1 files changed, 64 insertions, 2 deletions
diff --git a/src/contract_wrappers/contract_wrapper.ts b/src/contract_wrappers/contract_wrapper.ts
index 2a55b53d9..743dfc9b2 100644
--- a/src/contract_wrappers/contract_wrapper.ts
+++ b/src/contract_wrappers/contract_wrapper.ts
@@ -1,13 +1,52 @@
 import * as _ from 'lodash';
 import * as Web3 from 'web3';
+import * as ethUtil from 'ethereumjs-util';
 import {Web3Wrapper} from '../web3_wrapper';
-import {ZeroExError, Artifact} from '../types';
+import {AbiDecoder} from '../utils/abi_decoder';
+import {
+    InternalZeroExError,
+    Artifact,
+    LogWithDecodedArgs,
+    RawLog,
+    ContractEvents,
+    SubscriptionOpts,
+    IndexedFilterValues,
+} from '../types';
 import {utils} from '../utils/utils';
 
+const TOPIC_LENGTH = 32;
+
 export class ContractWrapper {
     protected _web3Wrapper: Web3Wrapper;
-    constructor(web3Wrapper: Web3Wrapper) {
+    private _abiDecoder?: AbiDecoder;
+    constructor(web3Wrapper: Web3Wrapper, abiDecoder?: AbiDecoder) {
         this._web3Wrapper = web3Wrapper;
+        this._abiDecoder = abiDecoder;
+    }
+    protected async _getLogsAsync(address: string, eventName: ContractEvents, subscriptionOpts: SubscriptionOpts,
+                                  indexFilterValues: IndexedFilterValues,
+                                  abi: Web3.ContractAbi): Promise<LogWithDecodedArgs[]> {
+        const eventAbi = _.find(abi, {name: eventName}) as Web3.EventAbi;
+        const eventSignature = this._getEventSignatureFromAbiByName(eventAbi, eventName);
+        const topicForEventSignature = this._web3Wrapper.keccak256(eventSignature);
+        const topicsForIndexedArgs = this._getTopicsForIndexedArgs(eventAbi, indexFilterValues);
+        const topics = [topicForEventSignature, ...topicsForIndexedArgs];
+        const filter = {
+            fromBlock: subscriptionOpts.fromBlock,
+            toBlock: subscriptionOpts.toBlock,
+            address,
+            topics,
+        };
+        const logs = await this._web3Wrapper.getLogsAsync(filter);
+        const logsWithDecodedArguments = _.map(logs, this._tryToDecodeLogOrNoop.bind(this));
+        return logsWithDecodedArguments;
+    }
+    protected _tryToDecodeLogOrNoop(log: Web3.LogEntry): LogWithDecodedArgs|RawLog {
+        if (_.isUndefined(this._abiDecoder)) {
+            throw new Error(InternalZeroExError.NoAbiDecoder);
+        }
+        const logWithDecodedArgs = this._abiDecoder.tryToDecodeLogOrNoop(log);
+        return logWithDecodedArgs;
     }
     protected async _instantiateContractIfExistsAsync<A extends Web3.ContractInstance>(artifact: Artifact,
                                                                                        addressIfExists?: string,
@@ -16,4 +55,27 @@ export class ContractWrapper {
             await this._web3Wrapper.getContractInstanceFromArtifactAsync<A>(artifact, addressIfExists);
         return contractInstance;
     }
+    protected _getEventSignatureFromAbiByName(eventAbi: Web3.EventAbi, eventName: ContractEvents): string {
+        const types = _.map(eventAbi.inputs, 'type');
+        const signature = `${eventAbi.name}(${types.join(',')})`;
+        return signature;
+    }
+    private _getTopicsForIndexedArgs(abi: Web3.EventAbi, indexFilterValues: IndexedFilterValues): Array<string|null> {
+        const topics: Array<string|null> = [];
+        for (const eventInput of abi.inputs) {
+            if (!eventInput.indexed) {
+                continue;
+            }
+            if (_.isUndefined(indexFilterValues[eventInput.name])) {
+                topics.push(null);
+            } else {
+                const value = indexFilterValues[eventInput.name] as string;
+                const buffer = ethUtil.toBuffer(value);
+                const paddedBuffer = ethUtil.setLengthLeft(buffer, TOPIC_LENGTH);
+                const topic = ethUtil.bufferToHex(paddedBuffer);
+                topics.push(topic);
+            }
+        }
+        return topics;
+    }
 }