1 files changed, 95 insertions, 0 deletions
diff --git a/packages/contract-wrappers/src/utils/filter_utils.ts b/packages/contract-wrappers/src/utils/filter_utils.ts
new file mode 100644
index 000000000..c5df7321e
--- /dev/null
+++ b/packages/contract-wrappers/src/utils/filter_utils.ts
@@ -0,0 +1,95 @@
+import {
+    ConstructorAbi,
+    ContractAbi,
+    EventAbi,
+    FallbackAbi,
+    FilterObject,
+    LogEntry,
+    MethodAbi,
+} from '@0xproject/types';
+import * as ethUtil from 'ethereumjs-util';
+import * as jsSHA3 from 'js-sha3';
+import * as _ from 'lodash';
+import * as uuid from 'uuid/v4';
+
+import { BlockRange, ContractEvents, IndexedFilterValues } from '../types';
+
+const TOPIC_LENGTH = 32;
+
+export const filterUtils = {
+    generateUUID(): string {
+        return uuid();
+    },
+    getFilter(
+        address: string,
+        eventName: ContractEvents,
+        indexFilterValues: IndexedFilterValues,
+        abi: ContractAbi,
+        blockRange?: BlockRange,
+    ): FilterObject {
+        const eventAbi = _.find(abi, { name: eventName }) as EventAbi;
+        const eventSignature = filterUtils.getEventSignatureFromAbiByName(eventAbi, eventName);
+        const topicForEventSignature = ethUtil.addHexPrefix(jsSHA3.keccak256(eventSignature));
+        const topicsForIndexedArgs = filterUtils.getTopicsForIndexedArgs(eventAbi, indexFilterValues);
+        const topics = [topicForEventSignature, ...topicsForIndexedArgs];
+        let filter: FilterObject = {
+            address,
+            topics,
+        };
+        if (!_.isUndefined(blockRange)) {
+            filter = {
+                ...blockRange,
+                ...filter,
+            };
+        }
+        return filter;
+    },
+    getEventSignatureFromAbiByName(eventAbi: EventAbi, eventName: ContractEvents): string {
+        const types = _.map(eventAbi.inputs, 'type');
+        const signature = `${eventAbi.name}(${types.join(',')})`;
+        return signature;
+    },
+    getTopicsForIndexedArgs(abi: 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])) {
+                // Null is a wildcard topic in a JSON-RPC call
+                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;
+    },
+    matchesFilter(log: LogEntry, filter: FilterObject): boolean {
+        if (!_.isUndefined(filter.address) && log.address !== filter.address) {
+            return false;
+        }
+        if (!_.isUndefined(filter.topics)) {
+            return filterUtils.matchesTopics(log.topics, filter.topics);
+        }
+        return true;
+    },
+    matchesTopics(logTopics: string[], filterTopics: Array<string[] | string | null>): boolean {
+        const matchesTopic = _.zipWith(logTopics, filterTopics, filterUtils.matchesTopic.bind(filterUtils));
+        const matchesTopics = _.every(matchesTopic);
+        return matchesTopics;
+    },
+    matchesTopic(logTopic: string, filterTopic: string[] | string | null): boolean {
+        if (_.isArray(filterTopic)) {
+            return _.includes(filterTopic, logTopic);
+        }
+        if (_.isString(filterTopic)) {
+            return filterTopic === logTopic;
+        }
+        // null topic is a wildcard
+        return true;
+    },
+};