Merge branch 'v2-prototype' into feature/combinatorial-testing

* v2-prototype: (21 commits)
  Don't use variables for revert reasons
  Add comments to dispatchTransferFrom
  Document IAssetData
  Compute bytes4 proxyid constants
  Return inplace bytes in LibBytes.readBytesWithLength
  Add Greg's documentation to MixinErc721Transfer
  Add Greg's documentation to MixinErc20Transfer
  Gas golf the transfer success logic
  Optimize like in PR #767
  Run prettier and fix linting errors
  Fix tests
  Update tests
  Fix AssetProxyUtils
  Update tests
  Fix ERC721Proxy TokenId
  Update AssetProxyUtils
  Add IAssetData
  WIP
  ABI encoded asset data
  Remove proxyId argument from dispatchTransferFrom
  ...

# Conflicts:
#	packages/contracts/test/asset_proxy/proxies.ts

2 files changed, 67 insertions, 93 deletions

diff --git a/packages/order-utils/src/asset_proxy_utils.ts b/packages/order-utils/src/asset_proxy_utils.ts
index 915ee5032..8140ad89d 100644
--- a/packages/order-utils/src/asset_proxy_utils.ts
+++ b/packages/order-utils/src/asset_proxy_utils.ts
@@ -1,32 +1,43 @@
 import { AssetProxyId, ERC20AssetData, ERC721AssetData } from '@0xproject/types';
-import { BigNumber, NULL_BYTES } from '@0xproject/utils';
+import { BigNumber } from '@0xproject/utils';
 import BN = require('bn.js');
 import ethUtil = require('ethereumjs-util');
-import * as _ from 'lodash';
 
-const ERC20_ASSET_DATA_BYTE_LENGTH = 21;
-const ERC721_ASSET_DATA_MINIMUM_BYTE_LENGTH = 53;
-const ASSET_DATA_ADDRESS_OFFSET = 0;
-const ERC721_ASSET_DATA_TOKEN_ID_OFFSET = 20;
-const ERC721_ASSET_DATA_RECEIVER_DATA_LENGTH_OFFSET = 52;
-const ERC721_ASSET_DATA_RECEIVER_DATA_OFFSET = 84;
+import { constants } from './constants';
+
+// TODO: Push upstream to DefinitelyTyped
+interface EthAbi {
+    simpleEncode(signature: string, ...args: any[]): Buffer;
+    rawDecode(signature: string[], data: Buffer): any[];
+}
+// tslint:disable:no-var-requires
+const ethAbi = require('ethereumjs-abi') as EthAbi;
 
