Refactorized PriceFetcher + Strategy class hierarchy

backend/main.ts

@@ -0,0 +1,12 @@
+/**
+ * Pricecaster Service.
+ *
+ * Fetcher backend component.
+ *
+ * (c) 2021 Randlabs, Inc.
+ */
+
+import { PriceFetcher } from './pricefetch'
+
+const pricefetcher = new PriceFetcher()
+pricefetcher.run()

backend/pricefetch.ts

@@ -1,24 +1,69 @@
+/**
+ * Pricecaster Service.
+ *
+ * Fetcher backend component.
+ *
+ * (c) 2021 Randlabs, Inc.
+ */
+
 import { getPythProgramKeyForCluster, PriceData, Product, PythConnection } from '@pythnetwork/client'
-import {Cluster, clusterApiUrl, Connection, PublicKey} from '@solana/web3.js'
+import { Cluster, clusterApiUrl, Connection } from '@solana/web3.js'
+import algosdk from 'algosdk'
+const PricecasterLib = require('../lib/pricecaster')
+const settings = require('../settings')
 
-const SOLANA_CLUSTER_NAME: Cluster = 'devnet'
-const connection = new Connection(clusterApiUrl(SOLANA_CLUSTER_NAME))
-const pythPublicKey = getPythProgramKeyForCluster(SOLANA_CLUSTER_NAME)
+/**
+ * The main Price fetcher service class.
+ */
+export class PriceFetcher {
+  private pclib: any
+  pythConnection: PythConnection
 
-const algosdk = require('algosdk')
+  constructor () {
+    const SOLANA_CLUSTER_NAME: Cluster = settings.pyth.solanaClusterName as Cluster
+    const connection = new Connection(clusterApiUrl(SOLANA_CLUSTER_NAME))
+    const pythPublicKey = getPythProgramKeyForCluster(SOLANA_CLUSTER_NAME)
+    const algodClient = new algosdk.Algodv2(settings.token, settings.api, settings.port)
+    this.pythConnection = new PythConnection(connection, pythPublicKey)
+    this.pclib = new PricecasterLib.PricecasterLib(algodClient)
+  }
 
+  /**
+   * Starts the service.
+   */
+  run () {
+    console.log('Pricecaster Service Fetcher  -- (c) 2021 Randlabs.io\n')
+    console.log('AlgoClient Configuration: ')
+    console.log(`API: '${settings.api}' PORT:'${settings.port}'`)
 
-
-const pythConnection = new PythConnection(connection, pythPublicKey)
-pythConnection.onPriceChange((product: Product, price: PriceData) => {
-    if (product.symbol == 'BTC/USD') {
-        // sample output:
-        // SRM/USD: $8.68725 ±$0.0131
-        // tslint:disable-next-line:no-console
-        console.log(`${product.symbol}: $${price.price} \xB1$${price.confidence}`)
+    if (this.preflightCheck()) {
+      console.log('Preflight check passed, starting Pyth listener...')
+      this.pythConnection.start()
+      this.pythConnection.onPriceChange((product: Product, price: PriceData) => {
+        this.onPriceChange(product, price)
+      })
     }
-})
 
-// tslint:disable-next-line:no-console
-console.log("Reading from Pyth price feed...")
-pythConnection.start()
+    console.log('Booting done.')
+  }
+
+  /**
+   * Executes a preflight check of configuration parameters.
+   * @returns True if parameters are ok, false otherwise.
+   */
+  preflightCheck () {
+    return true
+  }
+
+  /**
+   * Price reception handler.
+   * @param product The reported symbol/pair
+   * @param price The reported price data
+   */
+  onPriceChange (product: Product, price: PriceData) {
+    // eslint-disable-next-line no-prototype-builtins
+    if (settings.symbols.hasOwnProperty(product.symbol)) {
+      console.log(`${product.symbol}: $${price.price} \xB1$${price.confidence}`)
+    }
+  }
+}

