content: building-an-ssg-in-rust

content/index.md

@@ -1,3 +1,7 @@
+---
+title: Home
+---
+
 # Welcome to my website! :heart:
 
 You have found this little floating rock in the middle of the Internet! Congrats 🎉
@@ -15,6 +19,7 @@ Throughout the last few years I've been taking photos of random things in random
 [Take me to the map!](/map/)
 
 ## A short guide to the Hanafuda card game
+
 I've been playing Hanafuda for a while now, so I decided to write a short introduction into this interesting card game. I am by no means good at the game, so take everything with a grain of salt, but I feel like it should be enough to get you started.
 
 [Take me to the guide!](/posts/hanafuda/)

content/posts/building-an-ssg-in-rust/bibliography.bib

@@ -0,0 +1,17 @@
+@article{10.1145/3236774,
+    author      = {Mokhov, Andrey and Mitchell, Neil and Peyton Jones, Simon},
+    title       = {Build systems \`{a} la carte},
+    year        = {2018},
+    issue_date  = {September 2018},
+    publisher   = {Association for Computing Machinery},
+    address     = {New York, NY, USA},
+    volume      = {2},
+    number      = {ICFP},
+    url         = {https://doi.org/10.1145/3236774},
+    doi         = {10.1145/3236774},
+    journal     = {Proc. ACM Program. Lang.},
+    month       = jul,
+    articleno   = {79},
+    numpages    = {29},
+    keywords    = {algorithms, build systems, functional programming}
+}

