From 2b46656d3eab7286e60442f4e69351d009ac5737 Mon Sep 17 00:00:00 2001
From: Joseph O'Brien <98370624+89jobrien@users.noreply.github.com>
Date: Thu, 2 Apr 2026 02:26:53 -0400
Subject: [PATCH] feat(notgraph): implement module_graph collector

---
 crates/notgraph/src/lib.rs                    |   1 +
 crates/notgraph/src/module_graph.rs           | 105 ++++++++++++++++++
 .../tests/fixtures/clean/src/alpha.rs         |   1 +
 .../notgraph/tests/fixtures/clean/src/beta.rs |   1 +
 .../notgraph/tests/fixtures/clean/src/lib.rs  |   2 +
 5 files changed, 110 insertions(+)
 create mode 100644 crates/notgraph/src/module_graph.rs
 create mode 100644 crates/notgraph/tests/fixtures/clean/src/alpha.rs
 create mode 100644 crates/notgraph/tests/fixtures/clean/src/beta.rs
 create mode 100644 crates/notgraph/tests/fixtures/clean/src/lib.rs

diff --git a/crates/notgraph/src/lib.rs b/crates/notgraph/src/lib.rs
index 02a3c82..b82ac0f 100644
--- a/crates/notgraph/src/lib.rs
+++ b/crates/notgraph/src/lib.rs
@@ -1,2 +1,3 @@
 pub mod crate_graph;
+pub mod module_graph;
 pub mod types;
diff --git a/crates/notgraph/src/module_graph.rs b/crates/notgraph/src/module_graph.rs
new file mode 100644
index 0000000..ca184c1
--- /dev/null
+++ b/crates/notgraph/src/module_graph.rs
@@ -0,0 +1,105 @@
+use crate::types::{CrateName, ModPath, ModuleGraph};
+use anyhow::Result;
+use std::path::Path;
+use syn::visit::Visit;
+use walkdir::WalkDir;
+
+struct ModCollector {
+    current_mod: ModPath,
+    edges: Vec<(ModPath, ModPath)>,
+    nodes: Vec<ModPath>,
+}
+
+impl ModCollector {
+    fn new(root_mod: ModPath) -> Self {
+        Self {
+            current_mod: root_mod.clone(),
+            edges: Vec::new(),
+            nodes: vec![root_mod],
+        }
+    }
+}
+
+impl<'ast> Visit<'ast> for ModCollector {
+    fn visit_item_mod(&mut self, node: &'ast syn::ItemMod) {
+        let child = format!("{}::{}", self.current_mod, node.ident);
+        if !self.nodes.contains(&child) {
+            self.nodes.push(child.clone());
+        }
+        self.edges.push((self.current_mod.clone(), child.clone()));
+        let parent = std::mem::replace(&mut self.current_mod, child);
+        syn::visit::visit_item_mod(self, node);
+        self.current_mod = parent;
+    }
+}
+
+fn path_to_mod(krate: &str, rel: &Path) -> ModPath {
+    let mut parts: Vec<String> = vec![krate.to_string()];
+    for component in rel.components() {
+        let s = component.as_os_str().to_string_lossy();
+        if s == "lib.rs" || s == "main.rs" {
+            break;
+        }
+        let s = s.trim_end_matches(".rs").to_string();
+        if s != "mod" {
+            parts.push(s);
+        }
+    }
+    parts.join("::")
+}
+
+pub fn build(krate: CrateName, src_dir: &Path) -> Result<ModuleGraph> {
+    let mut all_nodes: Vec<ModPath> = Vec::new();
+    let mut all_edges: Vec<(ModPath, ModPath)> = Vec::new();
+
+    for entry in WalkDir::new(src_dir)
+        .into_iter()
+        .filter_map(|e| e.ok())
+        .filter(|e| e.path().extension().map_or(false, |x| x == "rs"))
+    {
+        let path = entry.path();
+        let content = std::fs::read_to_string(path)?;
+        let file = syn::parse_file(&content)?;
+        let rel = path.strip_prefix(src_dir)?;
+        let mod_path = path_to_mod(&krate, rel);
+
+        let mut collector = ModCollector::new(mod_path);
+        collector.visit_file(&file);
+
+        for node in collector.nodes {
+            if !all_nodes.contains(&node) {
+                all_nodes.push(node);
+            }
+        }
+        all_edges.extend(collector.edges);
+    }
+
+    all_edges.sort();
+    all_edges.dedup();
+
+    Ok(ModuleGraph { krate, nodes: all_nodes, edges: all_edges })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn clean_fixture_has_expected_nodes() {
+        let fixture = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("tests/fixtures/clean/src");
+        let graph = build("clean".to_string(), &fixture).unwrap();
+        assert!(graph.nodes.contains(&"clean".to_string()));
+        assert!(graph.nodes.contains(&"clean::alpha".to_string()));
+        assert!(graph.nodes.contains(&"clean::beta".to_string()));
+    }
+
+    #[test]
+    fn clean_fixture_has_edges_from_lib() {
+        let fixture = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("tests/fixtures/clean/src");
+        let graph = build("clean".to_string(), &fixture).unwrap();
+        assert!(graph.edges.contains(&("clean".to_string(), "clean::alpha".to_string())));
+        assert!(graph.edges.contains(&("clean".to_string(), "clean::beta".to_string())));
+    }
+}
diff --git a/crates/notgraph/tests/fixtures/clean/src/alpha.rs b/crates/notgraph/tests/fixtures/clean/src/alpha.rs
new file mode 100644
index 0000000..c340dba
--- /dev/null
+++ b/crates/notgraph/tests/fixtures/clean/src/alpha.rs
@@ -0,0 +1 @@
+pub fn hello() -> &'static str { "alpha" }
diff --git a/crates/notgraph/tests/fixtures/clean/src/beta.rs b/crates/notgraph/tests/fixtures/clean/src/beta.rs
new file mode 100644
index 0000000..0930fde
--- /dev/null
+++ b/crates/notgraph/tests/fixtures/clean/src/beta.rs
@@ -0,0 +1 @@
+pub fn greet() -> &'static str { "beta" }
diff --git a/crates/notgraph/tests/fixtures/clean/src/lib.rs b/crates/notgraph/tests/fixtures/clean/src/lib.rs
new file mode 100644
index 0000000..cfa8271
--- /dev/null
+++ b/crates/notgraph/tests/fixtures/clean/src/lib.rs
@@ -0,0 +1,2 @@
+pub mod alpha;
+pub mod beta;