4 files changed, 78 insertions, 1 deletions
diff --git a/packages/utils/package.json b/packages/utils/package.json
index a1cf4c24a..db82f8040 100644
--- a/packages/utils/package.json
+++ b/packages/utils/package.json
@@ -20,15 +20,18 @@
     "homepage": "https://github.com/0xProject/0x.js/packages/utils/README.md",
     "devDependencies": {
         "@0xproject/tslint-config": "^0.4.5",
+        "@0xproject/types": "^0.1.5",
         "@types/lodash": "^4.14.86",
         "npm-run-all": "^4.1.2",
         "shx": "^0.2.2",
         "tslint": "5.8.0",
+        "web3-typescript-typings": "^0.9.5",
         "typescript": "~2.6.1"
     },
     "dependencies": {
         "bignumber.js": "~4.1.0",
         "js-sha3": "^0.7.0",
-        "lodash": "^4.17.4"
+        "lodash": "^4.17.4",
+        "web3": "^0.20.0"
     }
 }
diff --git a/packages/utils/src/abi_decoder.ts b/packages/utils/src/abi_decoder.ts
new file mode 100644
index 000000000..f96ee2edb
--- /dev/null
+++ b/packages/utils/src/abi_decoder.ts
@@ -0,0 +1,70 @@
+import { AbiType, DecodedLogArgs, LogWithDecodedArgs, RawLog, SolidityTypes } from '@0xproject/types';
+import * as _ from 'lodash';
+import * as Web3 from 'web3';
+import * as SolidityCoder from 'web3/lib/solidity/coder';
+
+import { BigNumber } from './configured_bignumber';
+
+export class AbiDecoder {
+    private _savedABIs: Web3.AbiDefinition[] = [];
+    private _methodIds: { [signatureHash: string]: Web3.EventAbi } = {};
+    private static _padZeros(address: string) {
+        let formatted = address;
+        if (_.startsWith(formatted, '0x')) {
+            formatted = formatted.slice(2);
+        }
+
+        formatted = _.padStart(formatted, 40, '0');
+        return `0x${formatted}`;
+    }
+    constructor(abiArrays: Web3.AbiDefinition[][]) {
+        _.map(abiArrays, this._addABI.bind(this));
+    }
+    // This method can only decode logs from the 0x & ERC20 smart contracts
+    public tryToDecodeLogOrNoop<ArgsType>(log: Web3.LogEntry): LogWithDecodedArgs<ArgsType> | RawLog {
+        const methodId = log.topics[0];
+        const event = this._methodIds[methodId];
+        if (_.isUndefined(event)) {
+            return log;
+        }
+        const logData = log.data;
+        const decodedParams: DecodedLogArgs = {};
+        let dataIndex = 0;
+        let topicsIndex = 1;
+
+        const nonIndexedInputs = _.filter(event.inputs, input => !input.indexed);
+        const dataTypes = _.map(nonIndexedInputs, input => input.type);
+        const decodedData = SolidityCoder.decodeParams(dataTypes, logData.slice('0x'.length));
+
+        _.map(event.inputs, (param: Web3.EventParameter) => {
+            // Indexed parameters are stored in topics. Non-indexed ones in decodedData
+            let value: BigNumber | string = param.indexed ? log.topics[topicsIndex++] : decodedData[dataIndex++];
+            if (param.type === SolidityTypes.Address) {
+                value = AbiDecoder._padZeros(new BigNumber(value).toString(16));
+            } else if (
+                param.type === SolidityTypes.Uint256 ||
+                param.type === SolidityTypes.Uint8 ||
+                param.type === SolidityTypes.Uint
+            ) {
+                value = new BigNumber(value);
+            }
+            decodedParams[param.name] = value;
+        });
+
+        return {
+            ...log,
+            event: event.name,
+            args: decodedParams,
+        };
+    }
+    private _addABI(abiArray: Web3.AbiDefinition[]): void {
+        _.map(abiArray, (abi: Web3.AbiDefinition) => {
+            if (abi.type === AbiType.Event) {
+                const signature = `${abi.name}(${_.map(abi.inputs, input => input.type).join(',')})`;
+                const signatureHash = new Web3().sha3(signature);
+                this._methodIds[signatureHash] = abi;
+            }
+        });
+        this._savedABIs = this._savedABIs.concat(abiArray);
+    }
+}
diff --git a/packages/utils/src/globals.d.ts b/packages/utils/src/globals.d.ts
new file mode 100644
index 000000000..ade9e59db
--- /dev/null
+++ b/packages/utils/src/globals.d.ts
@@ -0,0 +1,3 @@
+declare module 'web3/lib/solidity/coder' {
+    const decodeParams: (types: string[], data: string) => any[];
+}
diff --git a/packages/utils/src/index.ts b/packages/utils/src/index.ts
index 2768e49ab..39dede41f 100644
--- a/packages/utils/src/index.ts
+++ b/packages/utils/src/index.ts
@@ -3,3 +3,4 @@ export { addressUtils } from './address_utils';
 export { classUtils } from './class_utils';
 export { intervalUtils } from './interval_utils';
 export { BigNumber } from './configured_bignumber';
+export { AbiDecoder } from './abi_decoder';