feat(ref-imp): #989 - added event emitter support

lib/bitcoin/BitcoinClient.ts

@@ -718,6 +718,7 @@ export default class BitcoinClient {
   private static createBitcoinOutputModel (bitcoreOutput: Transaction.Output): BitcoinOutputModel {
     return {
       satoshis: bitcoreOutput.satoshis,
+      // Some transaction outputs do not have a script, such as coinbase transactions.
       scriptAsmAsString: bitcoreOutput.script ? bitcoreOutput.script.toASM() : ''
     };
   }
@@ -742,7 +743,6 @@ export default class BitcoinClient {
 
   private async getUnspentOutputs (address: Address): Promise<Transaction.UnspentOutput[]> {
 
-    // Retrieve all transactions by addressToSearch via BCoin Node API /tx/address/$address endpoint
     const addressToSearch = address.toString();
     Logger.info(`Getting unspent coins for ${addressToSearch}`);
     const request = {

lib/common/EventEmitter.ts

@@ -0,0 +1,31 @@
+import IEventEmitter from './interfaces/IEventEmitter';
+import LogColor from './LogColor';
+
+/**
+ * Event emitter used in Sidetree.
+ * Intended to be machine readable for triggering custom handlers.
+ */
+export default class EventEmitter {
+  // Default to basic console log.
+  private static singleton: IEventEmitter = {
+    emit: async (eventCode) => {
+      console.log(LogColor.lightBlue(`Event emitted: ${LogColor.green(eventCode)}`));
+    }
+  };
+
+  /**
+   * Overrides the default event emitter if given.
+   */
+  static initialize (customEventEmitter?: IEventEmitter) {
+    if (customEventEmitter !== undefined) {
+      EventEmitter.singleton = customEventEmitter;
+    }
+  }
+
+  /**
+   * Emits an event.
+   */
+  public static async emit (eventName: string, eventData?: {[property: string]: any}): Promise<void> {
+    await EventEmitter.singleton.emit(eventName, eventData);
+  }
+}

lib/common/Logger.ts

@@ -3,6 +3,7 @@ import ILogger from './interfaces/ILogger';
 
 /**
  * Logger used in Sidetree.
+ * Intended to be human readable for debugging.
  */
 export default class Logger {
   private static singleton: ILogger = new ConsoleLogger();

lib/common/interfaces/IEventEmitter.ts

@@ -0,0 +1,9 @@
+/**
+ * Custom event emitter interface.
+ */
+export default interface IEventEmitter {
+  /**
+   * Emits an event.
+   */
+  emit (eventName: string, eventData?: {[property: string]: any}): Promise<void>;
+}

lib/common/interfaces/ILogger.ts

@@ -1,5 +1,5 @@
 /**
- * Logging interface used in Sidetree.
+ * Custom logger interface.
  */
 export default interface ILogger {
   /**

lib/core/BatchScheduler.ts

@@ -1,4 +1,6 @@
 import * as timeSpan from 'time-span';
+import EventCode from './EventCode';
+import EventEmitter from '../common/EventEmitter';
 import IBlockchain from './interfaces/IBlockchain';
 import IVersionManager from './interfaces/IVersionManager';
 import Logger from '../common/Logger';
@@ -50,6 +52,8 @@ export default class BatchScheduler {
       const batchWriter = this.versionManager.getBatchWriter(currentTime);
 
       await batchWriter.write();
+
+      EventEmitter.emit(EventCode.BatchWriterProcessingLoopSuccess);
     } catch (error) {
       Logger.error('Unexpected and unhandled error during batch writing, investigate and fix:');
       Logger.error(error);

lib/core/Core.ts

@@ -1,9 +1,10 @@
 import * as timeSpan from 'time-span';
-import { ISidetreeCas, ISidetreeLogger } from '..';
+import { ISidetreeCas, ISidetreeEventEmitter, ISidetreeLogger } from '..';
 import BatchScheduler from './BatchScheduler';
 import Blockchain from './Blockchain';
 import Config from './models/Config';
 import DownloadManager from './DownloadManager';
+import EventEmitter from '../common/EventEmitter';
 import LogColor from '../common/LogColor';
 import Logger from '../common/Logger';
 import MongoDbOperationStore from './MongoDbOperationStore';
@@ -66,8 +67,9 @@ export default class Core {
    * The initialization method that must be called before consumption of this core object.
    * The method starts the Observer and Batch Writer.
    */
-  public async initialize (customLogger?: ISidetreeLogger) {
+  public async initialize (customLogger?: ISidetreeLogger, customEventEmitter?: ISidetreeEventEmitter) {
     Logger.initialize(customLogger);
+    EventEmitter.initialize(customEventEmitter);
 
