Learn Clojure, Http and Xstate

Astro is a flexible web framework that allows you to build fast websites to suit your needs.

By default, Astro will build your site using Static Site Generation (SSG). This means the data in your site is loaded at build time so that the end-user gets served static pages that load quickly.

While Astro defaults this way, it also has Server-Side Rendering (SSR) that you can enable if you have more serverful needs in your application.

Along similar lines, Astro utilizes HTML and the browser as a default but when you need more flexibility you can opt into an Astro Island. Islands use React, Vue, Angular, or any frontend JavaScript framework you are used to enhance the user experience in your site.

astro

Now that we have our database set up, we need to use it!

On our blog post page, we have a likes button waiting for us to implement the likes feature. On page load, we'll make a fetch call to a `/api/likes/[slug].ts` GET end point to return the number of likes for the page. 

Similarly, when someone clicks the like button we want to send a POST request to that same endpoint.

On the server side we will set up `GET` and `POST` handlers to implement this functionality. In those functions we'll use Drizzle to return the likes for that blog post and in the case of a `POST` we'll create a record if it doesn't exist or increment a like if it does and return.

Astro API endpoints utilize browser `Response` API so you'll get a chance to handle returning different status's based on the data present.

Create Astro API Endpoints to Get and Update Database Records using Drizzle ORM

Jotai's state management is primitive and flexible. This gives you room to build, compose, and share state throughout your application exactly how you need it.

This flexibility can become hard to manage when you have complex requirements that span across a number of states your application can be in.

Jotai lets you leverage other state management solutions through integrations so that you can solve the problem you're facing exactly how you need to.

One of those integrations is XState. XState gives you a safe abstraction to enumerate and handle the complex states your application can be in.

With Jotai + XState, you get the flexibility and ease of use of Jotai with the power of XState.

XState is a sophisticated library to provide a better and safer abstraction for state management. 

React is one of the web’s most popular frameworks for building JavaScript applications. 

If you know what you’re doing, React can drastically simplify how you build, use, and maintain code.

Whether you’re a React newbie or you’re ready for advanced techniques, you can level-up with egghead. Explore our in-depth courses, lessons, and community resources to build more powerful applications and crack open your career.

react

Complex State Management in React with Jotai and XState

Statecharts are a formalism for modeling stateful, reactive systems. This is useful for declaratively describing the behavior of your application, from the individual components to the overall application logic.

xstate

Sometimes adding initial values through the jotai Provider is not what you want. Provider will create a whole new store with atom values

One way to initialize a state machine inside Jotai is to turn our initial `lightAtom` into a function `createLightAtom`. This function will take an `initial` property that we can pass to `createLightMachine` when we declare the function. We will then useEffect to initialize our lightMachine.

There is a small limitation with this pattern, the machine is initialized with it's default value and then over ridden with the value we pass in the effect. The initial render will use that default value while the second render will have the value we passed in.


Initialize a Xstate Machine with Jotai Atom in Atom Pattern

We currently have a machine that displays a circle of green. When you click it, it will cycle through green, yellow, and Red.

What if you wanted to pass XState initial values from Jotai, you'll need to use the `initialValues` prop on Jotai Provider and pass a list of pair (atom and value) to it.

To do this we'll refactor the creation of the lightMachine to be a function that accepts an atom as an initial value.

One note to be aware of is that this initial value will only be set when the XState machines instantiate.


Provide XState with Initial Values through Jotai Provider

Sometimes you need to display values in specific ways throughout your application based on the state that you are managing. The way to do this is to derive your state so you don't have to track multiple stateful items.

In Jotai, this is accomplished by creating an atom, getting the value from another atom that you are managing (in this case from Xstate), and using that value how you need it in your derived atom. This atom will be re-evaluated every time the managed state changes.

This pattern is great to use if you have complex state managed in something like Xstate but need a derived state value that is not strongly tied to that managed state. The pattern works the same for async and synchronous function calls as well as pulling in multiple atoms and libraries to use in your derived state.


