Page meta from frontmatter

crates/service/service-webpage/src/components/md.rs

@@ -1,33 +1,51 @@
+use lazy_static::lazy_static;
+use markdown_it::parser::block::{BlockRule, BlockState};
+use markdown_it::parser::core::Root;
 use markdown_it::parser::inline::{InlineRule, InlineState};
-use markdown_it::{Node, NodeValue, Renderer};
+use markdown_it::{MarkdownIt, Node, NodeValue, Renderer};
 use maud::{Markup, PreEscaped, Render};
 use std::str::FromStr;
 
 use crate::components::fa::FAIcon;
 use crate::components::mangle::{MangledBetaEmail, MangledGoogleEmail};
 
+lazy_static! {
+	static ref MdParser: MarkdownIt = {
+		let mut md = markdown_it::MarkdownIt::new();
+		markdown_it::plugins::cmark::add(&mut md);
+		markdown_it::plugins::html::add(&mut md);
+		md.inline.add_rule::<InlineEmote>();
+		md.inline.add_rule::<InlineEmote>();
+		md.inline.add_rule::<InlineMdx>();
+		md.block.add_rule::<FrontMatter>().before_all();
+		md
+	};
+}
+
 pub struct Markdown<'a>(pub &'a str);
 
 impl Render for Markdown<'_> {
 	fn render(&self) -> Markup {
-		// TODO: init once
-		let md = &mut markdown_it::MarkdownIt::new();
-		markdown_it::plugins::cmark::add(md);
-		markdown_it::plugins::html::add(md);
-		md.inline.add_rule::<InlineEmote>();
-		md.inline.add_rule::<InlineMdx>();
-
-		let md = md.parse(self.0);
+		let md = Self::parse(self.0);
 		let html = md.render();
-
 		return PreEscaped(html);
 	}
 }
 
+impl Markdown<'_> {
+	pub fn parse(md_str: &str) -> Node {
+		MdParser.parse(md_str)
+	}
+}
+
 //
 // MARK: extensions
 //
 
+//
+// MARK: emote
+//
+
 #[derive(Debug)]
 pub struct InlineEmote(String);
 
@@ -66,6 +84,10 @@ impl InlineRule for InlineEmote {
 	}
 }
 
+//
+// MARK: mdx
+//
+
 #[derive(Debug)]
 pub struct InlineMdx(String);
 
@@ -245,3 +267,58 @@ fn mdx_include(mdx: &str, _node: &Node, fmt: &mut dyn Renderer) -> bool {
 
 	return true;
 }
+
+//
+// MARK: frontmatter
+//
+
+#[derive(Debug)]
+/// AST node for front-matter
+pub struct FrontMatter {
+	pub content: String,
+}
+
+impl NodeValue for FrontMatter {
+	fn render(&self, _node: &Node, _fmt: &mut dyn Renderer) {}
+}
+
+impl BlockRule for FrontMatter {
+	fn run(state: &mut BlockState<'_, '_>) -> Option<(Node, usize)> {
+		// check the parent is the document Root
+		if !state.node.is::<Root>() {
+			return None;
+		}
+
+		// check we are on the first line of the document
+		if state.line != 0 {
+			return None;
+		}
+
+		// check line starts with opening dashes
+		let opening = state
+			.get_line(state.line)
+			.chars()
+			.take_while(|c| *c == '-')
+			.collect::<String>();
+		if !opening.starts_with("---") {
+			return None;
+		}
+
+		// Search for the end of the block
+		let mut next_line = state.line;
+		loop {
+			next_line += 1;
+			if next_line >= state.line_max {
+				return None;
+			}
+
+			let line = state.get_line(next_line);
+			if line.starts_with(&opening) {
+				break;
+			}
+		}
+
+		let (content, _) = state.get_lines(state.line + 1, next_line, 0, true);
+		Some((Node::new(FrontMatter { content }), next_line + 1))
+	}
+}