From 1ea272600c16ef4ace69c9c0564798d8821a6d7e Mon Sep 17 00:00:00 2001
From: Cadence Ember <cadence@disroot.org>
Date: Sat, 3 Oct 2020 01:32:22 +1300
Subject: [PATCH] Handle empty subscription queue and OOP-ify

---
 api/subscriptions.js      |  3 ++
 background/feed-update.js | 87 +++++++++++++++++++++++++--------------
 utils/constants.js        |  8 ++++
 3 files changed, 67 insertions(+), 31 deletions(-)

diff --git a/api/subscriptions.js b/api/subscriptions.js
index ef1d8c5..80beaaa 100644
--- a/api/subscriptions.js
+++ b/api/subscriptions.js
@@ -3,6 +3,7 @@ const db = require("../utils/db")
 const {fetchChannelLatest} = require("../utils/youtube")
 const {getUser} = require("../utils/getuser")
 const {timeToPastText} = require("../utils/converters")
+const {refresher} = require("../background/feed-update")
 
 module.exports = [
 	{
@@ -13,6 +14,8 @@ module.exports = [
 			let channels = []
 			let refreshed = null
 			if (user.token) {
+				// trigger a background refresh, needed if they came back from being inactive
+				refresher.skipWaiting()
 				// get channels
 				const subscriptions = user.getSubscriptions()
 				const template = Array(subscriptions.length).fill("?").join(", ")
diff --git a/background/feed-update.js b/background/feed-update.js
index cacc72d..3de5edd 100644
--- a/background/feed-update.js
+++ b/background/feed-update.js
@@ -61,43 +61,68 @@ class RefreshQueue {
 	}
 }
 
-const refreshQueue = new RefreshQueue()
+class Refresher {
+	constructor() {
+		this.sym = constants.symbols.refresher
+		this.refreshQueue = new RefreshQueue()
+		this.state = this.sym.ACTIVE
+		this.waitingTimeout = null
+		this.next()
+	}
 
-function refreshChannel(ucid) {
-	return fetch(`http://localhost:3000/api/v1/channels/${ucid}/latest`).then(res => res.json()).then(root => {
-		if (Array.isArray(root)) {
-			root.forEach(video => {
-				// organise
-				video.descriptionHtml = video.descriptionHtml.replace(/<a /g, '<a tabindex="-1" ') // should be safe
-				video.viewCountText = null //TODO?
-				// store
-				prepared.video_insert.run(video)
-			})
-			// update channel refreshed
-			prepared.channel_refreshed_update.run(Date.now(), ucid)
-			console.log(`updated ${root.length} videos for channel ${ucid}`)
-		} else if (root.identifier === "PUBLISHED_DATES_NOT_PROVIDED") {
-			return [] // nothing we can do. skip this iteration.
-		} else {
-			throw new Error(root.error)
+	refreshChannel(ucid) {
+		return fetch(`http://localhost:3000/api/v1/channels/${ucid}/latest`).then(res => res.json()).then(root => {
+			if (Array.isArray(root)) {
+				root.forEach(video => {
+					// organise
+					video.descriptionHtml = video.descriptionHtml.replace(/<a /g, '<a tabindex="-1" ') // should be safe
+					video.viewCountText = null //TODO?
+					// store
+					prepared.video_insert.run(video)
+				})
+				// update channel refreshed
+				prepared.channel_refreshed_update.run(Date.now(), ucid)
+				console.log(`updated ${root.length} videos for channel ${ucid}`)
+			} else if (root.identifier === "PUBLISHED_DATES_NOT_PROVIDED") {
+				return [] // nothing we can do. skip this iteration.
+			} else {
+				throw new Error(root.error)
+			}
+		})
+	}
+
+	next() {
+		if (this.refreshQueue.isEmpty()) {
+			const timeSinceLastLoop = Date.now() - this.refreshQueue.lastLoadTime
+			if (timeSinceLastLoop < constants.caching.subscriptions_refresh_loop_min) {
+				const timeToWait = constants.caching.subscriptions_refresh_loop_min - timeSinceLastLoop
+				console.log(`waiting ${timeToWait} before next loop`)
+				this.state = this.sym.WAITING
+				this.waitingTimeout = setTimeout(() => this.next(), timeToWait)
+				return
+			} else {
+				this.refreshQueue.load()
+			}
 		}
-	})
-}
 
-function refreshNext() {
-	if (refreshQueue.isEmpty()) {
-		const timeSinceLastLoop = Date.now() - refreshQueue.lastLoadTime
-		if (timeSinceLastLoop < constants.caching.subscriptions_refresh_loop_min) {
-			const timeToWait = constants.caching.subscriptions_refresh_loop_min - timeSinceLastLoop
-			console.log(`waiting ${timeToWait} before next loop`)
-			return setTimeout(refreshNext, timeToWait)
+		if (!this.refreshQueue.isEmpty()) {
+			this.state = this.sym.ACTIVE
+			const ucid = this.refreshQueue.next()
+			this.refreshChannel(ucid).then(() => this.next())
 		} else {
-			refreshQueue.load()
+			this.state = this.sym.EMPTY
 		}
 	}
 
-	const ucid = refreshQueue.next()
-	refreshChannel(ucid).then(refreshNext)
+	skipWaiting() {
+		if (this.state !== this.sym.ACTIVE) {
+			clearTimeout(this.waitingTimeout)
+			this.refreshQueue.lastLoadTime = 0
+			this.next()
+		}
+	}
 }
 
-refreshNext()
+const refresher = new Refresher()
+
+module.exports.refresher = refresher
diff --git a/utils/constants.js b/utils/constants.js
index 88bdc32..4625208 100644
--- a/utils/constants.js
+++ b/utils/constants.js
@@ -19,6 +19,14 @@ const constants = {
 	regex: {
 		ucid: "[A-Za-z0-9-_]+",
 		video_id: "[A-Za-z0-9-_]+"
+	},
+
+	symbols: {
+		refresher: {
+			ACTIVE: Symbol("ACTIVE"),
+			WAITING: Symbol("WAITING"),
+			EMPTY: Symbol("EMPTY")
+		}
 	}
 }