Derive Jotai Atom State from Complex State Managed in Xstate 

Jotai has a primitive and flexible API, because of this it's up to you on how you manage your state within an atom. 

Sometimes your state is complex enough to warrant a sophisticated library for safer abstraction. This is where you can install xstate to your application and Jotai will work seamlessly with the state machines that you define using `atomWithMachine`.

This allows you to consume the machine like any other atom in your components with `useAtom`. 

As an added bonus, I'll show you how to use xstate's visualizer to develop and interact with your state machine in dev tools. 


Handle Complex State in Jotai with XState using atomWithMachine

The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. It is a generic, stateless, protocol which can be used for many tasks beyond its use for hypertext, such as name servers and distributed object management systems, through extension of its request methods, error codes and headers.

http

We're adding Github authorization to our client app

Create a function that is called on window load. In that function store the parameters that get sent over to the Github auth server. 

In our query params, we will set the response_type parameter to "code" in order to ask the auth server for a code. Asking for a code from the auth server is more secure than asking for the access token through a browser

Finally, create a URL from the params and an authorization endpoint. Using a query selector select an anchor tag and set the href attribute to the URL that you created.

Add GitHub Authorization to an OAuth Client App

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

express

We'll create our client-server using the `express` and `cors` packages

Express will be used to create our HTTP application. We'll need it to post to our endpoints and listen to our port.

We need the `cors` package to make cross-origin requests since the front-end will be a different origin than the server.

Create an OAuth Client-Server for code/token exchange

We'll be parsing the authorization code sent in our query before sending it to the server.

We do this by creating a function that parses our query and retrieves the code parameter. If we find a code in the query we send the code to our server by using `fetch` to make a `POST` request. In the body of the request we send the code and the state in stringified JSON.

Once we make the request we can await a response and store its JSON data (the auth token) in a variable. In a real application, we might also redirect to the homepage or the page the user was just on.

Parse for the Auth Code in a Query before Sending It to a Server

We're going to refactor some of our HTTP application code in order to create the ability to exchange the code inside our HTTP request for a token. 

We can do this by creating a function that takes the code from a request and posts a query that contains our client id and secret to our token endpoint. We then await a response, parse the data from the response, and then return the parsed data.

Exchange Auth Code in a Request for an Access Token

We're going to fetch a user with that token we exchanged the code parameter for in the previous lesson. 

All we have to do is make a fetch request to the `/user` endpoint with an Authorization header that contains the token and then return the data. Like this ``Authorization: `Bearer ${token}``

Fetch Protected Data from a Resource Server with an Access Token

 Every developer who has attempted to demystify OAuth 2.0 must be presented with mind-bugging complicated flow diagrams. It becomes worse when you try to understand all the terminologies of OAuth 2.0 and Open ID protocols.

There is no getting around the OAuth 2.0 flow being complicated with back and forth between your browser, the service you are authenticating with, and the application you want to access. 

This course gets straight to the point without any application code distracting you from the core takeaway -- You will learn how to authenticate and authorize yourself using GitHub as your Auth Server.

We'll first cover the OAuth 2.0 flow for authentication and then integrate the Open ID protocol for authorization.

[**LIVE EVENT**: Register here for a live webinar with Christian on OAuth.](https://egghead.zoom.us/webinar/register/WN_Sxy1FEcoTea8UA6F7EDzLw) Bring any questions you have from taking this course!

JSON Web Tokens are an open, industry standard RFC 7519 method for representing claims securely between two parties.

Add Github Login to Your Web App with OAuth 2.0

Joel and David chat about the big ideas and the essential questions of State Management and State Machines. Additionally, David also gives a walkthrough of XState, XState Visualizer, and the upcoming dev tools for XState.

## Key Terms

**XState -** is a library for creating, interpreting, and executing finite state machines and statecharts, as well as managing invocations of those machines as actors.

