From 0c98930d4cb2aa7e5d4a14e6d2e411288a6b08b8 Mon Sep 17 00:00:00 2001
From: Nick Krecklow <hello@github.nklow.com>
Date: Mon, 11 May 2020 18:44:29 -0500
Subject: [PATCH] centralize timestamp/point filtering, move magic numbers into
 named constants

---
 lib/app.js      |  2 +-
 lib/database.js |  2 +-
 lib/ping.js     |  2 +-
 lib/servers.js  | 15 ++-------------
 lib/time.js     | 39 +++++++++++++++++++++++++--------------
 5 files changed, 30 insertions(+), 30 deletions(-)

diff --git a/lib/app.js b/lib/app.js
index 8f8b924..c4419b3 100644
--- a/lib/app.js
+++ b/lib/app.js
@@ -2,7 +2,7 @@ const Database = require('./database')
 const MojangUpdater = require('./mojang')
 const PingController = require('./ping')
 const Server = require('./server')
-const TimeTracker = require('./time')
+const { TimeTracker } = require('./time')
 const MessageOf = require('./message')
 
 const config = require('../config')
diff --git a/lib/database.js b/lib/database.js
index c54bfb7..3e22245 100644
--- a/lib/database.js
+++ b/lib/database.js
@@ -1,6 +1,6 @@
 const sqlite = require('sqlite3')
 
-const TimeTracker = require('./time')
+const { TimeTracker } = require('./time')
 
 class Database {
   constructor (app) {
diff --git a/lib/ping.js b/lib/ping.js
index a91e92a..a830207 100644
--- a/lib/ping.js
+++ b/lib/ping.js
@@ -3,7 +3,7 @@ const minecraftBedrockPing = require('mcpe-ping-fixed')
 
 const logger = require('./logger')
 const MessageOf = require('./message')
-const TimeTracker = require('./time')
+const { TimeTracker } = require('./time')
 
 const { getPlayerCountOrNull } = require('./util')
 
diff --git a/lib/servers.js b/lib/servers.js
index f400368..fc28cdd 100644
--- a/lib/servers.js
+++ b/lib/servers.js
@@ -1,7 +1,7 @@
 const crypto = require('crypto')
 const dns = require('dns')
 
-const TimeTracker = require('./time')
+const { GRAPH_UPDATE_TIME_GAP, TimeTracker } = require('./time')
 const Server = require('./server')
 
 const { getPlayerCountOrNull } = require('./util')
@@ -124,18 +124,7 @@ class ServerRegistration {
   }
 
   loadGraphPoints (startTime, timestamps, points) {
-    // Filter pings so each result is a minute apart
-    let lastTimestamp = startTime
-
-    for (let i = 0; i < timestamps.length; i++) {
-      const timestamp = timestamps[i]
-
-      if (timestamp - lastTimestamp >= 60 * 1000) {
-        lastTimestamp = timestamp
-
-        this.graphData.push(points[i])
-      }
-    }
+    this.graphData = TimeTracker.everyN(timestamps, startTime, GRAPH_UPDATE_TIME_GAP, (i) => points[i])
   }
 
   findNewGraphPeak () {
diff --git a/lib/time.js b/lib/time.js
index f810ac4..0165215 100644
--- a/lib/time.js
+++ b/lib/time.js
@@ -1,5 +1,7 @@
 const config = require('../config.json')
 
+const GRAPH_UPDATE_TIME_GAP = 60 * 1000 // 60 seconds
+
 class TimeTracker {
   constructor (app) {
     this._app = app
@@ -14,7 +16,7 @@ class TimeTracker {
 
     // Flag each group as history graph additions each minute
     // This is sent to the frontend for graph updates
-    const updateHistoryGraph = config.logToDatabase && (!this._lastHistoryGraphUpdate || timestamp - this._lastHistoryGraphUpdate >= 60 * 1000)
+    const updateHistoryGraph = config.logToDatabase && (!this._lastHistoryGraphUpdate || timestamp - this._lastHistoryGraphUpdate >= GRAPH_UPDATE_TIME_GAP)
 
     if (updateHistoryGraph) {
       this._lastHistoryGraphUpdate = timestamp
@@ -31,18 +33,8 @@ class TimeTracker {
 
   loadGraphPoints (startTime, timestamps) {
     // This is a copy of ServerRegistration#loadGraphPoints
-    // relativeGraphData contains original timestamp data and needs to be filtered into minutes
-    let lastTimestamp = startTime
-
-    for (let i = 0; i < timestamps.length; i++) {
-      const timestamp = timestamps[i]
-
-      if (timestamp - lastTimestamp >= 60 * 1000) {
-        lastTimestamp = timestamp
-
-        this._graphPoints.push(timestamp)
-      }
-    }
+    // timestamps contains original timestamp data and needs to be filtered into minutes
+    this._graphPoints = TimeTracker.everyN(timestamps, startTime, GRAPH_UPDATE_TIME_GAP, (i) => timestamps[i])
   }
 
   getGraphPointAt (i) {
@@ -69,6 +61,22 @@ class TimeTracker {
     return Math.ceil(config.graphDuration / config.rates.pingAll)
   }
 
+  static everyN (array, start, diff, adapter) {
+    const selected = []
+    let lastPoint = start
+
+    for (let i = 0; i < array.length; i++) {
+      const point = array[i]
+
+      if (point - lastPoint >= diff) {
+        lastPoint = point
+        selected.push(adapter(i))
+      }
+    }
+
+    return selected
+  }
+
   static pushAndShift (array, value, maxLength) {
     array.push(value)
 
@@ -78,4 +86,7 @@ class TimeTracker {
   }
 }
 
-module.exports = TimeTracker
+module.exports = {
+  GRAPH_UPDATE_TIME_GAP,
+  TimeTracker
+}