feat: extract card image from html if not defined

example/content/2024-10-19-what-is-marmite-static-site-generator.md

@@ -157,6 +157,12 @@ Content
       - tag2
     ```
   **default** empty
+
+**card_image**
+
+  : Image url to use as social card image `og:image`  
+  **format**  `./media/file.png` or `https://path/to/img.jpg`  
+  **default** first image extracted from html content, config card_image, or None.
 
 **extra**
 

example/content/customizing-templates.md

@@ -68,6 +68,7 @@ date: DateTimeObject or None
 extra: {key: value}
 links_to: [str] or None
 back_links: [Content] or []
+card_image: str or None
 ```
 
 There are 6 templates inside the `templates` folder, each adds more data to context.

example/templates/content.html

@@ -7,8 +7,8 @@
 {% else %}
 <meta property="og:description" content="{{ content.html | striptags | trim_start_matches(pat=content.title) | truncate(length=100, end="...") }}">
 {%- endif %}
-{% if content.extra.card_image %}
-<meta property="og:image" content="{{url_for(path=content.extra.card_image, abs=true)}}">
+{% if content.card_image %}
+<meta property="og:image" content="{{url_for(path=content.card_image, abs=true)}}">
 {% elif site.card_image %}
 <meta property="og:image" content="{{url_for(path=site.card_image, abs=true)}}">
 {% endif %}

src/content.rs

@@ -20,6 +20,7 @@ pub struct Content {
     pub extra: Option<Value>,
     pub links_to: Option<Vec<String>>,
     pub back_links: Vec<Self>,
+    pub card_image: Option<String>,
 }
 
 pub fn get_title<'a>(frontmatter: &'a Frontmatter, html: &'a str) -> String {

src/markdown.rs

@@ -29,6 +29,7 @@ pub fn get_content(path: &Path) -> Result<Content, String> {
     let extra = frontmatter.get("extra").map(std::borrow::ToOwned::to_owned);
     let links_to = get_links_to(&html);
     let back_links = Vec::new(); // will be mutated later
+    let card_image = get_card_image(&frontmatter, &html);
     let content = Content {
         title,
         description,
@@ -39,10 +40,24 @@ pub fn get_content(path: &Path) -> Result<Content, String> {
         extra,
         links_to,
         back_links,
+        card_image,
     };
     Ok(content)
 }
 
+/// Capture `card_image` from frontmatter, then if not defined
+/// take the first img src found in the post content
+fn get_card_image(frontmatter: &Frontmatter, html: &str) -> Option<String> {
+    if let Some(card_image) = frontmatter.get("card_image") {
+        return Some(card_image.to_string());
+    }
+    // first <img> src attribute
+    let img_regex = Regex::new(r#"<img[^>]*src="([^"]+)""#).unwrap();
+    img_regex
+        .captures(html)
+        .and_then(|caps| caps.get(1).map(|m| m.as_str().to_string()))
+}
+
 fn get_links_to(html: &str) -> Option<Vec<String>> {
     let mut result = Vec::new();
     let re = Regex::new(r#"href="\./(.*?)\.html""#).unwrap();

src/site.rs

@@ -564,6 +564,7 @@ fn handle_404(
         tags: vec![],
         links_to: None,
         back_links: vec![],
+        card_image: None,
     };
     if input_404_path.exists() {
         let custom_content = get_content(&input_404_path)?;

src/tera_functions.rs

@@ -14,6 +14,7 @@ impl Function for UrlFor {
             .get("path")
             .and_then(Value::as_str)
             .ok_or_else(|| tera::Error::msg("Missing `path` argument"))?
+            .trim_start_matches("./")
             .to_string();
 
         let abs_prefixes = ["http", "https", "mailto"];