webmentions: check webmentions and save them to the database

1 files changed, 104 insertions, 0 deletions

diff --git a/kittybox-rs/src/webmentions/check.rs b/kittybox-rs/src/webmentions/check.rs
new file mode 100644
index 0000000..eb4afcf
--- /dev/null
+++ b/kittybox-rs/src/webmentions/check.rs
@@ -0,0 +1,104 @@
+use std::{cell::RefCell, rc::Rc};
+use microformats::{types::PropertyValue, html5ever::{self, tendril::TendrilSink}};
+use kittybox_util::MentionType;
+
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("microformats error: {0}")]
+    Microformats(#[from] microformats::Error),
+    // #[error("json error: {0}")]
+    // Json(#[from] serde_json::Error),
+    #[error("url parse error: {0}")]
+    UrlParse(#[from] url::ParseError),
+}
+
+pub fn check_mention(document: impl AsRef<str>, base_url: &url::Url, link: &url::Url) -> Result<Option<(MentionType, serde_json::Value)>, Error> {
+    // First, check the document for MF2 markup
+    let document = microformats::from_html(document.as_ref(), base_url.clone())?;
+
+    // Get an iterator of all items
+    let items_iter = document.items.iter()
+        .map(AsRef::as_ref)
+        .map(RefCell::borrow);
+
+    for item in items_iter {
+        let props = item.properties.borrow();
+        for (prop, interaction_type) in [
+            ("in-reply-to", MentionType::Reply), ("like-of", MentionType::Like),
+            ("bookmark-of", MentionType::Bookmark), ("repost-of", MentionType::Repost)
+        ] {
+            if let Some(propvals) = props.get(prop) {
+                for val in propvals {
+                    if let PropertyValue::Url(url) = val {
+                        if url == link {
+                            return Ok(Some((interaction_type, serde_json::to_value(&*item).unwrap())))
+                        }
+                    }
+                }
+            }
+        }
+        // Process `content`
+        if let Some(PropertyValue::Fragment(content)) = props.get("content")
+            .map(Vec::as_slice)
+            .unwrap_or_default()
+            .first()
+        {
+            let root = html5ever::parse_document(html5ever::rcdom::RcDom::default(), Default::default())
+                .from_utf8()
+                .one(content.html.to_owned().as_bytes())
+                .document;
+
+            // This is a trick to unwrap recursion into a loop
+            //
+            // A list of unprocessed node is made. Then, in each
+            // iteration, the list is "taken" and replaced with an
+            // empty list, which is populated with nodes for the next
+            // iteration of the loop.
+            //
+            // Empty list means all nodes were processed.
+            let mut unprocessed_nodes: Vec<Rc<html5ever::rcdom::Node>> = root.children.borrow().iter().cloned().collect();
+            while !unprocessed_nodes.is_empty() {
+                // "Take" the list out of its memory slot, replace it with an empty list
+                let nodes = std::mem::take(&mut unprocessed_nodes);
+                'nodes_loop: for node in nodes.into_iter() {
+                    // Add children nodes to the list for the next iteration
+                    unprocessed_nodes.extend(node.children.borrow().iter().cloned());
+
+                    if let html5ever::rcdom::NodeData::Element { ref name, ref attrs, .. } = node.data {
+                        // If it's not `<a>`, skip it
+                        if name.local != *"a" { continue; }
+                        let mut is_mention: bool = false;
+                        for attr in attrs.borrow().iter() {
+                            if attr.name.local == *"rel" {
+                                // Don't count `rel="nofollow"` links — a web crawler should ignore them
+                                // and so for purposes of driving visitors they are useless
+                                if attr.value
+                                    .as_ref()
+                                    .split([',', ' '])
+                                    .any(|v| v == "nofollow")
+                                {
+                                    // Skip the entire node.
+                                    continue 'nodes_loop;
+                                }
+                            }
+                            // if it's not `<a href="...">`, skip it 
+                            if attr.name.local != *"href" { continue; }
+                            // Be forgiving in parsing URLs, and resolve them against the base URL
+                            if let Ok(url) = base_url.join(attr.value.as_ref()) {
+                                if &url == link {
+                                    is_mention = true;
+                                }
+                            }
+                        }
+                        if is_mention {
+                            return Ok(Some((MentionType::Mention, serde_json::to_value(&*item).unwrap())));
+                        }
+                    }
+                }
+            }
+            
+        }
+    }
+
+    Ok(None)
+}