initial commit

helpers/mdbook-exercise-linker/src/lib.rs

@@ -0,0 +1,75 @@
+use anyhow::{Context, Error};
+use mdbook::book::Book;
+use mdbook::preprocess::{Preprocessor, PreprocessorContext};
+use mdbook::BookItem;
+
+pub struct ExerciseLinker;
+
+impl ExerciseLinker {
+    pub fn new() -> ExerciseLinker {
+        ExerciseLinker
+    }
+}
+
+impl Preprocessor for ExerciseLinker {
+    fn name(&self) -> &str {
+        "exercise-linker"
+    }
+
+    fn run(&self, ctx: &PreprocessorContext, mut book: Book) -> Result<Book, Error> {
+        let config = ctx
+            .config
+            .get_preprocessor(self.name())
+            .context("Failed to get preprocessor configuration")?;
+        let key = String::from("exercise_root_url");
+        let root_url = config
+            .get(&key)
+            .context("Failed to get `exercise_root_url`")?;
+        let root_url = root_url
+            .as_str()
+            .context("`exercise_root_url` is not a string")?
+            .to_owned();
+
+        book.sections
+            .iter_mut()
+            .for_each(|i| process_book_item(i, &ctx.renderer, &root_url));
+        Ok(book)
+    }
+
+    fn supports_renderer(&self, _renderer: &str) -> bool {
+        true
+    }
+}
+
+fn process_book_item(item: &mut BookItem, renderer: &str, root_url: &str) {
+    match item {
+        BookItem::Chapter(chapter) => {
+            chapter.sub_items.iter_mut().for_each(|item| {
+                process_book_item(item, renderer, root_url);
+            });
+
+            let Some(source_path) = &chapter.source_path else {
+                return;
+            };
+            let source_path = source_path.display().to_string();
+
+            // Ignore non-exercise chapters
+            if !source_path.chars().take(2).all(|c| c.is_digit(10)) {
+                return;
+            }
+
+            let exercise_path = source_path.strip_suffix(".md").unwrap();
+            let link_section = format!(
+                    "\n## Exercise\n\nThe exercise for this section is located in [`{exercise_path}`]({})\n",
+                    format!("{}/{}", root_url, exercise_path)
+                );
+            chapter.content.push_str(&link_section);
+
+            if renderer == "pandoc" {
+                chapter.content.push_str("`\\newpage`{=latex}\n");
+            }
+        }
+        BookItem::Separator => {}
+        BookItem::PartTitle(_) => {}
+    }
+}