Refactor event scraping and add support for scraping ERC20 approval events (#1401)

* Refactor event scraping and add support for scraping ERC20 approval events

* Add tests for data_sources/contract-wrappers/utils

1 files changed, 109 insertions, 0 deletions

diff --git a/packages/pipeline/test/data_sources/contract-wrappers/utils_test.ts b/packages/pipeline/test/data_sources/contract-wrappers/utils_test.ts
new file mode 100644
index 000000000..06f1a5e86
--- /dev/null
+++ b/packages/pipeline/test/data_sources/contract-wrappers/utils_test.ts
@@ -0,0 +1,109 @@
+// tslint:disable:custom-no-magic-numbers
+import * as chai from 'chai';
+import { LogWithDecodedArgs } from 'ethereum-types';
+import 'mocha';
+
+import { _getEventsWithRetriesAsync } from '../../../src/data_sources/contract-wrappers/utils';
+import { chaiSetup } from '../../utils/chai_setup';
+
+chaiSetup.configure();
+const expect = chai.expect;
+
+const retryableMessage = 'network timeout: (simulated network timeout error)';
+const retryableError = new Error(retryableMessage);
+
+describe('data_sources/contract-wrappers/utils', () => {
+    describe('_getEventsWithRetriesAsync', () => {
+        it('sends a single request if it was successful', async () => {
+            // Pre-declare values for the fromBlock and toBlock arguments.
+            const expectedFromBlock = 100;
+            const expectedToBlock = 200;
+            const expectedLogs: Array<LogWithDecodedArgs<any>> = [
+                {
+                    logIndex: 123,
+                    transactionIndex: 456,
+                    transactionHash: '0x6dd106d002873746072fc5e496dd0fb2541b68c77bcf9184ae19a42fd33657fe',
+                    blockHash: '0x6dd106d002873746072fc5e496dd0fb2541b68c77bcf9184ae19a42fd33657ff',
+                    blockNumber: 789,
+                    address: '0x6dd106d002873746072fc5e496dd0fb2541b68c77bcf9184ae19a42fd3365800',
+                    data: 'fake raw data',
+                    topics: [],
+                    event: 'TEST_EVENT',
+                    args: [1, 2, 3],
+                },
+            ];
+
+            // mockGetEventsAsync checks its arguments, increments `callCount`
+            // and returns `expectedLogs`.
+            let callCount = 0;
+            const mockGetEventsAsync = async (
+                fromBlock: number,
+                toBlock: number,
+            ): Promise<Array<LogWithDecodedArgs<any>>> => {
+                expect(fromBlock).equals(expectedFromBlock);
+                expect(toBlock).equals(expectedToBlock);
+                callCount += 1;
+                return expectedLogs;
+            };
+
+            // Make sure that we get what we expected and that the mock function
+            // was called exactly once.
+            const gotLogs = await _getEventsWithRetriesAsync(mockGetEventsAsync, 3, expectedFromBlock, expectedToBlock);
+            expect(gotLogs).deep.equals(expectedLogs);
+            expect(callCount).equals(
+                1,
+                'getEventsAsync function was called more than once even though it was successful',
+            );
+        });
+        it('retries and eventually succeeds', async () => {
+            const numRetries = 5;
+            let callCount = 0;
+            // mockGetEventsAsync throws unless callCount == numRetries + 1.
+            const mockGetEventsAsync = async (
+                _fromBlock: number,
+                _toBlock: number,
+            ): Promise<Array<LogWithDecodedArgs<any>>> => {
+                callCount += 1;
+                if (callCount === numRetries + 1) {
+                    return [];
+                }
+                throw retryableError;
+            };
+            await _getEventsWithRetriesAsync(mockGetEventsAsync, numRetries, 100, 300);
+            expect(callCount).equals(numRetries + 1, 'getEventsAsync function was called the wrong number of times');
+        });
+        it('throws for non-retryable errors', async () => {
+            const numRetries = 5;
+            const expectedMessage = 'Non-retryable error';
+            // mockGetEventsAsync always throws a non-retryable error.
+            const mockGetEventsAsync = async (
+                _fromBlock: number,
+                _toBlock: number,
+            ): Promise<Array<LogWithDecodedArgs<any>>> => {
+                throw new Error(expectedMessage);
+            };
+            // Note(albrow): This does actually return a promise (or at least a
+            // "promise-like object" and is a false positive in TSLint.
+            // tslint:disable-next-line:await-promise
+            await expect(_getEventsWithRetriesAsync(mockGetEventsAsync, numRetries, 100, 300)).to.be.rejectedWith(
+                expectedMessage,
+            );
+        });
+        it('throws after too many retries', async () => {
+            const numRetries = 5;
+            // mockGetEventsAsync always throws a retryable error.
+            const mockGetEventsAsync = async (
+                _fromBlock: number,
+                _toBlock: number,
+            ): Promise<Array<LogWithDecodedArgs<any>>> => {
+                throw retryableError;
+            };
+            // Note(albrow): This does actually return a promise (or at least a
+            // "promise-like object" and is a false positive in TSLint.
+            // tslint:disable-next-line:await-promise
+            await expect(_getEventsWithRetriesAsync(mockGetEventsAsync, numRetries, 100, 300)).to.be.rejectedWith(
+                retryableMessage,
+            );
+        });
+    });
+});