lemmy/crates/utils/src/utils/markdown/link_rule.rs

use markdown_it::{generics::inline::full_link, MarkdownIt, Node, NodeValue, Renderer};

/// Renders markdown links. Copied directly from markdown-it source, unlike original code it also
/// sets `rel=nofollow` attribute.
///
/// TODO: We can set nofollow only if post was not made by mod/admin, but then we have to construct
///       new parser for every invocation which might have performance implications.
/// https://github.com/markdown-it-rust/markdown-it/blob/master/src/plugins/cmark/inline/link.rs
#[derive(Debug)]
pub struct Link {
  pub url: String,
  pub title: Option<String>,
}

impl NodeValue for Link {
  fn render(&self, node: &Node, fmt: &mut dyn Renderer) {
    let mut attrs = node.attrs.clone();
    attrs.push(("href", self.url.clone()));
    attrs.push(("rel", "nofollow".to_string()));

    if let Some(title) = &self.title {
      attrs.push(("title", title.clone()));
    }

    fmt.open("a", &attrs);
    fmt.contents(&node.children);
    fmt.close("a");
  }
}

pub fn add(md: &mut MarkdownIt) {
  full_link::add::<false>(md, |href, title| {
    Node::new(Link {
      url: href.unwrap_or_default(),
      title,
    })
  });
}