feat(config): Improve user configuration handling

- Refactor user configuration loading to ensure the config directory is created if it doesn't exist.
- Read the blueprint configuration and merge missing keys into the user config, updating the file only if changes are made.
- Enhance error handling for reading and writing configuration files, ensuring a smoother user experience.

Author: heroheman

src/config.rs

@@ -31,23 +31,45 @@ impl Settings {
 
         let user_config_path = get_user_config_path();
 
-        // If the user config doesn't exist, create it from the blueprint `whid.toml`
-        if !user_config_path.exists() {
-            // Use the determined blueprint path to read the content
-            if let Ok(blueprint_content) = fs::read_to_string(&blueprint_path) {
-                if let Some(parent) = user_config_path.parent() {
-                    fs::create_dir_all(parent).expect("Could not create config directory");
-                }
-                fs::write(&user_config_path, blueprint_content)
-                    .expect("Could not write user config file from blueprint");
+        // Ensure the user config directory exists
+        if let Some(parent) = user_config_path.parent() {
+            if !parent.exists() {
+                fs::create_dir_all(parent).expect("Could not create config directory");
             }
-            // If whid.toml doesn't exist at blueprint_path, builder will fail. This is intended.
         }
 
+        // Read the blueprint
+        let blueprint_content = fs::read_to_string(&blueprint_path)
+            .expect("Could not read blueprint config file");
+        let blueprint_table: toml::Table = blueprint_content.parse()
+            .expect("Could not parse blueprint config as TOML");
+
+        // Read the user config, or create an empty table if it doesn't exist
+        let user_config_content = fs::read_to_string(&user_config_path).unwrap_or_default();
+        let mut user_table: toml::Table = user_config_content.parse()
+            .unwrap_or_else(|_| toml::Table::new());
+
+        let mut config_was_updated = false;
+        // Iterate over the blueprint and add missing keys to the user config
+        for (key, value) in blueprint_table.iter() {
+            if !user_table.contains_key(key) {
+                user_table.insert(key.clone(), value.clone());
+                config_was_updated = true;
+            }
+        }
+
+        // If the user config was modified, write it back to the file
+        if config_was_updated || !user_config_path.exists() {
+            fs::write(&user_config_path, user_table.to_string())
+                .expect("Could not write updated user config file");
+        }
+
+
         let s = Config::builder()
             // 1. Load project defaults from whid.toml (blueprint). Required.
+            // This still acts as the base for deserialization structure.
             .add_source(File::from(blueprint_path).required(true))
-            // 2. Merge user's global config. Required as we just created it if it was missing.
+            // 2. Merge user's global config.
             .add_source(File::from(user_config_path).required(true))
             // 3. Merge local whid.toml from CWD. Optional override.
             .add_source(File::with_name("whid.toml").required(false))