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Using a Local RSS File as My Notification System

2024-06-08 - [53] 3:20

Recently, "Garage: Bad Dream Adventure" came out on the Nintendo Switch eShop for $24.99 USD, as opposed to its $19.90 USD price on steam or $4.99 USD price on the Apple app store and Google Play. Considering how generally niche this game is, I suspect it will go on sale at some point on the Nintendo eShop. I wanted to write a quick program that can scrape the page on nintendo.com to see if a sale is happening and how long the sale is going on for. Not just for this game, but potentially for other games I might have my eye on as well. Building that web page scraper was relatively straight forward for me, but I needed to solve another problem... How do I get that information in front of me so I am made aware of it?

There are a few things I check on my computer nearly every day, and sometimes multiple times a day. One of those things would be email. Initially I wanted to have my program email me when it detects specific sales, but I didn't really feel like dealing with spam filters to make sure the emails come through for me to see. Another thing I check often enough is my RSS feed reader. That's what I decided to build these notifications for.

Turns out it's really easy for the RSS feed reader I use, newsboat, to load a local RSS feed file. Newsboat also has good RSS feed item caching, where it uses the value of guid to determine if a new RSS feed item is available so newsboat can tell me that there's a new RSS feed item. I use the SHA256 hash of the RSS feed item description (the content) as for the guid value, which means newsboat will only show me that there's a new feed item when it hasn't seen that exact description before.

There are only 2 cases where the guid will match a different RSS feed item in the newsboat cache:

In both of these cases, I'm not alerted more than once by newsboat, as long as I don't clear the newsboat cache. This means I can rewrite the RSS feed file as many times as I want. I also only need to use a single RSS feed item for the feed file.

I'm pretty sure I will end up using this idea again of having a local RSS feed file for notifications I should see in the future.

Below is an example RSS feed file created by my Nintendo eShop scraping program:

<?xml version="1.0" encoding="utf-8" ?>
<rss version="2.0">
<channel>
	<title>Nintendo eShop Sales</title>
	<link>http://localhost</link>
	<description>Self-generated RSS feed to show Nintendo eShop sales</description>
	<item>
		<title>Current Nintendo eShop Sales</title>
		<link>http://localhost</link>
		<guid>4d06bc884c45a764cafe019706d9a509aab59fa1dc79d51aee4e07e0fa7e1a22</guid>
		<pubDate>Sat, 08 Jun 2024 02:28:47 +0000</pubDate>
		<description><![CDATA[<h1>Current Nintendo eShop Sales</h1>

<h2>Mysterious Retro Games Bundle</h2>
<p>Current Price: $1.99 USD (80% Off)
<br>
Normal Price: $9.99 USD
<br>
Sale Ends: Jun 24, 2024 06:59 UTC
<br>
<a href="https://www.nintendo.com/us/store/products/mysterious-retro-games-bundle-switch/" target="_blank">eShop Page</a></p>

<h2>The Last Campfire</h2>
<p>Current Price: $1.99 USD (86% Off)
<br>
Normal Price: $14.99 USD
<br>
Sale Ends: Jun 11, 2024 06:59 UTC
<br>
<a href="https://www.nintendo.com/us/store/products/the-last-campfire-switch/" target="_blank">eShop Page</a></p>
]]></description>
	</item>
</channel>
</rss>

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