markdown rendering refactor and addition of code syntax highlighting

currently syntax highlighting is limited to the default syntax
definitions that syntect comes pre-loaded with (which is the same
as sublime text's out-of-the-box language support)

src/commonmark.rs

@@ -0,0 +1,91 @@
+use pulldown_cmark::{CodeBlockKind, CowStr, Event, Parser, Tag};
+use syntect::html::{ClassStyle, ClassedHTMLGenerator};
+use syntect::parsing::SyntaxSet;
+use syntect::util::LinesWithEndings;
+
+#[derive(Debug, thiserror::Error)]
+pub enum CommonMarkError {
+	#[error("Syntax highlighting error")]
+	SyntectError(#[from] syntect::Error),
+}
+
+struct SyntectContext {
+	syntax_set: SyntaxSet,
+}
+
+pub struct CommonMarkRenderer {
+	syntect_context: SyntectContext,
+}
+
+impl CommonMarkRenderer {
+	pub fn new() -> Self {
+		let syntax_set = SyntaxSet::load_defaults_newlines();
+		CommonMarkRenderer { syntect_context: SyntectContext { syntax_set } }
+	}
+
+	fn highlight_code(&self, code: &str, language: &str) -> Result<String, CommonMarkError> {
+		let syntax = self
+			.syntect_context
+			.syntax_set
+			.find_syntax_by_extension(language)
+			.unwrap_or_else(|| self.syntect_context.syntax_set.find_syntax_plain_text());
+
+		let mut html_generator = ClassedHTMLGenerator::new_with_class_style(
+			syntax,
+			&self.syntect_context.syntax_set,
+			ClassStyle::SpacedPrefixed { prefix: "sh-" },
+		);
+		for line in LinesWithEndings::from(code) {
+			html_generator.parse_html_for_line_which_includes_newline(line)?;
+		}
+		Ok(format!("<pre><code>{}</code></pre>", html_generator.finalize()))
+	}
+
+	fn highlight_codeblocks<'input>(
+		&self,
+		events: Parser<'input, '_>,
+	) -> Result<impl Iterator<Item = Event<'input>> + 'input, CommonMarkError> {
+		let mut modified_events = Vec::new();
+		let mut code_buffer = String::new();
+		let mut is_in_code_block = false;
+
+		for event in events {
+			match event {
+				Event::Start(Tag::CodeBlock(_)) => {
+					is_in_code_block = true;
+					code_buffer.clear();
+				}
+				Event::End(Tag::CodeBlock(kind)) => {
+					if is_in_code_block {
+						let language = if let CodeBlockKind::Fenced(language) = kind {
+							language.to_string()
+						} else {
+							String::new()
+						};
+						let html = self.highlight_code(&code_buffer, &language)?;
+						modified_events.push(Event::Html(CowStr::Boxed(html.into())));
+						is_in_code_block = false;
+					}
+				}
+				Event::Text(text) => {
+					if is_in_code_block {
+						code_buffer.push_str(&text);
+					} else {
+						modified_events.push(Event::Text(text))
+					}
+				}
+				event => modified_events.push(event),
+			}
+		}
+
+		Ok(modified_events.into_iter())
+	}
+
+	pub fn render_to_html(&self, s: &str) -> Result<String, CommonMarkError> {
+		let parser = Parser::new_ext(s, pulldown_cmark::Options::all());
+		let events = self.highlight_codeblocks(parser)?;
+		let mut output = String::new();
+		pulldown_cmark::html::push_html(&mut output, events);
+		Ok(output)
+	}
+}

src/main.rs

@@ -5,6 +5,7 @@ use anyhow::Context;
 use std::env;
 use std::path::{Path, PathBuf};
 
+mod commonmark;
 mod config;
 mod site;
 mod util;

src/site.rs

@@ -7,7 +7,7 @@ use actix_web::{Either, HttpRequest, HttpResponse};
 use chrono::{Datelike, TimeZone};
 use itertools::Itertools;
 
