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Creating a Social Media Website with Pure Magic

It might be tempting to believe that Magic is only for CRUD HTTP REST endpoints. However, Magic and Hyperlambda makes it possible to create anything you can create in any other programming languages. In this tutorial, we will look at one specific use case, and create a backend for a Social Media website, similar to Reddit in functionality. You can download the backend at its GitHub project website. In the below video you can see me demonstrate the system, how to install it, and its basic structure. Watch the video first, and then let’s go over some of its key concepts.

Key points from the system

AnarQ does a lot beyond simple CRUD. For instance, it sends emails, it creates database transactions, it returns graph objects back to the client as JSON, it creates joins from multiple tables as it is executing SQL, etc. So let’s look at some of its key points, since it demonstrates the capacity of Hyperlambda and Magic.

SQL Joins

If you look at the “feed” endpoint’s code, you will see that it creates fairly rich and complex SQL joins. Below is a part of its code.

What the above code basically does, is to join the posts table with the likes table, grouping by post IDs, and returning an aggregate result of the number of likes a post have, for then to order descendingly on number of likes a post has. A simple little trick that allows us to retrieve the most popular posts first, effectively becoming the ghist of the algorithm from Reddit, that ensures the most popular posts are listed at the top of its “feed”.

In addition it filters out everything older than some threshold amount of time, implying over time, posts will “drop out” of the feed, depending upon what range you invoke the endpoint with. For instance, if you set its [minutes] argument to 60, it will only return posts that was posted less that 60 minutes ago, yet still order such that posts with the most likes ends up being returned first.

Sending emails

Typically you want users to confirm their email address as they’re registering. This creates a bit more accountability, resulting in hopefully increasing the quality of what people post. Magic contains one slot that significantly simplifies this for us, which is consumed in AnarQ as follows.

What the above basically does, is to send a “template email”. A template email is an email where you have template fields, that has variables that are dynamically substituted with some sort of arguments. Such template emails in magic are simple files, typically HTML files, containing dynamically substituted portions, such as the email below illustrates with its {{confirm-url}} part.

The actual value of the {{confirm-url}} again, is passed in as [substitutes]/[confirm-url]. The [magic.emails.send] dynamic slot again, will then create a personalised email, by substituting whatever you pass in as substitutes with its template placeholder such as illustrated above. Of course, in order to actually send emails though, you’ll need to configure an SMTP server, which is typically done by adding something such as the following to your “appsettings.json” file.

The above configuration is how it would typically look like if you’re using SendGrid, but Magic supports any SMTP server you wish.

Returning files

Another interesting thing AnarQ does is to return contents of files. For instance the terms and conditions to use AnarQ is actually just a Markdown file, wrapped inside an endpoint, such that the terms can easily be modified according to your needs, allowing the endpoint that returns the terms immediately return whatever terms you want your users to agree to before signing up. Below is the endpoint in its entirety to illustrate one way you could return a file’s content directly to the caller over a Hyperlambda endpoint.

What the above does is simply to load the “tnc.md” file, add some HTTP caching, and return the file as is to the caller.

Database transactions

AnarQ requires database transactions in one place, which is when a comment it created. This is because the database actually implements something referred to as “materialised path”, allowing us to store data being a relational tree structure into an SQL database. However, in order to accomplish this, we need to first insert our comment, retrieve its automatically assigned ID, for then to afterwards update the post. During this process we need atomicity, since if something goes wrong, we don’t want _any_ changes to our database. You can see the relevant code in the “comment.post.hl” file, but its most important parts can be found below, which is the part that creates the transaction.

Dynamic Hyperlambda slots

AnarQ also creates its own dynamic Hyperlambda slots. This occurs in its “magic.startup” folder, who’s name is important, since folders with that exact name inside of modules will have all Hyperlambda files automatically executed during installation, and/or startup. If you check out the file caller “anarq.emails.comment-received.hl”, you will see some code resembling the following.

What this file does is to create a dynamic slot that simply make sure as somebody is commenting on a post, the original poster is notified through emails, unless he’s turned off email notifications.

Dynamically creating its database

In addition, AnarQ also automatically creates its database during initialisation. This is done in its “create-database.hl” file, also inside of its “magic.startup” folder, which implies the file will always execute as Magic is started, and/or the module is initialised. You can probably get a lot of ideas from that specific file in regards to how you’d like to achieve something similar in your own apps.

Wrapping up

In this tutorial we looked at some of the basic elements of AnarQ, to illustrate that Magic is more than CRUD. If you want to download AnarQ and install in your own Magic server, you can find it below.

Notice, as I wrote this article, I used AnarQ version 0.8, and I might expand on the project in the future – Implying some of the specific parts we walked through here might change in a future version of AnarQ. Have that in mind if you’re dissecting a newer version than what I showed you in this article.

Credit: Source link

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