Implement syntax highlighting for syntax fragments

A new key 'highlighters' has been added to the toaster.conf file. The
value should be a line defining the languages to use that syntax for,
like [py/python]. The lines following are the template definitions, as
per the highlighter library.

1 files changed, 18 insertions, 1 deletions

diff --git a/src/generate_html.rs b/src/generate_html.rs
index 0de42a5..5abddf2 100644
--- a/src/generate_html.rs
+++ b/src/generate_html.rs
@@ -236,7 +236,24 @@ pub fn document_to_html(document: &MarkdownDocument, page: &Page, website: &Webs
                             warn!("Gallery-nav on page {from:?} has line without a '::' separator");
                         }
                     }),
-                    _ => wrap!("pre", format!("class='{language}'"), html!("{}", sanitize_text(content, false))),
+                    _ => wrap!("pre", format!("class='{language}'"), {
+                        if let Some(i) = website.highlighters.languages.get(language) {
+                            let mut source = String::new();
+                            let highlighter = &website.highlighters.highlighters[*i];
+                            for span in highlighter.highlight(content) {
+                                if span.tag.is_empty() {
+                                    source.push_str(&sanitize_text(&span.text, false));
+                                } else {
+                                    source.push_str(&format!("<span class='{}'>", span.tag.to_lowercase()));
+                                    source.push_str(&sanitize_text(&span.text, false));
+                                    source.push_str("</span>");
+                                }
+                            }
+                            html!("{source}");
+                        } else {
+                            html!("{}", sanitize_text(content, false))
+                        }
+                    })
                 }
             }
             Block::Break => html!("<hr>"),