diff --git a/src/main.rs b/src/main.rs
index f0218a6..c4e41dc 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -65,49 +65,61 @@ fn rename_files(directory: &str, base: &str, args: &Arguments) -> Result<i32> {
             if let Some(sub_dir) = path.to_str() {
                 count += rename_files(sub_dir, base, args).context("Failed to rename files")?;
             }
-        }
-        if !path.is_file() {
-            continue;
-        }
-        let Ok(file) = taglib::File::new(&path) else {
-            continue;
-        };
-        let Ok(tag) = file.tag() else {
-            continue;
-        };
-        let (Some(title), Some(artist)) = (tag.title(), tag.artist()) else {
-            continue;
-        };
-        let (bucket, _) = artist.split_at(1);
-        let album = parse_album(&title);
-        count += 1;
-        let new_name = if album.is_empty() {
-            format!("{bucket}/{artist}/{title}/{title}.m4b")
-        } else {
-            build_series_name(bucket, &artist, &album, &title)
-        };
-        println!("==============================");
-        println!("- artist: {artist}");
-        println!("- album : {album}");
-        println!("- title : {title}");
-        println!("> {new_name}");
-        if args.not_dry_run() {
-            let target_path = Path::new(&base).join(new_name);
-            if !target_path.exists() {
-                let dir = target_path
-                    .parent()
-                    .with_context(|| format!("Failed to get parent: {:#?}", target_path))?;
-                create_dir_all(dir)
-                    .with_context(|| format!("Failed to create directory: {:#?}", dir))?;
+        } else if path.is_file() {
+            let Some((title, artist)) = find_tag_info(&path) else {
+                continue;
+            };
+            let (bucket, _) = artist.split_at(1);
+            let album = parse_album(&title);
+            count += 1;
+            let new_name = if album.is_empty() {
+                format!("{bucket}/{artist}/{title}/{title}.m4b")
+            } else {
+                build_series_name(bucket, &artist, &album, &title)
+            };
+            println!("==============================");
+            println!("- artist: {artist}");
+            println!("- album : {album}");
+            println!("- title : {title}");
+            println!("> {new_name}");
+            if args.not_dry_run() {
+                rename_file(base, new_name, path)?;
             }
-
-            rename(&path, &target_path)
-                .with_context(|| format!("Failed to rename file: {:#?}", target_path))?;
         }
     }
     Ok(count)
 }
 
+fn find_tag_info(path: &std::path::PathBuf) -> Option<(String, String)> {
+    let Ok(file) = taglib::File::new(path) else {
+        return None;
+    };
+    let Ok(tag) = file.tag() else {
+        return None;
+    };
+    let (Some(title), Some(artist)) = (tag.title(), tag.artist()) else {
+        return None;
+    };
+    Some((title, artist))
+}
+
+fn rename_file(
+    base: &str,
+    new_name: String,
+    path: std::path::PathBuf,
+) -> Result<(), anyhow::Error> {
+    let target_path = Path::new(&base).join(new_name);
+    if !target_path.exists() {
+        let dir = target_path
+            .parent()
+            .with_context(|| format!("Failed to get parent: {:#?}", target_path))?;
+        create_dir_all(dir).with_context(|| format!("Failed to create directory: {:#?}", dir))?;
+    }
+    rename(&path, &target_path)
+        .with_context(|| format!("Failed to rename file: {:#?}", target_path))?;
+    Ok(())
+}
+
 fn build_series_name(bucket: &str, artist: &str, album: &str, title: &str) -> String {
     let index = parse_index(title);
     let title = parse_title(title);