content/posts/building-an-ssg-in-rust/index.md

@@ -0,0 +1,179 @@
+---
+title: Building an SSG in Rust
+date: 2024-10-05T12:29:54.111Z
+desc: >
+  Some reflections on using Rust to write a static site generator...
+---
+
+For the past few months in my spare time, I’ve been programming a simple
+library in Rust that can be used to generate a static website from markdown
+files and images. I myself use it to generate this very website, and it is
+available under the GPL license on
+[crates.io](https://crates.io/crates/hauchiwa), though it might be outdated -
+the latest version is always on [GitHub](https://github.com/kamoshi/hauchiwa)
+and the documentation is available on
+[docs.rs](https://docs.rs/hauchiwa/latest/hauchiwa/).
+
+You can add it to your own project in two ways, like so:
+
+```rust
+hauchiwa = "*"
+hauchiwa = { git = "https://github.com/kamoshi/hauchiwa" }
+```
+
+## Background
+
+Throughout the years I've tried many different tools, some of them better than
+others.  For example, I really liked the speed of Hugo and the flexibility of
+Astro, but none of the available tools fulfilled my needs. I wanted both speed
+and lots of flexibility at the same time, I figured that I needed to create my own
+generator from scratch to accomplish what I want to do.
+
+The first thing I had to do was choose the language and the ecosystem for the
+generator, and as you already know, I ended up with Rust. I've considered
+different languages and ecosystems - like Haskell - but Rust currently has a lot
+of industrial momentum, that's the current zeitgeist.
+
+Contrary to what many people say, Rust is not a silver bullet, the fact that in
+Rust you have to deal with memory, even if it's automatic most of the time can
+be a deal breaker. Sometimes you just don't need to care about memory, so having
+To deal with it is a waste of mental energy. Nevertheless, I decided that this
+tradeoff is worth taking in this case, given that Rust has:
+
+- lots of good enough libraries
+- vibrant community
+- ergonomic abstractions
+- automatic memory management with borrow checker
+
+So given these facts, I came to the conclusion that going with Rust will make it
+easy to find any library I need to create a generator, and the memory management
+is an acceptable tradeoff for the fact that Rust programs are generally quite
+fast and compile to a single binary.
+
+When it comes to the actual form factor of the library, I wanted it to be really
+minimal and allow for maximal flexibility. I really enjoyed the way Astro works,
+you use it as a general framework, you have lots of freedom to define each page
+on the generated website. I would like to preserve this spirit in my library,
+while at the same time creating a robust and idiomatic API in Rust.
+
+Some of the requirements I had in mind are:
+
+- The library should be decoupled from any templating engine, the user should
+  be able to choose their own way to generate the HTML, they should even be able
+  to do it by concatenating strings manually if they so desire.
+- The user shouldn't be limited to Markdown, the library should be format
+  agnostic and the user should be allowed to bring any parser they want and use
+  it to convert any kind of file to HTML.
+- The user should be able to generate HTML pages that don't have any original
+  source files related to them, think of dynamically generated lists of pages,
+  tags, etc.
+- There should be a way to render different pages differently, some collections
+  of Markdown files should output different looking pages.
+- The library should make it easy to watch for changes and allow the user to add
+  live reload while editing their website.
+
+In my library I've tried to address all of these requirements, but it's still
+being worked out. I've spent a lot of time thinking through lots of design
+decisions until I landed on some sweet spot in the design space, but even now,
+I'm not sure if there are better ways to accomplish some things...
+
+## Incremental build system
+
+To implement the incremental build process and live reload, I've ended up reading
+an article called _Build systems à la carte_, which goes over different ways to
+implent a build system in Haskell, I would recommend reading it; it was really
+useful. Based on some prior experience as well as this article, I've decided to
+go with a _suspending_ scheduler, as well as both _verifying traces_ and
+_constructive traces_ for the rebuilding strategy.
+
+_Suspending_ means that the moment a certain page requires, for example, a PNG
+image or a CSS stylesheet I pause the page build process in order to prepare the
+required asset. In practice, this just means I call a function that is supposed
+to build that image, so it's not anything difficult.
+
+```rust
+  /// Get compiled CSS style by file path.
+	pub fn get_styles(&self, path: &Utf8Path) -> Option<Utf8PathBuf> {
+		let input = self.items.values().find(|item| item.file == path)?;
+		if !matches!(input.data, Input::Stylesheet(..)) {
+			return None;
+		}
+
+		self.tracked
+			.borrow_mut()
+			.insert(input.file.clone(), input.hash.clone());
+
+		self.schedule(input)
+	}
+```
+
+This function calls another function `schedule`, which builds the asset if it
+needs to be built.
+
+```rust
+  fn schedule(&self, input: &InputItem) -> Option<Utf8PathBuf> {
+		let res = self.builder.read().unwrap().check(input);
+		if res.is_some() {
+			return res;
+		}
+
+		let res = self.builder.write().unwrap().build(input);
+		Some(res)
+	}
+```
+
+Here `self.builder` is behind an `RwLock` which needs to be acquired in order to
+build the asset. This is just an implementation detail; `RwLock` allows the
+builder to be shared in a multithreaded environment and allows many reads at
+the same time. This is optimal for the case when the asset is in fact already
+built.
+
+When it comes to the traces, I've decided to use the following strategy to trace
+input assets:
+
+```rust
+#[derive(Debug)]
+pub(crate) struct InputItem {
+	pub(crate) hash: Vec<u8>,
+	pub(crate) file: Utf8PathBuf,
+	pub(crate) slug: Utf8PathBuf,
+	pub(crate) data: Input,
+}
+```
+
+Each asset has a binary `hash` and with this information alone we can easily
+check if the input asset has changed in a meaningful way between two builds.
+
+In order to trace the individual build tasks that are defined by the user to
+generate the HTML pages, I've decided to use the following struct:
+
+```rust
+#[derive(Debug)]
+struct Trace<G: Send + Sync> {
+	task: Task<G>,
+	init: bool,
+	deps: HashMap<Utf8PathBuf, Vec<u8>>,
+}
+```
+
+Here we have `task` which is in fact a closure pointer - a pointer to a function
+defined by the user of the library. This function consumes a `Sack` which is the access point ftracks
+the dependencies required by the task.
+
+```rust
+/// Task function pointer used to dynamically generate a website page.
+type TaskFnPtr<G> = Arc<dyn Fn(Sack<G>) -> Vec<(Utf8PathBuf, String)> + Send + Sync>;
+
+/// Wraps `TaskFnPtr` and implements `Debug` trait for function pointer.
+pub(crate) struct Task<G: Send + Sync>(TaskFnPtr<G>);
+```
+
+These dependencies are then kept as the `deps` field, so we can check if any of
+the input files required by a certain task have changed. If they have, we can
+rebuild the task and update the dependencies. There's also the `init` field
+which just forces the task to be built for the first time.
+
+This is just the bare minimum to make this build system work, there are still
+some open questions, like "What if the build task is nondeterministic, should it
+be rebuilt every time?". Please take a look at the library code to see how the
+current build system works in detail.

content/posts/typeclasses/index.md

@@ -103,7 +103,6 @@ add d a b = (+) d a b
 Effectively, `Num a` serves as a table of operations for the `Num` class for type `a`.
 This elegant mechanism allows Haskell to implement polymorphism with type classes while maintaining strict type safety.
 
-
 ## Kinds
 
 A type in Haskell is a classification that defines what kind of data a value can represent.
@@ -116,11 +115,13 @@ The notation for kinds in Haskell uses an asterisk `*` to represent the most bas
 You can check the kind of any type by using the `:kind` command in GHCi.
 
 The kind of `Int` is `*`, indicating that `Int` is a concrete type.
+
 ```haskell
 Int :: *
 ```
 
 Similarly, the kind of `Float` is `*`, signifying that it is also a concrete type.
+
 ```haskell
 Float :: *
 ```
@@ -130,14 +131,17 @@ For instance, type classes introduce a kind called `Constraint`, denoted as `=>`
 The kind Constraint is used to represent constraints on types and is commonly encountered when defining type classes and their instances.
 
