feat(lsp): add extension inference and improve diagnostics

🤖 Generated with assistance of OhMyOpenCode

src/tools/lsp/infer-extension.ts

@@ -0,0 +1,65 @@
+import { readdirSync, lstatSync } from "fs"
+import { extname, join } from "path"
+
+import { EXT_TO_LANG } from "./language-mappings"
+
+const SKIP_DIRECTORIES = new Set(["node_modules", ".git", "dist", "build", ".next", "out"])
+const MAX_SCAN_ENTRIES = 500
+
+export function inferExtensionFromDirectory(directory: string): string | null {
+  const extensionCounts = new Map<string, number>()
+  let scanned = 0
+
+  function walk(dir: string): void {
+    if (scanned >= MAX_SCAN_ENTRIES) return
+
+    let entries: string[]
+    try {
+      entries = readdirSync(dir)
+    } catch {
+      return
+    }
+
+    for (const entry of entries) {
+      if (scanned >= MAX_SCAN_ENTRIES) return
+
+      const fullPath = join(dir, entry)
+
+      let stat: ReturnType<typeof lstatSync> | undefined
+      try {
+        stat = lstatSync(fullPath)
+      } catch {
+        continue
+      }
+
+      if (stat.isSymbolicLink()) continue
+      scanned++
+
+      if (stat.isDirectory()) {
+        if (!SKIP_DIRECTORIES.has(entry)) {
+          walk(fullPath)
+        }
+      } else if (stat.isFile()) {
+        const ext = extname(fullPath)
+        if (ext && ext in EXT_TO_LANG) {
+          extensionCounts.set(ext, (extensionCounts.get(ext) ?? 0) + 1)
+        }
+      }
+    }
+  }
+
+  walk(directory)
+
+  if (extensionCounts.size === 0) return null
+
+  let maxExt = ""
+  let maxCount = 0
+  for (const [ext, count] of extensionCounts) {
+    if (count > maxCount) {
+      maxCount = count
+      maxExt = ext
+    }
+  }
+
+  return maxExt || null
+}