     // DB initializations.
     await this.serviceStateStore.initialize();

lib/core/EventCode.ts

@@ -0,0 +1,7 @@
+/**
+ * Event codes used by Sidetree core service.
+ */
+export default {
+  BatchWriterProcessingLoopSuccess: 'batch_writer_processing_loop_success',
+  ObserverProcessingLoopSuccess: 'observer_processing_loop_success'
+};

lib/core/Observer.ts

@@ -1,5 +1,7 @@
 import * as timeSpan from 'time-span';
 import TransactionUnderProcessingModel, { TransactionProcessingStatus } from './models/TransactionUnderProcessingModel';
+import EventCode from './EventCode';
+import EventEmitter from '../common/EventEmitter';
 import IBlockchain from './interfaces/IBlockchain';
 import IOperationStore from './interfaces/IOperationStore';
 import ITransactionProcessor from './interfaces/ITransactionProcessor';
@@ -121,7 +123,7 @@ export default class Observer {
 
         // NOTE: Blockchain reorg has happened for sure only if `invalidTransactionNumberOrTimeHash` AND
         // latest transaction time is less or equal to blockchain service time.
-        // This check will prevent Core from reverting transactions if/when blockchain service is reinitializing its data itself.
+        // This check will prevent Core from reverting transactions if/when blockchain service is re-initializing its data itself.
         let blockReorganizationDetected = false;
         if (invalidTransactionNumberOrTimeHash) {
           if (lastKnownTransactionTime <= this.blockchain.approximateTime.time) {
@@ -161,6 +163,8 @@ export default class Observer {
 
       // Continue onto processing unresolvable transactions if any.
       await this.processUnresolvableTransactions();
+
+      EventEmitter.emit(EventCode.ObserverProcessingLoopSuccess);
     } catch (error) {
       Logger.error(`Encountered unhandled and possibly fatal Observer error, must investigate and fix:`);
       Logger.error(error);

lib/index.ts

@@ -3,6 +3,7 @@
 import ISidetreeBitcoinConfig from './bitcoin/IBitcoinConfig';
 import ISidetreeBitcoinWallet from './bitcoin/interfaces/IBitcoinWallet';
 import ISidetreeCas from './core/interfaces/ICas';
+import ISidetreeEventEmitter from './common/interfaces/IEventEmitter';
 import ISidetreeLogger from './common/interfaces/ILogger';
 import SidetreeBitcoinProcessor from './bitcoin/BitcoinProcessor';
 import SidetreeBitcoinVersionModel from './bitcoin/models/BitcoinVersionModel';
@@ -32,5 +33,6 @@ export {
 
 // Common exports.
 export {
+  ISidetreeEventEmitter,
   ISidetreeLogger
 };

package.json

@@ -100,7 +100,8 @@
       "lib/bitcoin/versions/[0-9]**/**",
       "lib/core/versions/[0-9]**/**",
       "lib/core/versions/**/VersionMetadata.ts",
-      "lib/**/**ErrorCode.ts"
+      "lib/**/**ErrorCode.ts",
+      "lib/**/**EventCode.ts"
     ],
     "reporter": [
       "text",

tests/core/Core.spec.ts

@@ -1,5 +1,6 @@
 import Config from '../../lib/core/models/Config';
 import Core from '../../lib/core/Core';
+import EventEmitter from '../../lib/common/EventEmitter';
 import IRequestHandler from '../../lib/core/interfaces/IRequestHandler';
 import Logger from '../../lib/common/Logger';
 import MockCas from '../mocks/MockCas';
@@ -58,7 +59,7 @@ describe('Core', async () => {
       expect(downloadManagerStartSpy).toHaveBeenCalled();
     });
 
-    it('should override the default logger if custom logger is given.', async () => {
+    it('should override the default logger/event emitter if custom logger/event emitter is given.', async () => {
       const core = new Core(testConfig, testVersionConfig, mockCas);
 
       spyOn(core['serviceStateStore'], 'initialize');
@@ -75,17 +76,26 @@ describe('Core', async () => {
 
       let customLoggerInvoked = false;
       const customLogger = {
-        info: (_data: any) => { customLoggerInvoked = true; },
-        warn: (_data: any) => { },
-        error: (_data: any) => { }
+        info: () => { customLoggerInvoked = true; },
+        warn: () => { },
+        error: () => { }
       };
 
-      await core.initialize(customLogger);
+      let customEvenEmitterInvoked = false;
+      const customEvenEmitter = {
+        emit: async () => { customEvenEmitterInvoked = true; }
+      };
+
+      await core.initialize(customLogger, customEvenEmitter);
 
       // Invoke logger to trigger the custom logger's method defined above.
       Logger.info('anything');
 
+      // Invoke event emitter to trigger the custom emitter's method defined above.
+      await EventEmitter.emit('anything');
+
       expect(customLoggerInvoked).toBeTruthy();
+      expect(customEvenEmitterInvoked).toBeTruthy();
     });
 
     it('should not start the Batch Writer and Observer if they are disabled.', async () => {