 export const assetProxyUtils = {
     encodeAssetProxyId(assetProxyId: AssetProxyId): Buffer {
         return ethUtil.toBuffer(assetProxyId);
     },
     decodeAssetProxyId(encodedAssetProxyId: Buffer): AssetProxyId {
-        return ethUtil.bufferToInt(encodedAssetProxyId);
+        const hexString = ethUtil.bufferToHex(encodedAssetProxyId);
+        if (hexString === AssetProxyId.ERC20) {
+            return AssetProxyId.ERC20;
+        }
+        if (hexString === AssetProxyId.ERC721) {
+            return AssetProxyId.ERC721;
+        }
+        throw new Error(`Invalid ProxyId: ${hexString}`);
     },
     encodeAddress(address: string): Buffer {
         if (!ethUtil.isValidAddress(address)) {
             throw new Error(`Invalid Address: ${address}`);
         }
         const encodedAddress = ethUtil.toBuffer(address);
-        return encodedAddress;
+        const padded = ethUtil.setLengthLeft(encodedAddress, constants.WORD_LENGTH);
+        return padded;
     },
     decodeAddress(encodedAddress: Buffer): string {
-        const address = ethUtil.bufferToHex(encodedAddress);
+        const unpadded = ethUtil.setLengthLeft(encodedAddress, constants.ADDRESS_LENGTH);
+        const address = ethUtil.bufferToHex(unpadded);
         if (!ethUtil.isValidAddress(address)) {
             throw new Error(`Invalid Address: ${address}`);
         }
@@ -37,33 +48,27 @@ export const assetProxyUtils = {
         const formattedValue = new BN(value.toString(base));
         const encodedValue = ethUtil.toBuffer(formattedValue);
         // tslint:disable-next-line:custom-no-magic-numbers
-        const paddedValue = ethUtil.setLengthLeft(encodedValue, 32);
+        const paddedValue = ethUtil.setLengthLeft(encodedValue, constants.WORD_LENGTH);
         return paddedValue;
     },
     decodeUint256(encodedValue: Buffer): BigNumber {
         const formattedValue = ethUtil.bufferToHex(encodedValue);
-        const value = new BigNumber(formattedValue, 16);
+        const value = new BigNumber(formattedValue, constants.BASE_16);
         return value;
     },
     encodeERC20AssetData(tokenAddress: string): string {
-        const encodedAssetProxyId = assetProxyUtils.encodeAssetProxyId(AssetProxyId.ERC20);
-        const encodedAddress = assetProxyUtils.encodeAddress(tokenAddress);
-        const encodedAssetData = Buffer.concat([encodedAddress, encodedAssetProxyId]);
-        const encodedAssetDataHex = ethUtil.bufferToHex(encodedAssetData);
-        return encodedAssetDataHex;
+        return ethUtil.bufferToHex(ethAbi.simpleEncode('ERC20Token(address)', tokenAddress));
     },
-    decodeERC20AssetData(proxyData: string): ERC20AssetData {
-        const encodedAssetData = ethUtil.toBuffer(proxyData);
-        if (encodedAssetData.byteLength !== ERC20_ASSET_DATA_BYTE_LENGTH) {
+    decodeERC20AssetData(assetData: string): ERC20AssetData {
+        const data = ethUtil.toBuffer(assetData);
+        if (data.byteLength < constants.ERC20_ASSET_DATA_BYTE_LENGTH) {
             throw new Error(
-                `Could not decode ERC20 Proxy Data. Expected length of encoded data to be 21. Got ${
-                    encodedAssetData.byteLength
-                }`,
+                `Could not decode ERC20 Proxy Data. Expected length of encoded data to be at least ${
+                    constants.ERC20_ASSET_DATA_BYTE_LENGTH
+                }. Got ${data.byteLength}`,
             );
         }
-        const assetProxyIdOffset = encodedAssetData.byteLength - 1;
-        const encodedAssetProxyId = encodedAssetData.slice(assetProxyIdOffset);
-        const assetProxyId = assetProxyUtils.decodeAssetProxyId(encodedAssetProxyId);
+        const assetProxyId = ethUtil.bufferToHex(data.slice(0, constants.SELECTOR_LENGTH));
         if (assetProxyId !== AssetProxyId.ERC20) {
             throw new Error(
                 `Could not decode ERC20 Proxy Data. Expected Asset Proxy Id to be ERC20 (${
@@ -71,98 +76,61 @@ export const assetProxyUtils = {
                 }), but got ${assetProxyId}`,
             );
         }
-        const encodedTokenAddress = encodedAssetData.slice(ASSET_DATA_ADDRESS_OFFSET, assetProxyIdOffset);
-        const tokenAddress = assetProxyUtils.decodeAddress(encodedTokenAddress);
-        const erc20AssetData = {
+        const [tokenAddress] = ethAbi.rawDecode(['address'], data.slice(constants.SELECTOR_LENGTH));
+        return {
             assetProxyId,
-            tokenAddress,
+            tokenAddress: ethUtil.addHexPrefix(tokenAddress),
         };
-        return erc20AssetData;
     },
     encodeERC721AssetData(tokenAddress: string, tokenId: BigNumber, receiverData?: string): string {
-        const encodedAssetProxyId = assetProxyUtils.encodeAssetProxyId(AssetProxyId.ERC721);
-        const encodedAddress = assetProxyUtils.encodeAddress(tokenAddress);
-        const encodedTokenId = assetProxyUtils.encodeUint256(tokenId);
-        let encodedAssetData = Buffer.concat([encodedAddress, encodedTokenId]);
-        if (!_.isUndefined(receiverData)) {
-            const encodedReceiverData = ethUtil.toBuffer(receiverData);
-            const receiverDataLength = new BigNumber(encodedReceiverData.byteLength);
-            const encodedReceiverDataLength = assetProxyUtils.encodeUint256(receiverDataLength);
-            encodedAssetData = Buffer.concat([encodedAssetData, encodedReceiverDataLength, encodedReceiverData]);
-        }
-        encodedAssetData = Buffer.concat([encodedAssetData, encodedAssetProxyId]);
-        const encodedAssetDataHex = ethUtil.bufferToHex(encodedAssetData);
-        return encodedAssetDataHex;
+        // TODO: Pass `tokendId` as a BigNumber.
