mdbook_callouts/
lib.rs

1use mdbook_driver::book::{Book, BookItem, Chapter};
2use mdbook_driver::errors::Error;
3use mdbook_preprocessor::PreprocessorContext;
4use once_cell::sync::Lazy;
5use regex::Regex;
6use rust_embed::Embed;
7
8#[derive(Embed)]
9#[folder = "assets/"]
10struct Asset;
11
12pub struct Preprocessor;
13
14impl mdbook_preprocessor::Preprocessor for Preprocessor {
15    fn name(&self) -> &str {
16        "callouts"
17    }
18
19    fn supports_renderer(&self, renderer: &str) -> Result<bool, Error> {
20        Ok(renderer == "html")
21    }
22
23    fn run(&self, _ctx: &PreprocessorContext, mut book: Book) -> Result<Book, Error> {
24        let mut error: Option<Error> = None;
25        book.for_each_mut(|item: &mut BookItem| {
26            if error.is_some() {
27                return;
28            }
29            if let BookItem::Chapter(ref mut chapter) = *item {
30                if let Err(err) = handle_chapter(chapter) {
31                    error = Some(err)
32                }
33            }
34        });
35        error.map_or(Ok(book), Err)
36    }
37}
38
39fn handle_chapter(chapter: &mut Chapter) -> Result<(), Error> {
40    chapter.content = inject_stylesheet(&chapter.content)?;
41    chapter.content = render_callouts(&chapter.content)?;
42    Ok(())
43}
44
45fn inject_stylesheet(content: &str) -> Result<String, Error> {
46    let style = Asset::get("style.css").expect("style.css not found in assets");
47    let style = std::str::from_utf8(style.data.as_ref())?;
48    Ok(format!("<style>\n{style}\n</style>\n{content}"))
49}
50
51fn render_callouts(content: &str) -> Result<String, Error> {
52    static RE: Lazy<Regex> = Lazy::new(|| {
53        // Regex::new(r"(?m)^> \[!(?P<kind>[^\]]+)\]\s*$(?P<body>(?:\n>.*)*)")
54        Regex::new(r"(?m)^> \[!(?P<kind>[^\]]+)\](?P<title>\ {1}[^\n]+)?$(?P<body>(?:\n>.*)*)")
55            .expect("failed to parse regex")
56    });
57    let alerts = Asset::get("alerts.tmpl").expect("alerts.tmpl not found in assets");
58    let alerts = std::str::from_utf8(alerts.data.as_ref())?;
59    let content = RE.replace_all(content, |caps: &regex::Captures| {
60        let kind = caps
61            .name("kind")
62            .expect("kind not found in regex")
63            .as_str()
64            .trim()
65            .to_lowercase();
66        let title = caps
67            .name("title")
68            .map(|m| m.as_str().trim())
69            .unwrap_or(kind.as_str())
70            .to_lowercase();
71        let body = caps
72            .name("body")
73            .expect("body not found in regex")
74            .as_str()
75            .replace("\n>\n", "\n\n")
76            .replace("\n> ", "\n");
77
78        alerts
79            .replace("{title}", &title)
80            .replace("{kind}", &kind)
81            .replace("{body}", &body)
82    });
83    Ok(content.into())
84}
mdbook_callouts/lib.rs

mdbook_callouts/
lib.rs
