1 files changed, 39 insertions, 0 deletions
diff --git a/packages/contracts/src/utils/log_decoder.ts b/packages/contracts/src/utils/log_decoder.ts
new file mode 100644
index 000000000..747c7644d
--- /dev/null
+++ b/packages/contracts/src/utils/log_decoder.ts
@@ -0,0 +1,39 @@
+import { ContractArtifact } from '@0xproject/sol-compiler';
+import { AbiDefinition, LogEntry, LogWithDecodedArgs, RawLog } from '@0xproject/types';
+import { AbiDecoder, BigNumber } from '@0xproject/utils';
+import * as _ from 'lodash';
+
+import { artifacts } from './artifacts';
+
+export class LogDecoder {
+    private _abiDecoder: AbiDecoder;
+    constructor(networkIdIfExists?: number) {
+        if (_.isUndefined(networkIdIfExists)) {
+            throw new Error('networkId not specified');
+        }
+        const abiArrays: AbiDefinition[][] = [];
+        _.forEach(artifacts, (artifact: ContractArtifact) => {
+            const compilerOutput = artifact.compilerOutput;
+            abiArrays.push(compilerOutput.abi);
+        });
+        this._abiDecoder = new AbiDecoder(abiArrays);
+    }
+    public decodeLogOrThrow<ArgsType>(log: LogEntry): LogWithDecodedArgs<ArgsType> | RawLog {
+        const logWithDecodedArgsOrLog = this._abiDecoder.tryToDecodeLogOrNoop(log);
+        if (_.isUndefined((logWithDecodedArgsOrLog as LogWithDecodedArgs<ArgsType>).args)) {
+            throw new Error(`Unable to decode log: ${JSON.stringify(log)}`);
+        }
+        wrapLogBigNumbers(logWithDecodedArgsOrLog);
+        return logWithDecodedArgsOrLog;
+    }
+}
+
+function wrapLogBigNumbers(log: any): any {
+    const argNames = _.keys(log.args);
+    for (const argName of argNames) {
+        const isWeb3BigNumber = _.startsWith(log.args[argName].constructor.toString(), 'function BigNumber(');
+        if (isWeb3BigNumber) {
+            log.args[argName] = new BigNumber(log.args[argName]);
+        }
+    }
+}