fix(@embark/blockchain-api): add back contract event listen and log

Adds back the watch on contract events and writes them to a file
with the same method as contract logs from transaction-logger, so
I extracted those methods to utils/file so that both could use the
same functions.

Author: jrainville

dapps/templates/demo/contracts/simple_storage.sol

@@ -3,12 +3,15 @@ pragma solidity ^0.6.0;
 contract SimpleStorage {
   uint public storedData;
 
+  event Set(address caller, uint _value);
+
   constructor(uint initialValue) public {
     storedData = initialValue;
   }
 
   function set(uint x) public {
     storedData = x;
+    emit Set(msg.sender, x);
   }
 
   function get() public view returns (uint retVal) {

packages/cockpit/ui/src/actions/index.js

@@ -180,7 +180,7 @@ export const contractLogs = {
 export const CONTRACT_EVENTS = createRequestTypes('CONTRACT_EVENTS');
 export const contractEvents = {
   request: () => action(CONTRACT_EVENTS[REQUEST]),
-  success: (contractEvents) => action(CONTRACT_EVENTS[SUCCESS], {contractEvents}),
+  success: (contractEvents) => action(CONTRACT_EVENTS[SUCCESS], {contractEvents: contractEvents ? contractEvents.reverse() : []}),
   failure: (error) => action(CONTRACT_EVENTS[FAILURE], {error, name: 'contractEvents'})
 };
 

packages/core/utils/src/file.ts

@@ -1,9 +1,11 @@
+import { Logger } from 'embark-logger';
 import { __ } from 'embark-i18n';
 import * as fs from 'fs-extra';
 import * as path from 'path';
 import { downloadFile } from './network';
 import { dappPath, embarkPath } from './pathUtils';
 import { ImportRemapping, prepareForCompilation } from './solidity/remapImports';
+import { cargo } from 'async';
 
 const HTTP_CONTRACTS_DIRECTORY = '.embark/contracts/';
 
@@ -179,3 +181,53 @@ export function getExternalContractUrl(file: string, providerUrl: string) {
     url,
   };
 }
+
+export function  getCircularReplacer() {
+  const seen = new WeakSet();
+  return (key, value) => {
+    if (typeof value === "object" && value !== null) {
+      if (seen.has(value)) {
+        return;
+      }
+      seen.add(value);
+    }
+    return value;
+  };
+}
+
+export function getAppendLogFileCargo(logFilePath: string, logger: Logger) {
+  return cargo((tasks, callback) => {
+    let appendThis = '';
+    tasks.forEach(task => {
+      // Write each line to a JSON string. The replacer is to avoid circular dependencies
+      // Add a comma at the end to be able to make an array off of it when reading
+      appendThis += `${JSON.stringify(task, getCircularReplacer())},\n`;
+    });
+    fs.appendFile(logFilePath, appendThis, (err) => {
+      if (err) {
+        logger.error('Error writing to the log file', err.message);
+        logger.trace(err);
+      }
+      callback();
+    });
+  });
+}
+
+export async function readAppendedLogs(logFile: string, asString: boolean = false) {
+  await fs.ensureFile(logFile);
+  const data = await fs.readFile(logFile);
+
+  let stringData = data.toString();
+
+  if (!stringData) {
+    return asString ? '[]' : [];
+  }
+
+  // remove last comma and add brackets around to make it an array of object logs
+  stringData = `[${stringData.substring(0, stringData.length - 2)}]`;
+  if (asString) {
+    return stringData;
+  }
+
+  return JSON.parse(stringData);
+}

packages/core/utils/src/index.ts

@@ -59,7 +59,7 @@ const { extendZeroAddressShorthand, replaceZeroAddressShorthand } = AddressUtils
 
 export { compact, last, recursiveMerge, groupBy } from './collections';
 export { prepareForCompilation } from './solidity/remapImports';
-export { File, getExternalContractUrl, Types } from './file';
+export { File, getExternalContractUrl, Types, getAppendLogFileCargo, getCircularReplacer, readAppendedLogs } from './file';
 
 export {
   findMonorepoPackageFromRoot,

packages/plugins/ethereum-blockchain-client/src/api.js

@@ -1,5 +1,5 @@
 import async from "async";
-import {dappPath} from 'embark-utils';
+import {dappPath, getAppendLogFileCargo, readAppendedLogs} from 'embark-utils';
 const embarkJsUtils = require('embarkjs').Utils;
 const {bigNumberify} = require('ethers/utils/bignumber');
 const RLP = require('ethers/utils/rlp');
@@ -11,11 +11,20 @@ const BLOCK_LIMIT = 100;
 export default class EthereumAPI {
   constructor(embark, web3, blockchainName) {
     this.embark = embark;
+    this.events = embark.events;
+    this.logger = embark.logger;
     this.blockchainName = blockchainName;
     this.web3 = web3;
     this.requestManager = new Manager(web3.currentProvider);
     this.fs = embark.fs;
-    this.logFile = dappPath(".embark", "contractEvents.json");
+    this.logFile = dappPath(".embark", "contractEvents.json.txt");
+    this.contractsSubscriptions = [];
+    this.contractsEvents = [];
+
+    this.writeLogFile = getAppendLogFileCargo(this.logFile, this.logger);
+    this.events.on('contractsDeployed', () => {
+      this.subscribeToContractEvents();
+    });
   }
 
   registerAPIs() {
@@ -26,7 +35,7 @@ export default class EthereumAPI {
     this.embark.events.request("blockchain:api:register", this.blockchainName, "getTransactions", this.getTransactions.bind(this));
     this.embark.events.request("blockchain:api:register", this.blockchainName, "getTransactionByHash", this.getTransactionByHash.bind(this));
     this.embark.events.request("blockchain:api:register", this.blockchainName, "getTransactionByRawTransactionHash", this.getTransactionByRawTransactionHash.bind(this));
-    this.embark.events.request("blockchain:api:register", this.blockchainName, "getEvents", this.getEvents.bind(this));
+    this.embark.events.request("blockchain:api:register", this.blockchainName, "getEvents", this.readEvents.bind(this));
     this.embark.events.request("blockchain:api:register", this.blockchainName, "signMessage", this.signMessage.bind(this));
     this.embark.events.request("blockchain:api:register", this.blockchainName, "verifyMessage", this.verifyMessage.bind(this));
   }
@@ -356,7 +365,7 @@ export default class EthereumAPI {
       });
   }
 
