✨ feat(utils): create assure_config_dir_exists function

- add utility function to create config directory if it doesn't exist
- handle home directory expansion and error conditions

src/utils.rs

@@ -0,0 +1,38 @@
+use std::{env, fs, io};
+
+use crate::Error;
+
+pub(crate) fn assure_config_dir_exists(dir: &str) -> Result<String, Error> {
+    let trdir = dir.trim();
+    if trdir.is_empty() {
+        return Err(Error::DirectoryUnset);
+    }
+
+    let expanded_config_dir = if trdir.as_bytes()[0] == b'~' {
+        match env::var("HOME")
+            .ok()
+            .or_else(|| env::var("UserProfile").ok())
+        {
+            None => {
+                return Err(Error::HomeExpansionFailed(trdir.to_string()));
+            }
+            Some(mut user) => {
+                user.push_str(&trdir[1..]);
+                user
+            }
+        }
+    } else {
+        trdir.to_string()
+    };
+
+    if let Err(err) = fs::create_dir(&expanded_config_dir) {
+        if err.kind() != io::ErrorKind::AlreadyExists {
+            return Err(Error::DirectoryCreationFailed((
+                expanded_config_dir,
+                Box::new(err),
+            )));
+        }
+    }
+
+    Ok(expanded_config_dir)
+}