(
                     nestedAssetDataElement,
-                ] of (decodedAssetData as MultiAssetData).nestedAssetData.entries()) {
-                    const nestedAmountElement = (decodedAssetData as MultiAssetData).amounts[index];
-                    const nestedAssetAllowance = (await this.getProxyAllowanceAsync(
-                        nestedAssetDataElement,
-                        userAddress,
-                    )).dividedToIntegerBy(nestedAmountElement);
-                    if (_.isUndefined(proxyAllowance) || nestedAssetAllowance.lessThan(proxyAllowance)) {
-                        proxyAllowance = nestedAssetAllowance;
-                    }
+                    userAddress,
+                )).dividedToIntegerBy(nestedAmountElement);
+                if (_.isUndefined(proxyAllowance) || nestedAssetAllowance.lessThan(proxyAllowance)) {
+                    proxyAllowance = nestedAssetAllowance;
                 }
-                break;
-            default:
-                throw new Error(`Proxy with id ${decodedAssetData.assetProxyId} not supported`);
+            }
         }
         return proxyAllowance as BigNumber;
     }