-use crate::{config, util};
+use crate::{commonmark, config, util};
 
 type UriPath = String;
 type Tag = String;
@@ -16,25 +16,35 @@ type Tag = String;
 pub enum ContentError {
 	#[error("Content rendering I/O error with path {0}")]
 	IOError(PathBuf, #[source] std::io::Error),
+
+	#[error("CommonMark rendering error with path {0}")]
+	CommonMarkError(PathBuf, #[source] commonmark::CommonMarkError),
 }
 
-fn render_content(path: &PathBuf) -> Result<String, ContentError> {
+pub struct ContentRenderer {
+	commonmark_renderer: commonmark::CommonMarkRenderer,
+}
+
+impl ContentRenderer {
+	pub fn new() -> Result<Self, ContentError> {
+		Ok(ContentRenderer { commonmark_renderer: commonmark::CommonMarkRenderer::new() })
+	}
+
+	pub fn render(&self, path: &PathBuf) -> Result<String, ContentError> {
 		let raw_content = match std::fs::read_to_string(path) {
 			Err(e) => return Err(ContentError::IOError(path.clone(), e)),
 			Ok(s) => s,
 		};
 		match path.extension().unwrap_or_default().to_str() {
-		Some("md") => {
+			Some("md") => match self.commonmark_renderer.render_to_html(&raw_content) {
-			let parser = pulldown_cmark::Parser::new_ext(&raw_content, pulldown_cmark::Options::all());
+				Err(e) => return Err(ContentError::CommonMarkError(path.clone(), e)),
-			let mut output = String::new();
+				Ok(output) => Ok(output),
-			// TODO: use write_html() instead because that can actually return errors instead of just panicking
+			},
-			pulldown_cmark::html::push_html(&mut output, parser);
-			Ok(output)
-		}
 			Some("html") | Some("htm") => Ok(raw_content),
 			_ => Ok(raw_content),
 		}
 	}
+}
 
 #[derive(Debug, thiserror::Error)]
 pub enum SiteError {
@@ -110,12 +120,10 @@ pub struct Post {
 	pub tags: Vec<Tag>,
 }
 
-impl TryFrom<config::Post> for Post {
+impl Post {
-	type Error = SiteError;
+	pub fn try_from(value: config::Post, content_renderer: &ContentRenderer) -> Result<Self, SiteError> {
-
-	fn try_from(value: config::Post) -> Result<Self, Self::Error> {
 		let url = format!("/{:04}/{:02}/{:02}/{}", value.date.year(), value.date.month(), value.date.day(), value.slug);
-		let content_html = render_content(&value.file_path)?;
+		let content_html = content_renderer.render(&value.file_path)?;
 		let tags = value.tags.map_or_else(|| Vec::new(), |x| x.clone());
 		Ok(Post {
 			url, //
@@ -134,11 +142,9 @@ pub struct Page {
 	pub content_html: String,
 }
 
-impl TryFrom<config::Page> for Page {
+impl Page {
-	type Error = SiteError;
+	pub fn try_from(value: config::Page, content_renderer: &ContentRenderer) -> Result<Self, SiteError> {
-
+		let content_html = content_renderer.render(&value.file_path)?;
-	fn try_from(value: config::Page) -> Result<Self, Self::Error> {
-		let content_html = render_content(&value.file_path)?;
 		Ok(Page {
 			url: value.url, //
 			title: value.title,
@@ -182,7 +188,11 @@ pub struct SiteContent {
 }
 
 impl SiteContent {
-	pub fn new(pages_config: config::Pages, posts_config: config::Posts) -> Result<Self, SiteError> {
+	pub fn new(
+		pages_config: config::Pages,
+		posts_config: config::Posts,
+		content_renderer: &ContentRenderer,
+	) -> Result<Self, SiteError> {
 		let mut alternate_url_mappings = AlternateUrlMappings::new();
 		let mut post_tag_mappings = PostsByTag::new();
 
