Fluid – decentralized twitter-like feed built on Fluence with SQLite

Workshop

Step 0 – Framework

Here you can see the most basic Fluence app – just a hello-world.

Take a note of #invocation_handler macro, it marks function as an entry-point to your app.

Step 1 – JSON API

Now let's define some API for our feed backend. Let's use JSON as a communication format, and serde_json Rust library for handy serialization and deserialization.

Two enums – Request and Response in api.rs describe API for interaction with frontend.

Method parse parses Request from JSON, and serialize converts Response back to JSON string, so it can be returned to frontend.

Here we also define model.rs – that's how we plan to use our database. Currently it is just a prototype, so we can implement our API in it's full.

Step 2 – Database

Let's forget for a moment about API, and dive into using SQLite module.

ffi.rs describes inter-module communication between Fluid and SQLite
databse.rs provides us with query function that executes SQL query on SQLite module, and returns result as a String

Now, take a look at lib.rs – a few SQL requests are sent there.

First one creates the table for messages, next goes message insertion, emulating a user who's creating a post. Then, we select all messages and log them.

But we decided to use JSON as a communication format, and SQLite allows us to query results in json. So the last query does exactly that – it is the same as usual SELECT *, but wraps result in json array.

Step 3 – Tying everything together

Now let's use our SQLite knowledge to implement model.rs so our API can really persists and read data. And voilà, we have our backend for almost twitter, but it can be easily decentralized!

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