 The kind of `Num` is `* -> Constraint`, showing that `Num` is a type class that takes a type (like `Int`) as an argument.
+
 ```haskell
 Num :: * -> Constraint
 ```
 
 When `Num` is applied to `Int`, it becomes a constraint on the `Int` type, indicating that `Int` is an instance of the `Num` type class.
+
 ```haskell
 Num Int :: Constraint
 ```
+
 Another example of a kind in Haskell is the kind of unary type constructors `* -> *`.
 These unary type constructors are similar to generic types in other languages because they accept a type parameter and produce a new type.
 The signature `* -> *` signifies that the type constructor transforms one concrete type into another concrete type.
@@ -179,7 +183,6 @@ In this definition, `Either` is a binary type constructor because it requires tw
 The `Either` type is often used for scenarios where a value can have one of two possible types, such as representing success or failure or providing an alternative to error handling.
 Conventionally, the `Left` value indicates error conditions, while the `Right` value signifies valid or correct values.
 
-
 ### Higher Kinded Types
 
 In Haskell, understanding the concept of "Higher Kinded Types" is crucial for grasping how certain more abstract type classes work.
@@ -231,7 +234,6 @@ instance Functor (Either a) where
 In the instance declaration above, we specify that, for any type `a`, `Either a` is an instance of the `Functor` type class.
 This allows you to use the `fmap` function with `Either a`, providing a way to map over the second type argument of the `Either` type while keeping the first type argument fixed.
 
-
 ## Other languages
 
 ### Scala

src/main.rs

@@ -10,7 +10,7 @@ use chrono::{DateTime, Datelike, Utc};
 use clap::{Parser, ValueEnum};
 use hauchiwa::{Collection, Sack, Website};
 use hypertext::Renderable;
-use model::{Post, Slideshow, Wiki};
+use model::{Home, Post, Slideshow, Wiki};
 
 #[derive(Parser, Debug, Clone)]
 struct Args {
@@ -73,6 +73,7 @@ fn main() {
 
 	let website = Website::setup()
 		.add_collections(vec![
+			Collection::glob_with::<Home>("content", "index.md", ["md"].into()),
 			Collection::glob_with::<Post>("content", "about.md", ["md"].into()),
 			Collection::glob_with::<Post>("content", "posts/**/*", ["md", "mdx"].into()),
 			Collection::glob_with::<Slideshow>("content", "slides/**/*", ["md", "lhs"].into()),
@@ -87,6 +88,13 @@ fn main() {
 			("editor", "./js/flox/main.ts"),
 			("lambda", "./js/flox/lambda.ts"),
 		])
+		// Task: generate home page
+		.add_task(|sack| {
+			let query = sack.get_content::<Home>("").unwrap();
+			let (parsed, _, _) = text::md::parse(query.content, &sack, query.area, None);
+			let out_buff = html::home(&sack, &parsed);
+			vec![("index.html".into(), out_buff)]
+		})
 		.add_task(|sack| {
 			let query = sack.get_content::<Post>("about").unwrap();
 			let (parsed, outline, bib) =
@@ -147,12 +155,6 @@ fn main() {
 		})
 		// Task: generate search
 		.add_task(|sack| vec![("search/index.html".into(), crate::html::search(&sack))])
-		// Task: generate home page
-		.add_task(|sack| {
-			let data = std::fs::read_to_string("content/index.md").unwrap();
-			let (parsed, _, _) = text::md::parse(&data, &sack, "".into(), None);
-			vec![("index.html".into(), crate::html::home(&sack, &parsed))]
-		})
 		.add_task(|sack| {
 			let query = sack.get_content("projects/flox").unwrap();
 

src/model.rs

@@ -1,6 +1,12 @@
 use chrono::{DateTime, Utc};
 use serde::Deserialize;
 
+/// Represents a wiki page
+#[derive(Deserialize, Debug, Clone)]
+pub struct Home {
+	pub title: String,
+}
+
 /// Represents a simple post.
 #[derive(Deserialize, Debug, Clone)]
 pub struct Post {

styles/styles.scss

@@ -1,30 +1,30 @@
 // Config
-@use 'root';
-@use 'reset';
-@use 'fonts';
-@use 'base';
-@use 'markdown';
-@use 'kanagawa';
+@use "root";
+@use "reset";
+@use "fonts";
+@use "base";
+@use "markdown";
+@use "kanagawa";
 
 // Components
-@use 'components/map';
-@use 'components/search';
-@use 'components/link-tree';
-@use 'components/bibliography';
-@use 'components/kanji';
+@use "components/map";
+@use "components/search";
+@use "components/link-tree";
+@use "components/bibliography";
+@use "components/kanji";
 
 // Partials
-@use 'partials/navbar';
-@use 'partials/footer';
+@use "partials/navbar";
+@use "partials/footer";
 
 // Shortcodes
-@use 'shortcodes/timeline';
-@use 'shortcodes/marginnote';
+@use "shortcodes/timeline";
+@use "shortcodes/marginnote";
 
 // Layouts
-@use 'layouts/home';
-@use 'layouts/page';
-@use 'layouts/list';
+@use "layouts/home";
+@use "layouts/page";
+@use "layouts/list";
 
 // Special
-@use 'flox';
+@use "flox";