-  subscribeToContractEvents(callback) {
+  subscribeToContractEvents() {
     this.contractsSubscriptions.forEach((eventEmitter) => {
       const reqMgr = eventEmitter.options.requestManager;
       // attempting an eth_unsubscribe when not connected throws an
@@ -378,28 +387,24 @@ export default class EthereumAPI {
         eventEmitter.on('data', (data) => {
           const dataWithName = Object.assign(data, {name: contractObject.className});
           this.contractsEvents.push(dataWithName);
+          this.saveEvent(dataWithName);
           this.events.emit('blockchain:contracts:event', dataWithName);
         });
       });
-      callback();
     });
   }
 
-  getEvents() {
-    const data = this.readEvents();
-    return Object.values(data).reverse();
-  }
-
   saveEvent(event) {
     this.writeLogFile.push(event);
   }
 
-  readEvents() {
-    this.fs.ensureFileSync(this.logFile);
+  async readEvents(asString) {
     try {
-      return JSON.parse(this.fs.readFileSync(this.logFile));
-    } catch (_error) {
-      return {};
+      return readAppendedLogs(this.logFile, asString);
+    } catch (e) {
+      this.logger.error('Error reading contract log file', e.message);
+      this.logger.trace(e.trace);
+      return asString ? '[]' : [];
     }
   }
 

packages/plugins/ethereum-blockchain-client/src/index.js

@@ -15,8 +15,6 @@ class EthereumBlockchainClient {
     this.events = embark.events;
     this.logger = embark.logger;
     this.fs = embark.fs;
-    this.contractsSubscriptions = [];
-    this.contractsEvents = [];
 
     this.logFile = dappPath(".embark", "contractEvents.json");
 

packages/plugins/transaction-logger/src/index.js

@@ -1,10 +1,9 @@
-const async = require('async');
 import { __ } from 'embark-i18n';
 const Web3 = require('web3');
 const util = require('util');
 
 const { blockchain: blockchainConstants } = require('embark-core/constants');
-import { dappPath, hexToNumber } from 'embark-utils';
+import { dappPath, hexToNumber, getAppendLogFileCargo, readAppendedLogs } from 'embark-utils';
 import { getAddressToContract, getTransactionParams } from './transactionUtils';
 export { getAddressToContract, getTransactionParams };
 
@@ -18,19 +17,6 @@ const LISTENED_METHODS = [
   blockchainConstants.transactionMethods.eth_sendRawTransaction
 ];
 
-const getCircularReplacer = () => {
-  const seen = new WeakSet();
-  return (key, value) => {
-    if (typeof value === "object" && value !== null) {
-      if (seen.has(value)) {
-        return;
-      }
-      seen.add(value);
-    }
-    return value;
-  };
-};
-
 export default class TransactionLogger {
   constructor(embark, _options) {
     this.embark = embark;
@@ -60,21 +46,7 @@ export default class TransactionLogger {
       });
     });
 
-    this.writeLogFile = async.cargo((tasks, callback) => {
-      let appendThis = '';
-      tasks.forEach(task => {
-        // Write each line to a JSON string. The replacer is to avoid circular dependencies
-        // Add a comma at the end to be able to make an array off of it when reading
-        appendThis += `${JSON.stringify(task, getCircularReplacer())},\n`;
-      });
-      this.fs.appendFile(this.logFile, appendThis, (err) => {
-        if (err) {
-          this.logger.error('Error writing to the log file', err.message);
-          this.logger.trace(err);
-        }
-        callback();
-      });
-    });
+    this.writeLogFile = getAppendLogFileCargo(this.logFile, this.logger);
   }
 
   get web3() {
@@ -272,25 +244,10 @@ export default class TransactionLogger {
 
   async _readLogs(asString = false) {
     try {
-      await this.fs.ensureFile(this.logFile);
-      let data = await this.fs.readFile(this.logFile);
-
-      data = data.toString();
-
-      if (!data) {
-        return asString ? '[]' : [];
-      }
-
-      // remove last comma and add brackets around to make it an array of object logs
-      data = `[${data.substring(0, data.length - 2)}]`;
-      if (asString) {
-        return data;
-      }
-
-      return JSON.parse(data);
-    } catch (error) {
-      this.logger.error('Error reading contract log file', error.message);
-      this.logger.trace(error.trace);
+      return readAppendedLogs(this.logFile, asString);
+    } catch (e) {
+      this.logger.error('Error reading contract log file', e.message);
+      this.logger.trace(e.trace);
       return asString ? '[]' : [];
     }
   }

packages/stack/blockchain/src/api.ts

@@ -248,10 +248,10 @@ export default class BlockchainAPI {
     this.embark.registerAPICall(
       "get",
       "/embark-api/blockchain/contracts/events",
-      (_req, res) => {
+      async (_req, res) => {
         try {
           const getEvents = this.getCallForBlockchain(blockchainName, "getEvents");
-          res.send(JSON.stringify(getEvents()));
+          res.send(await getEvents(true));
         } catch (error) {
           res.status(500).send({ error });
         }