Add helper to find runtime

Author: nojaf

.prettierignore

@@ -2,4 +2,5 @@
 server/out
 analysis/examples
 analysis/reanalyze/examples
-tools/tests
+tools/tests
+.history/

server/src/find-runtime.ts

@@ -0,0 +1,121 @@
+import { readdir, stat as statAsync } from "fs/promises";
+import { join } from "path";
+
+// Efficient parallel folder traversal to find node_modules directories
+async function findNodeModulesDirs(
+  rootPath: string,
+  maxDepth = 12,
+): Promise<string[]> {
+  const nodeModulesDirs: string[] = [];
+  const stack: Array<{ dir: string; depth: number }> = [
+    { dir: rootPath, depth: 0 },
+  ];
+  const visited = new Set<string>();
+
+  while (stack.length) {
+    const { dir, depth } = stack.pop()!;
+    if (depth > maxDepth || visited.has(dir)) continue;
+    visited.add(dir);
+
+    let entries: string[];
+    try {
+      entries = await readdir(dir);
+    } catch {
+      continue;
+    }
+
+    if (entries.includes("node_modules")) {
+      const nm = join(dir, "node_modules");
+      try {
+        const st = await statAsync(nm);
+        if (st.isDirectory()) {
+          nodeModulesDirs.push(nm);
+          // Do NOT push deeper here to keep same behavior (stop at first node_modules in this branch)
+          continue;
+        }
+      } catch {}
+    }
+
+    for (const entry of entries) {
+      if (entry === "node_modules" || entry.startsWith(".")) continue;
+      const full = join(dir, entry);
+      try {
+        const st = await statAsync(full);
+        if (st.isDirectory()) {
+          stack.push({ dir: full, depth: depth + 1 });
+        }
+      } catch {}
+    }
+  }
+
+  return nodeModulesDirs;
+}
+
+// Custom function to find Deno vendorized @rescript/runtime directories
+async function findDenoRescriptRuntime(nodeModulesPath: string) {
+  // We only care about the Deno vendorized layout:
+  // <nodeModulesPath>/.deno/@rescript+runtime@<version>/node_modules/@rescript/runtime
+  const denoRoot = join(nodeModulesPath, ".deno");
+  let entries: string[];
+  try {
+    entries = await readdir(denoRoot);
+  } catch {
+    return [];
+  }
+
+  // Collect all @rescript+runtime@<version> vendor dirs
+  const vendorDirs = entries.filter((e) => e.startsWith("@rescript+runtime@"));
+  if (vendorDirs.length === 0) return [];
+
+  // Optionally pick “latest” by version; for now we return all valid matches.
+  const results: string[] = [];
+  for (const dir of vendorDirs) {
+    const runtimePath = join(
+      denoRoot,
+      dir,
+      "node_modules",
+      "@rescript",
+      "runtime",
+    );
+    try {
+      const st = await statAsync(runtimePath);
+      if (st.isDirectory()) results.push(runtimePath);
+    } catch {
+      // Ignore inaccessible / missing path
+    }
+  }
+
+  return results;
+}
+
+export async function findRuntime(project: string) {
+  // Find all node_modules directories using efficient traversal
+  const node_modules = await findNodeModulesDirs(project);
+
+  const rescriptRuntimeDirs = await Promise.all(
+    node_modules.map(async (nm) => {
+      const results = [];
+
+      // Check for standard layout: @rescript/runtime
+      const standardPath = join(nm, "@rescript", "runtime");
+      try {
+        const stat = await statAsync(standardPath);
+        if (stat.isDirectory()) {
+          results.push(standardPath);
+          // If we found standard layout, no need to search for Deno layouts
+          return results;
+        }
+      } catch (e) {
+        // Directory doesn't exist, continue
+      }
+
+      // Only check for Deno vendorized layouts if standard layout wasn't found
+      const denoResults = await findDenoRescriptRuntime(nm);
+      results.push(...denoResults);
+
+      return results;
+    }),
+  ).then((results) => results.flatMap((x) => x));
+
+  return rescriptRuntimeDirs;
+}