**State Machines** - a mathematical model of computation. It is an abstract machine that can be in exactly one of a finite number of states at any given time.

**Combinatorial Explosion -**  is the rapid growth of the complexity of a problem.

## Resources

- [davidkpiano/xstate](https://github.com/davidkpiano/xstate)

- [David K. 🎹](https://twitter.com/DavidKPiano)

- [davidkpiano - Overview](https://github.com/davidkpiano)

- [Stately Newsletter](https://www.stately.dev)

## Visuals Explanation

![](https://res.cloudinary.com/dg3gyk0gu/image/upload/v1618253832/transcript-images/state-management-2021-descriptions/state-machine-states-events-transitions-actions.jpg)

Source: [https://www.stately.dev](https://www.stately.dev/)

**These notes include:** highlights, expansion of key terms, code blocks, and links to additional resources. **They follow the same structure as the recording.**

## What are the big ideas of State Management?

- It all comes down to applying big ideas from the past, for example, State Machines.
- One of the biggest problems related to State Machines is performance.
- The problems with States are not new.

## Why is this hard to understand these problems?

- **There's a mathematical explication to this.** Once you have more than one piece of State in different places, you faced Combinatorial Explosion.
- **Combinatorial Explosion**

    A combinatorial explosion is the rapid growth of the complexity of a problem due to how the combinatorics of the problem is affected by the input, constraints, and bounds of the problem.

    Combinatorics is an area of mathematics primarily concerned with counting, both as a means and an end in obtaining results.

- An example of this is having ten main ingredients and having the output be 100 different dishes.
- **The most neglected variable is time when it comes to managing State.** We can only think about this in abstract ways.
- "We (developer) do most of the State management in our heads."
    - There's no concrete way to communicate our understanding of States. This is one of the reasons why we have State Machines.

## What are the Essential Questions when people work with State Management?

- First, identify all the pieces of State that you're dealing with.
    - How is this information organized?
    - How can this data change over time?
    - How can you model this data?

## What's a Finite State Machines?

- "XState is like Redux with Rules"
- A finite state machine is a mathematical model of computation that describes the behavior of a system that can be in only one state at any given time.
- Finite State, you can only be in one State at a time.
    - It's more of a mode, "I'm awake & I'm asleep."
- It also describes how one can move from one State to another.

## What's the difference between a State Machine and Statecharts?

- Finite State Machines can represent everything.
- Statecharts are a formalism for modeling stateful, reactive systems.
- David Harel presented this formalism as an extension to state machines in his 1987 paper [Statecharts: A Visual Formalism for Complex Systems](http://www.inf.ed.ac.uk/teaching/courses/seoc/2005_2006/resources/statecharts.pdf).
    - A way to organize your states. "Sub-States."
- **More resources:**
    - **[Finite-state machine](https://en.wikipedia.org/wiki/Finite-state_machine)** article on Wikipedia
    - **[Understanding State Machines](https://www.freecodecamp.org/news/state-machines-basics-of-computer-science-d42855debc66/)** by Mark Shead
    - **[▶️ A-Level Comp Sci: Finite State Machin](https://www.youtube.com/watch?v=4rNYAvsSkwk)**

## How are State Machine addressing the big ideas of State management?

- Event-Action approach doesn't always make sense. A State Machine has a specific way of transitioning.
    - A state transition defines what the next state is, given the current state and event. State transitions are defined on state nodes.
- **Communication** with humans and machines.
- **More resources:**
    - **[Statecharts: A Visual Formalism for Complex Systems](http://www.inf.ed.ac.uk/teaching/courses/seoc/2005_2006/resources/statecharts.pdf)** by David Harel
    - **[The World of Statecharts](https://statecharts.github.io/)** by Erik Mogensen
    - [Constructing the User Interface with Statecharts](https://www.amazon.com/Constructing-User-Interface-Statecharts-Horrocks/dp/0201342782) by Ian Horrocks
- **Combinatorial Explosion**
    - State Machines is not something new; it has been implemented across different industries.

