1 files changed, 102 insertions, 0 deletions
diff --git a/crates/typst-docs/src/link.rs b/crates/typst-docs/src/link.rs
new file mode 100644
index 00000000..5d7a5485
--- /dev/null
+++ b/crates/typst-docs/src/link.rs
@@ -0,0 +1,102 @@
+use typst::diag::{bail, StrResult};
+use typst::eval::Func;
+
+use super::{get_module, GROUPS, LIBRARY};
+
+/// Resolve an intra-doc link.
+pub fn resolve(link: &str) -> StrResult<String> {
+    if link.starts_with('#') || link.starts_with("http") {
+        return Ok(link.to_string());
+    }
+
+    let (head, tail) = split_link(link)?;
+    let mut route = match resolve_known(head) {
+        Some(route) => route.into(),
+        None => resolve_definition(head)?,
+    };
+
+    if !tail.is_empty() {
+        route.push('/');
+        route.push_str(tail);
+    }
+
+    if !route.contains('#') && !route.ends_with('/') {
+        route.push('/');
+    }
+
+    Ok(route)
+}
+
+/// Split a link at the first slash.
+fn split_link(link: &str) -> StrResult<(&str, &str)> {
+    let first = link.split('/').next().unwrap_or(link);
+    let rest = link[first.len()..].trim_start_matches('/');
+    Ok((first, rest))
+}
+
+/// Resolve a `$` link head to a known destination.
+fn resolve_known(head: &str) -> Option<&'static str> {
+    Some(match head {
+        "$tutorial" => "/docs/tutorial/",
+        "$reference" => "/docs/reference/",
+        "$category" => "/docs/reference/",
+        "$syntax" => "/docs/reference/syntax/",
+        "$styling" => "/docs/reference/styling/",
+        "$scripting" => "/docs/reference/scripting/",
+        "$guides" => "/docs/guides/",
+        "$packages" => "/docs/packages/",
+        "$changelog" => "/docs/changelog/",
+        "$community" => "/docs/community/",
+        _ => return None,
+    })
+}
+
+/// Resolve a `$` link to a global definition.
+fn resolve_definition(head: &str) -> StrResult<String> {
+    let mut parts = head.trim_start_matches('$').split('.').peekable();
+    let mut focus = &LIBRARY.global;
+    while let Some(m) = parts.peek().and_then(|&name| get_module(focus, name).ok()) {
+        focus = m;
+        parts.next();
+    }
+
+    let name = parts.next().ok_or("link is missing first part")?;
+    let value = focus.field(name)?;
+    let Some(category) = focus.scope().get_category(name) else {
+        bail!("{name} has no category");
+    };
+
+    // Handle grouped functions.
+    if let Some(group) = GROUPS
+        .iter()
+        .filter(|_| category == "math")
+        .find(|group| group.functions.iter().any(|func| func == name))
+    {
+        let mut route =
+            format!("/docs/reference/math/{}/#functions-{}", group.name, name);
+        if let Some(param) = parts.next() {
+            route.push('-');
+            route.push_str(param);
+        }
+        return Ok(route);
+    }
+
+    let mut route = format!("/docs/reference/{category}/{name}/");
+    if let Some(next) = parts.next() {
+        if value.field(next).is_ok() {
+            route.push_str("#definitions-");
+            route.push_str(next);
+        } else if value
+            .clone()
+            .cast::<Func>()
+            .map_or(false, |func| func.param(next).is_some())
+        {
+            route.push_str("#parameters-");
+            route.push_str(next);
+        } else {
+            bail!("field {next} not found");
+        }
+    }
+
+    Ok(route)
+}