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.

2 files changed, 64 insertions, 2 deletions

diff --git a/src/collect_files.rs b/src/collect_files.rs
index 7a3c464..18d75f1 100644
--- a/src/collect_files.rs
+++ b/src/collect_files.rs
@@ -1,5 +1,6 @@
 use crate::*;
 
+use highlight::*;
 use vagabond::*;
 
 use std::collections::HashMap;
@@ -8,6 +9,7 @@ use std::collections::HashMap;
 pub struct Website {
     pub name: String,
     pub config: HashMap<String, String>,
+    pub highlighters: Highlighters,
     pub pages: Vec<Page>,
     pub redirects: Vec<Redirect>,
     pub static_files: Vec<StaticItem>,  // Redirects, !-prefixed-dir contents
@@ -60,6 +62,10 @@ pub trait LinkFrom {
     }
 }
 
+pub struct Highlighters {
+    pub languages: HashMap<String, usize>,
+    pub highlighters: Vec<Highlighter>,
+}
 
 impl Page {
     pub fn root(&self) -> String {
@@ -96,8 +102,13 @@ impl Website {
                 Err(err) => fatal!("Couldn't open {:?}: {:?}", &path, err),
             },
             config: HashMap::new(),
+            highlighters: Highlighters {
+                languages: HashMap::new(),
+                highlighters: Vec::new(),
+            },
         };
         new.collect_entry(path, path);
+        new.parse_highlighters();
         return new;
     }
 
@@ -149,7 +160,7 @@ impl Website {
             let mut key = None;
             let mut value = String::new();
             for line in config.lines() {
-                if line.starts_with(" ") {
+                if line.starts_with(" ") || line.trim().is_empty() {
                     value.push_str(line.trim());
                     value.push('\n');
                 } else {
@@ -268,6 +279,40 @@ impl Website {
         }
     }
 
+    pub fn parse_highlighters(&mut self) {
+        let mut languages = Vec::new();
+        let mut source = String::new();
+        for line in self.get_config("highlighters").lines() {
+            if let Some(line) = line.trim().strip_prefix('[') {
+                if let Some(line) = line.strip_suffix(']') {
+                    // Bank the current source.
+                    if !languages.is_empty() {
+                        let i = self.highlighters.highlighters.len();
+                        for language in languages {
+                            self.highlighters.languages.insert(language, i);
+                        }
+                        let highlighter = Highlighter::from_str(&source);
+                        self.highlighters.highlighters.push(highlighter);
+                    }
+                    languages = line.split('/').map(|s| s.trim().to_string()).collect();
+                    source.clear();
+                    continue;
+                }
+            }
+            source.push_str(line);
+            source.push('\n');
+        }
+        // Bank the current source.
+        if !languages.is_empty() {
+            let i = self.highlighters.highlighters.len();
+            for language in languages {
+                self.highlighters.languages.insert(language, i);
+            }
+            let highlighter = Highlighter::from_str(&source);
+            self.highlighters.highlighters.push(highlighter);
+        }
+    }
+
     // Ext is extension without a dot.
     // Checks if a relative link to an internal page name can be reached from
     // the current page, and returns a resolved absolute link to the page with extension.
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>"),