## The Overlap of music and State Machines and Statecharts

- When you look at music, there are infinite ways to express a melody; inherently, there are rules.
- **Music makes you a better visual thinker.**
    - This is an example when it comes to modeling State solutions.
- Music is centuries old; its theory is old. Computer science is the music theory of programming.
    - Music theory answers why "this" works, much like when you start using a library, and you realized that it's an elegant solution to a specific problem.

## Building a Statecharts for JavaScript

- The inspiration came from David's first job working with repetitive workflows. Wanting to solve this problem led to researching State Machines.
- Early days it was called "Estado," the Spanish word for State.

## Demo of XState

[Code sandbox demo](https://codesandbox.io/s/exciting-tereshkova-cjpdf?from-embed)

- Normal React Development:

```html
    <div className="App">
      <h1>{toggled ? "Toggled" : "Nope"}</h1>
      <h2>
        {state.value} ({state.context.count})
      </h2>
      <button
        onClick={() => {
          send("TOGGLE");
        }}
      >
        Toggle
      </button>
    </div>
...
```

- The problem is the all the business logic is inside the event handle.
- If you have more business requirements, you'll need to add 'defense logic' to handle more use cases.

## Adding XState

```js
import { createMachine, assign } from "xstate";
import { useMachine } from "@xstate/react";

const toggleMachine = createMachine({
  initial: "untoggled",
  context: {
    count: 0
  },
  states: {
    untoggled: {
      on: { TOGGLE: "toggled" }
    },
    toggled: {
      entry: assign({
        count: context => context.count + 1
      }),
      on: {
        TOGGLE: "untoggled"
      },
      after: {
        1000: "untoggled"
      }
    }
  }
});
```

- `useMachine(machine, options?)` - a React hook that interprets the given machine and starts a service that runs for the component's lifetime.

```js
const [state, send] = useMachine(toggleMachine, { devTools: true });
console.log(state);
const [toggled, setToggled] = useState(false);
```

- We are creating an event-driven approach to handling toggles.
- All the logic is handle inside `toggleMachine`
- With State Machines everything is an event (time is an event).
- Existing machines can be configured by passing the machine options as the 2nd argument of `useMachine(machine, options).`

```jsx
context: {
    count: 0
  },
```

- We can add a side-effects `count: context => context.count + 1` without affecting our main State.

## XState Visualizer

![](https://res.cloudinary.com/dg3gyk0gu/image/upload/v1618256533/transcript-images/state-management-2021-descriptions/xstate-visualizer.png)

## What's the workflow for design States?

- Pen and paper work pretty well. Modeling the behavior of a user is complicated.

![](https://res.cloudinary.com/dg3gyk0gu/image/upload/v1618256586/transcript-images/state-management-2021-descriptions/workflow-for-design-states.png)

- **Dev Tools for XState (coming soon)**
    - CodeSandbox also works pretty well for prototyping state.

## When is XState not appropriate?

- You don't need a library to implement State Machines. You can use patterns in each language.
- XState becomes more valuable when representing Statecharts.
- XState version 5 will be smaller. It will be explicit, small, and fast.
- [See Twitter](https://twitter.com/DavidKPiano/status/1226182960111591426?s=20)

XState for State Management in React Apps with David Khourshid

Clojure is a dynamic, general-purpose programming language, combining the approachability and interactive development of a scripting language with an efficient and robust infrastructure for multithreaded programming. Clojure is a compiled language, yet remains completely dynamic – every feature supported by Clojure is supported at runtime. Clojure provides easy access to the Java frameworks, with optional type hints and type inference, to ensure that calls to Java can avoid reflection.

clojure

Para iniciar con Clojure es necesario realizar algunas configuraciones e instalar algunas herramientas.
Lo primero es instalar [leiningen](https://leiningen.org) y configurar tu editor de código.
En este caso configuraremos VIM. Para esto instalaremos algunos ]plugins 

* [vim-fireplace](https://github.com/tpope/vim-fireplace)
* [vim-salve](https://github.com/tpope/vim-salve)
* [coc-conjure](https://github.com/jlesquembre/coc-conjure)

Configurar ambiente de desarrollo y VIM para Clojure

JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

In this video, we start by going to Begin.com and creating a new Deno app. We then clone the repo, inspect the code, and modify the response from HTML to JSON data. Next, we deploy the updates in an automated CI / CD process by merging the updates to our master GitHub branch.

