Add tryToDecodeLogOrNoOp and _getEventSignatureFromAbiByName on contract_wrapper

src/contract_wrappers/contract_wrapper.ts

@@ -1,13 +1,23 @@
 import * as _ from 'lodash';
 import * as Web3 from 'web3';
 import {Web3Wrapper} from '../web3_wrapper';
-import {ZeroExError, Artifact} from '../types';
+import {AbiDecoder} from '../utils/abi_decoder';
+import {ZeroExError, Artifact, LogWithDecodedArgs, RawLog, ContractEvents} from '../types';
 import {utils} from '../utils/utils';
 
 export class ContractWrapper {
     protected _web3Wrapper: Web3Wrapper;
-    constructor(web3Wrapper: Web3Wrapper) {
+    private _abiDecoder?: AbiDecoder;
+    constructor(web3Wrapper: Web3Wrapper, abiDecoder?: AbiDecoder) {
         this._web3Wrapper = web3Wrapper;
+        this._abiDecoder = abiDecoder;
+    }
+    protected tryToDecodeLogOrNoOp(log: Web3.LogEntry): LogWithDecodedArgs|RawLog {
+        if (_.isUndefined(this._abiDecoder)) {
+            throw new Error(ZeroExError.NoAbiDecoder);
+        }
+        const logWithDecodedArgs = this._abiDecoder.tryToDecodeLogOrNoOp(log);
+        return logWithDecodedArgs;
     }
     protected async _instantiateContractIfExistsAsync<A extends Web3.ContractInstance>(artifact: Artifact,
                                                                                        addressIfExists?: string,
@@ -16,4 +26,10 @@ export class ContractWrapper {
             await this._web3Wrapper.getContractInstanceFromArtifactAsync<A>(artifact, addressIfExists);
         return contractInstance;
     }
+    protected _getEventSignatureFromAbiByName(abi: Web3.ContractAbi, eventName: ContractEvents): string {
+        const eventAbi = _.filter(abi, {name: eventName})[0] as Web3.EventAbi;
+        const types = _.map(eventAbi.inputs, 'type');
+        const signature = `${eventAbi.name}(${types.join(',')})`;
+        return signature;
+    }
 }