+        return ethUtil.bufferToHex(
+            ethAbi.simpleEncode(
+                'ERC721Token(address,uint256,bytes)',
+                tokenAddress,
+                `0x${tokenId.toString(constants.BASE_16)}`,
+                ethUtil.toBuffer(receiverData || '0x'),
+            ),
+        );
     },
     decodeERC721AssetData(assetData: string): ERC721AssetData {
-        const encodedAssetData = ethUtil.toBuffer(assetData);
-        if (encodedAssetData.byteLength < ERC721_ASSET_DATA_MINIMUM_BYTE_LENGTH) {
+        const data = ethUtil.toBuffer(assetData);
+        if (data.byteLength < constants.ERC721_ASSET_DATA_MINIMUM_BYTE_LENGTH) {
             throw new Error(
-                `Could not decode ERC20 Proxy Data. Expected length of encoded data to be at least 53. Got ${
-                    encodedAssetData.byteLength
-                }`,
+                `Could not decode ERC721 Asset Data. Expected length of encoded data to be at least ${
+                    constants.ERC721_ASSET_DATA_MINIMUM_BYTE_LENGTH
+                }. Got ${data.byteLength}`,
             );
         }
-
-        const encodedTokenAddress = encodedAssetData.slice(
-            ASSET_DATA_ADDRESS_OFFSET,
-            ERC721_ASSET_DATA_TOKEN_ID_OFFSET,
-        );
-        const proxyIdOffset = encodedAssetData.byteLength - 1;
-        const encodedAssetProxyId = encodedAssetData.slice(proxyIdOffset);
-        const assetProxyId = assetProxyUtils.decodeAssetProxyId(encodedAssetProxyId);
+        const assetProxyId = ethUtil.bufferToHex(data.slice(0, constants.SELECTOR_LENGTH));
         if (assetProxyId !== AssetProxyId.ERC721) {
             throw new Error(
-                `Could not decode ERC721 Proxy Data. Expected Asset Proxy Id to be ERC721 (${
+                `Could not decode ERC721 Asset Data. Expected Asset Proxy Id to be ERC721 (${
                     AssetProxyId.ERC721
                 }), but got ${assetProxyId}`,
             );
         }
-        const tokenAddress = assetProxyUtils.decodeAddress(encodedTokenAddress);
-        const encodedTokenId = encodedAssetData.slice(
-            ERC721_ASSET_DATA_TOKEN_ID_OFFSET,
-            ERC721_ASSET_DATA_RECEIVER_DATA_LENGTH_OFFSET,
+        const [tokenAddress, tokenId, receiverData] = ethAbi.rawDecode(
+            ['address', 'uint256', 'bytes'],
+            data.slice(constants.SELECTOR_LENGTH),
         );
-        const tokenId = assetProxyUtils.decodeUint256(encodedTokenId);
-        let receiverData = NULL_BYTES;
-        const lengthUpToReceiverDataLength = ERC721_ASSET_DATA_RECEIVER_DATA_LENGTH_OFFSET + 1;
-        if (encodedAssetData.byteLength > lengthUpToReceiverDataLength) {
-            const encodedReceiverDataLength = encodedAssetData.slice(
-                ERC721_ASSET_DATA_RECEIVER_DATA_LENGTH_OFFSET,
-                ERC721_ASSET_DATA_RECEIVER_DATA_OFFSET,
-            );
-            const receiverDataLength = assetProxyUtils.decodeUint256(encodedReceiverDataLength);
-            const lengthUpToReceiverData = ERC721_ASSET_DATA_RECEIVER_DATA_OFFSET + 1;
-            const expectedReceiverDataLength = new BigNumber(encodedAssetData.byteLength - lengthUpToReceiverData);
-            if (!receiverDataLength.equals(expectedReceiverDataLength)) {
-                throw new Error(
-                    `Data length (${receiverDataLength}) does not match actual length of data (${expectedReceiverDataLength})`,
-                );
-            }
-            const encodedReceiverData = encodedAssetData.slice(
-                ERC721_ASSET_DATA_RECEIVER_DATA_OFFSET,
-                receiverDataLength.add(ERC721_ASSET_DATA_RECEIVER_DATA_OFFSET).toNumber(),
-            );
-            receiverData = ethUtil.bufferToHex(encodedReceiverData);
-        }
-        const erc721AssetData: ERC721AssetData = {
+        return {
             assetProxyId,
-            tokenAddress,
-            tokenId,
-            receiverData,
+            tokenAddress: ethUtil.addHexPrefix(tokenAddress),
+            tokenId: new BigNumber(tokenId.toString()),
+            receiverData: ethUtil.bufferToHex(receiverData),
         };
-        return erc721AssetData;
     },
     decodeAssetDataId(assetData: string): AssetProxyId {
         const encodedAssetData = ethUtil.toBuffer(assetData);
-        if (encodedAssetData.byteLength < 1) {
+        if (encodedAssetData.byteLength < constants.SELECTOR_LENGTH) {
             throw new Error(
-                `Could not decode Proxy Data. Expected length of encoded data to be at least 1. Got ${
+                `Could not decode Proxy Data. Expected length of encoded data to be at least 4. Got ${
                     encodedAssetData.byteLength
                 }`,
             );
         }
-        const encodedAssetProxyId = encodedAssetData.slice(-1);
+        const encodedAssetProxyId = encodedAssetData.slice(0, constants.SELECTOR_LENGTH);
         const assetProxyId = assetProxyUtils.decodeAssetProxyId(encodedAssetProxyId);
         return assetProxyId;
     },
diff --git a/packages/order-utils/src/constants.ts b/packages/order-utils/src/constants.ts
index ed5bd8101..383a657b8 100644
--- a/packages/order-utils/src/constants.ts
+++ b/packages/order-utils/src/constants.ts
@@ -5,4 +5,10 @@ export const constants = {
     // tslint:disable-next-line:custom-no-magic-numbers
     UNLIMITED_ALLOWANCE_IN_BASE_UNITS: new BigNumber(2).pow(256).minus(1),
     TESTRPC_NETWORK_ID: 50,
+    ADDRESS_LENGTH: 20,
+    WORD_LENGTH: 32,
+    ERC20_ASSET_DATA_BYTE_LENGTH: 36,
+    ERC721_ASSET_DATA_MINIMUM_BYTE_LENGTH: 53,
+    SELECTOR_LENGTH: 4,
+    BASE_16: 16,
 };