Up and Running with Deno

The main purpose of a web server is to export an api. The most common protocol is http requsts. In this lesson, we will learn how to benchmark your app's http api's using autocannon in order to be able to track down performance bottlenecks or inefficient code.

Benchmark http requests using autocannonjs

To make our opengraph image generation function, we'll have to work out a way to pass the querystring variables from the original URL through to the React script running inside the headless browser. We choose to set them on the window using another injected script, and we also cover handling URL decoding of querystring components.

Passing variables to serverless functions using query strings

In this lesson, we'll learn how to set the httpOnly flag on our session id cookie to ensure it is inaccessible from javascript, thereby defeating theft of the session id from the XSS attack we crafted in the previous lesson. However, we'll still leave ourselves open to other dangers from XSS, which we'll exploit in our next lesson!

Set the httpOnly Cookie Flag in Express to Ensure Cookies are Inaccessible from JavaScript

In this lesson, we'll learn how to add https (and remove http) support to the localhost version of our express application. By adding https support, we'll be able to prevent a MITM (in this case Charles Proxy) from reading our session id, mitigating the attack known as "session hijacking".

Add https to a Localhost Express App to Prevent MITM Attacks

In this lesson, we'll learn what the SameSite cookie flag is, what it’s various settings are, and how it can be used to prevent most forms of CSRF vulnerabilities. We'll then demonstrate how it protects against the exploit we crafted in the previous lesson.

Mitigate CSRF Attacks by Setting the SameSite Cookie Flag in Express

In this lesson, we'll learn what CSRF tokens are, and how they are used to defeat Cross Site Request Forgery vulnerabilities. Even though we've defeated CSRF through the use of SameSite cookies, adding CSRF tokens are an important "defense in depth" strategy to ensure that browsers that don't support SameSite cookies can still be protected against CSRF.

Add CSRF Token Middleware to an Express Server to Mitigate CSRF

Gemini 2.0 has a context window of a million tokens, and this means that you can upload hundreds of files and allow it to inspect and analyze massive refactors across entire code bases. 

This lesson demonstrates concatenating an entire code base into a single file and then uploading it to AI Studio. Once within AI Studio, we ask it to find the types of tasks that it can evaluate for us. Then we select one of the tasks and ask it to generate instructions for that task. Once those instructions are complete, we then turn them over to Windsurf's Cascade agent, and we allow Windsurf's Cascade to do all of the work for us as we sit back, relax, and let the AI do our jobs.

Use Gemini 2.0 to Create Agent Instructions to Refactor an Entire Codebase

Learn how to display custom components in a [Tanstack Table cell](https://tanstack.com/table/latest/docs/guide/cells), including how to render capitalized text, apply conditional styling with class helper functions, and format dates using the `Intl` API for readable display. 

`flexRender` allows you to utilize the `cell` callback method in your column definitions. Tanstack table will call this function to render the custom component you defined.

Render Custom JSX in a Tanstack Table cell

Use tanstack table flexRender method to render custom components in a table component. Capitalize letters, apply conditional styling, and render dates with Intl

I'm extremely excited for the potential of AI watching your screen while you work. I decided to take Google's AI Studio for a spin, which just introduced a feature called "Stream Realtime", which allows AI Studio to observe your screen and listen to your microphone while you work.