backend/strategy.ts

@@ -0,0 +1,38 @@
+/**
+ * Pricecaster Service.
+ *
+ * Fetcher backend component.
+ *
+ * (c) 2021 Randlabs, Inc.
+ */
+
+import { PriceData } from '@pythnetwork/client'
+
+/**
+ * Implements a strategy for obtaining an asset price from
+ * a set of received prices in a buffer.
+ */
+export interface IStrategy {
+    /**
+     *
+     * @param size The size of the buffer
+     */
+    createBuffer(size: number): void
+
+    /**
+     * Clear price buffer
+     */
+    clearBuffer(): void
+
+    /**
+     * Put a new price in buffer.
+     * @param priceData  The price data to put
+     * @returns true if successful.
+     */
+    put(priceData: PriceData): boolean
+
+    /**
+     * Get the calculated price according to selected strategy.
+     */
+    getPrice(): number
+}

backend/strategyAvgPrice.ts

@@ -0,0 +1,15 @@
+/**
+ * Pricecaster Service.
+ *
+ * Fetcher backend component.
+ *
+ * (c) 2021 Randlabs, Inc.
+ */
+
+import { StrategyBaseQueue } from './strategyqueuebase'
+
+class StrategyAveragePrice extends StrategyBaseQueue {
+  getPrice (): number {
+    return 0
+  }
+}

backend/strategyBase.ts

@@ -0,0 +1,23 @@
+/**
+ * Pricecaster Service.
+ *
+ * Fetcher backend component.
+ *
+ * (c) 2021 Randlabs, Inc.
+ */
+
+import { PriceData } from '@pythnetwork/client'
+import { IStrategy } from './strategy'
+
+export abstract class StrategyBase implements IStrategy {
+    protected symbol: string
+    constructor (symbol: string, bufSize: number) {
+      this.symbol = symbol
+      this.createBuffer(bufSize)
+    }
+
+    abstract put(priceData: PriceData): boolean
+    abstract createBuffer(size: number): void
+    abstract clearBuffer(): void
+    abstract getPrice(): number
+}

backend/strategyQueueBase.ts

@@ -0,0 +1,36 @@
+/**
+ * Pricecaster Service.
+ *
+ * Fetcher backend component.
+ *
+ * (c) 2021 Randlabs, Inc.
+ */
+
+import { PriceData } from '@pythnetwork/client'
+import { StrategyBase } from './strategyBase'
+
+/**
+ * A base class for queue-based buffer strategies
+ */
+export abstract class StrategyBaseQueue extends StrategyBase {
+  private buffer: PriceData[]
+  private bufSize: number
+
+  createBuffer (maxSize: number): void {
+    this.bufSize = maxSize
+  }
+
+  clearBuffer (): void {
+    this.buffer.length = 0
+  }
+
+  put (priceData: PriceData): boolean {
+    if (this.buffer.length === this.bufSize) {
+      this.buffer.shift()
+    }
+    this.buffer.push(priceData)
+    return true
+  }
+
+  abstract getPrice(): number
+}

lib/pricecaster.d.ts

@@ -0,0 +1 @@
+declare module 'PricecasterLib';

package.json

@@ -4,7 +4,7 @@
   "description": "Experimentation with pyth",
   "main": "index.js",
   "scripts": {
-    "start": "npx ts-node backend/pricefetch.ts",
+    "start": "npx ts-node backend/main.ts",
     "test": "mocha --timeout 60000"
   },
   "author": "",

settings.js

@@ -1,13 +1,26 @@
 module.exports = {
+  pyth: {
+    solanaClusterName: 'devnet'
+  },
   token: '',
   api: 'https://api.betanet.algoexplorer.io',
   port: '',
-  'BTC/USD': {
-    appId: 3020301,
-    verifierpk: 'OPDM7ACAW64Q4VBWAL77Z5SHSJVZZ44V3BAN7W44U43SUXEOUENZMZYOQU',
-    buffersize: 50,
-    ratio: 'asap',
-    strategy: 'maxconf',
-    phony: false
+  symbols: {
+    'BTC/USD': {
+      appId: 3020301,
+      verifierpk: 'OPDM7ACAW64Q4VBWAL77Z5SHSJVZZ44V3BAN7W44U43SUXEOUENZMZYOQU',
+      buffersize: 50,
+      ratio: 'asap',
+      strategy: 'maxconf',
+      phony: false
+    },
+    'ETH/USD': {
+      appId: 3020301,
+      verifierpk: 'OPDM7ACAW64Q4VBWAL77Z5SHSJVZZ44V3BAN7W44U43SUXEOUENZMZYOQU',
+      buffersize: 50,
+      ratio: 'asap',
+      strategy: 'maxconf',
+      phony: false
+    }
   }
 }