detect mermaid diagram

src/template.rs

@@ -22,7 +22,7 @@ enum FrontMatter<'a> {
 }
 
 impl FrontMatter<'_> {
-    fn parse(&self) -> Option<Metadata> {
+    fn parse(&self) -> Metadata {
         match self {
             Self::Yaml(val) => serde_yaml::from_str(val).unwrap_or_default(),
             Self::Toml(_val) => todo!(),
@@ -31,12 +31,13 @@ impl FrontMatter<'_> {
     }
 }
 
-#[derive(Deserialize)]
+#[derive(Default, Deserialize)]
 pub struct Metadata {
     pub title: Option<String>,
+    pub mermaid: bool,
 }
 
-pub fn read_md(filename: &str) -> (Option<Metadata>, String) {
+pub fn read_md(filename: &str) -> (Metadata, String) {
     // Read markdown file
     let mut text = std::fs::read_to_string(filename).unwrap();
 
@@ -59,11 +60,12 @@ pub fn read_md(filename: &str) -> (Option<Metadata>, String) {
     };
 
     let md_tree = markdown::to_mdast(&text, &parse_option).unwrap();
-    let metadata = match &md_tree.children().unwrap()[0] {
+    let md_nodes = md_tree.children().unwrap();
+    let metadata = match &md_nodes[0] {
         markdown::mdast::Node::Yaml(v) => FrontMatter::Yaml(&v.value).parse(),
         markdown::mdast::Node::Toml(v) => FrontMatter::Toml(&v.value).parse(),
         markdown::mdast::Node::MdxjsEsm(v) => FrontMatter::Json(&v.value).parse(),
-        _ => None,
+        _ => Metadata::default(),
     };
 
     // Convert to HTML
@@ -76,5 +78,23 @@ pub fn read_md(filename: &str) -> (Option<Metadata>, String) {
     )
     .unwrap();
 
-    (metadata, html)
+    // Find if document contains mermaid diagram
+    let presence_mermaid = md_nodes.iter().fold(false, |acc, x| {
+        if !acc {
+            match x {
+                markdown::mdast::Node::Code(code) => code.lang == Some(String::from("mermaid")),
+                _ => false,
+            }
+        } else {
+            false
+        }
+    });
+
+    (
+        Metadata {
+            mermaid: presence_mermaid,
+            ..metadata
+        },
+        html,
+    )
 }