This video is my initial attempt to try and coach AI Studio through the process of building a site from a reference site, essentially trying to build egghead.io from a Next.js starter template. And we'll explore the various attempts we make and what works and what doesn't.

Let AI Watch Your Screen: Build Next.js Pages with AIStudio's Stream Realtime


[Shadcn](https://ui.shadcn.com/docs) is a popular component library that allows you to install components into your codebase.

Learn how to install the [Table component](https://ui.shadcn.com/docs/components/table) and use that presentational component with [Tanstack table](https://tanstack.com/table/latest).


Display Tabular Data in React with Tanstack Table

Build a dynamic table component in React using shadcn component library and tanstack react table.

TypeScript's satisfies operator finally clicked for me when I realized it's almost always used for specific implementations of configuration objects. So this lesson walks you through the naive approaches I've taken before and how to solve them using the satisfies operator. After this, satisfies will be another tool in your belt in TypeScript. To clean up all the TypeScript code you have around configuration.

TypeScript's "satisfies" for Configuration

Windsurf and Cursor are both able to take an image and then use an agent to build out what it sees in that image. This lesson is going to compare Windsurf and Cursor by uploading the same image to both and giving them the same prompt. Comparing not only the results, but also the steps that they take to get there. We'll also try uploading additional images throughout the process to see what they do as far as revising along the way and improving the site as they go along. 

Windsurf Cascade vs. Cursor Composer Agent: Build a Site from an Image

In this lesson, you'll discover how to style View Transitions using CSS pseudo-selectors to create custom animation effects. We'll transform the default cross-fade into a smooth slide transition by targeting the ::view-transition-old and ::view-transition-new pseudo-elements. You'll learn how these powerful selectors give you precise control over your transition animations, allowing you to create more engaging and personalized user experiences with just a few lines of CSS.

Customize View Transitions with CSS Using view-transition-old and view-transition-new

In this lesson, you'll learn how to implement smooth state transitions in your web applications using the browser's built-in View Transitions API. We'll create a simple example that demonstrates how to animate between different text states with just a few lines of code - no external libraries required. This powerful native API makes it easy to add professional-looking transitions to your user interface, enhancing the user experience with minimal effort.

Create Smooth UI Transitions with the Native View Transitions API

I've been using Cursor for a very long time and their "Agent" feature in Composer is fairly new, so I'm still getting used to it. But since Windsurf recently got onto the stage with their Cascade agent, they've slowly been gaining the mind share on the UX for coding agents. I decided to put them to the test by putting Windsurf and Cursor on the exact same screen side by side trying to accomplish the same task and to see which workflow I would prefer. I've been a diehard Cursor user for over a year now, so it's going to take a lot for me to switch to a different IDE. But I just have to say, even from this simple demo, Windsurf is looking pretty nice.

This lesson is just going to walk through creating a CLI using both tools to print out inspirational quotes and to explore how they approach the step-by-step of installing packages and running commands and setting up all the files we need to get this running.

Windsurf Cascade vs. Cursor Composer Agent Side-by-Side Comparison

I've been using Cursor as my primary editor for over a year now, but recently I've heard wonderful things about Windsurf AI Agent features. I decided to record myself building out something I've always wanted to make, but never made the time for.

In this lesson, I demonstrate how to leverage Windsurf's powerful agent process to create a fun word-guessing game inspired by Heads Up. Watch as I build an interactive application featuring category selection and word navigation, complete with data hosting on GitHub Gists and deployment to GitHub Pages - all in under 30 minutes (before editing the lesson down to 12 minutes)!

What makes this project particularly exciting is how Windsurf eliminates the typical friction points of development. While this game was always on my project wishlist, the overhead of setup, configuration, and deployment made it hard to justify the time investment. Windsurf's agent process handles all these pain points seamlessly, from managing URLs to orchestrating deployment.

This lesson perfectly showcases how AI agents can help developers bring their backlog of project ideas to life, transforming what would typically be time-consuming tasks into efficient, enjoyable development experiences.

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