@@ -190,7 +200,7 @@ impl SiteContent {
 		let mut pages = Vec::new();
 		let mut pages_by_url = HashMap::new();
 		for (index, page_config) in pages_config.pages.iter().enumerate() {
-			let page = Page::try_from(page_config.clone())?;
+			let page = Page::try_from(page_config.clone(), content_renderer)?;
 
 			if let Some(old_urls) = &page_config.alternate_urls {
 				alternate_url_mappings.add_mappings(old_urls, &page.url);
@@ -205,7 +215,7 @@ impl SiteContent {
 		let mut posts = Vec::new();
 		let mut posts_by_url = HashMap::new();
 		for (index, post_config) in posts_config.posts.iter().sorted_by(|a, b| b.date.cmp(&a.date)).enumerate() {
-			let post = Post::try_from(post_config.clone())?;
+			let post = Post::try_from(post_config.clone(), content_renderer)?;
 
 			if let Some(old_urls) = &post_config.alternate_urls {
 				alternate_url_mappings.add_mappings(old_urls, &post.url);
@@ -262,7 +272,8 @@ impl SiteContent {
 
 pub struct SiteService {
 	pub server_config: config::Server,
-	pub renderer: tera::Tera,
+	pub content_renderer: ContentRenderer,
+	pub template_renderer: tera::Tera,
 	pub content: RwLock<SiteContent>,
 }
 
@@ -272,7 +283,8 @@ impl SiteService {
 		pages_config: config::Pages,
 		posts_config: config::Posts,
 	) -> Result<Self, SiteError> {
-		let content = SiteContent::new(pages_config, posts_config)?;
+		let content_renderer = ContentRenderer::new()?;
+		let content = SiteContent::new(pages_config, posts_config, &content_renderer)?;
 		let mut templates_path = PathBuf::from(&server_config.templates_path);
 		templates_path.push("**/*");
 		log::debug!("Using templates path: {:?}", templates_path);
@@ -283,7 +295,8 @@ impl SiteService {
 		);
 		Ok(SiteService {
 			server_config, //
-			renderer,
+			content_renderer,
+			template_renderer: renderer,
 			content: RwLock::new(content),
 		})
 	}
@@ -295,7 +308,7 @@ impl SiteService {
 		if let Some(post) = post {
 			context.insert("post", post);
 		}
-		HttpResponse::Ok().body(self.renderer.render("post.html", &context).unwrap())
+		HttpResponse::Ok().body(self.template_renderer.render("post.html", &context).unwrap())
 	}
 
 	pub fn serve_posts_by_tag(&self, tag: &Tag) -> HttpResponse {
@@ -304,7 +317,7 @@ impl SiteService {
 		let mut context = tera::Context::new();
 		context.insert("tag", tag);
 		context.insert("posts", &posts);
-		HttpResponse::Ok().body(self.renderer.render("tag.html", &context).unwrap())
+		HttpResponse::Ok().body(self.template_renderer.render("tag.html", &context).unwrap())
 	}
 
 	pub fn serve_posts_archive(&self) -> HttpResponse {
@@ -312,7 +325,7 @@ impl SiteService {
 		let posts = content.get_posts_ordered_by_date();
 		let mut context = tera::Context::new();
 		context.insert("posts", &posts);
-		HttpResponse::Ok().body(self.renderer.render("archive.html", &context).unwrap())
+		HttpResponse::Ok().body(self.template_renderer.render("archive.html", &context).unwrap())
 	}
 
 	pub fn serve_rss_feed(&self) -> HttpResponse {
@@ -349,14 +362,14 @@ impl SiteService {
 				log::debug!("Found page content at {}", req.path());
 				let mut context = tera::Context::new();
 				context.insert("page", page);
-				let rendered = self.renderer.render("page.html", &context).unwrap();
+				let rendered = self.template_renderer.render("page.html", &context).unwrap();
 				Some(Either::Left(HttpResponse::Ok().body(rendered)))
 			}
 			Some(Content::Post(post)) => {
 				log::debug!("Found post content at {}", req.path());
 				let mut context = tera::Context::new();
 				context.insert("post", post);
-				let rendered = self.renderer.render("post.html", &context).unwrap();
+				let rendered = self.template_renderer.render("post.html", &context).unwrap();
 				Some(Either::Left(HttpResponse::Ok().body(rendered)))
 			}
 			Some(Content::Redirect(url)) => {