feat: tab completions for file paths (#279)

Made a PR as was requested in the #113

codex-cli/src/utils/file-system-suggestions.ts

@@ -0,0 +1,42 @@
+import fs from "fs";
+import os from "os";
+import path from "path";
+
+export function getFileSystemSuggestions(pathPrefix: string): Array<string> {
+  if (!pathPrefix) {
+    return [];
+  }
+
+  try {
+    const sep = path.sep;
+    const hasTilde = pathPrefix === "~" || pathPrefix.startsWith("~" + sep);
+    const expanded = hasTilde
+      ? path.join(os.homedir(), pathPrefix.slice(1))
+      : pathPrefix;
+
+    const normalized = path.normalize(expanded);
+    const isDir = pathPrefix.endsWith(path.sep);
+    const base = path.basename(normalized);
+
+    const dir =
+      normalized === "." && !pathPrefix.startsWith("." + sep) && !hasTilde
+        ? process.cwd()
+        : path.dirname(normalized);
+
+    const readDir = isDir ? path.join(dir, base) : dir;
+
+    return fs
+      .readdirSync(readDir)
+      .filter((item) => isDir || item.startsWith(base))
+      .map((item) => {
+        const fullPath = path.join(readDir, item);
+        const isDirectory = fs.statSync(fullPath).isDirectory();
+        if (isDirectory) {
+          return path.join(fullPath, sep);
+        }
+        return fullPath;
+      });
+  } catch {
+    return [];
+  }
+}