Overridable config via CLI -o flag

docs/config.md

@@ -22,6 +22,11 @@ Configuration files are located in the application's configuration directory, wh
 A sample `app.toml` is available at [examples/app.toml](../examples/app.toml).
 
 `spotify_player` uses `app.toml` for application settings. Available options:
+`spotify_player` also supports cli config overriding using -o / --config-override flag. Example:
+
+```bash
+spotify_player -o device.volume=80 -o theme=dracula
+```
 
 | Option                            | Description                                                                                    | Default                                                                |
 | --------------------------------- | ---------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------- |

spotify_player/src/cli/mod.rs

@@ -201,6 +201,14 @@ pub fn init_cli() -> anyhow::Result<clap::Command> {
                 .value_name("FOLDER")
                 .default_value(default_cache_folder.into_os_string())
                 .help("Path to the application's cache folder"),
+        )
+        .arg(
+            clap::Arg::new("config-override")
+                .short('o')
+                .long("config-override")
+                .value_name("KEY=VALUE")
+                .action(clap::ArgAction::Append)
+                .help("Override a config option (e.g. -o device.volume=80 -o theme=dracula)"),
         );
 
     #[cfg(feature = "daemon")]

spotify_player/src/config/mod.rs

@@ -17,6 +17,7 @@ use std::{
     sync::OnceLock,
 };
 
+use anyhow::Context;
 use keymap::KeymapConfig;
 use theme::ThemeConfig;
 
@@ -517,3 +518,36 @@ pub fn set_config(configs: Configs) {
         .set(configs)
         .expect("configs should be initialized only once");
 }
+
+// Apply a CLI config override to the application config.
+// Serializes the config to TOML, navigates to the key via dot-notation,
+// overrides the value, and deserializes back into AppConfig.
+// Returns an error if the key path is invalid or the value type mismatches.
+pub fn apply_config_override(config: &mut AppConfig, key: &str, value: &str) -> anyhow::Result<()> {
+    let mut config_value = toml::Value::try_from(&*config)?;
+
+    let parts: Vec<&str> = key.split('.').collect();
+    let mut current = &mut config_value;
+
+    for (i, part) in parts.iter().enumerate() {
+        if i == parts.len() - 1 {
+            let table = current
+                .as_table_mut()
+                .context(format!("'{key}' is not a valid config path"))?;
+
+            let parsed_value: toml::Value = value
+                .parse()
+                .unwrap_or_else(|_| toml::Value::String(value.to_string()));
+
+            table.insert(part.to_string(), parsed_value);
+        } else {
+            current = current
+                .get_mut(part)
+                .context(format!("Config key '{part}' not found in path '{key}'"))?;
+        }
+    }
+
+    *config = config_value.try_into()?;
+
+    Ok(())
+}

spotify_player/src/main.rs

@@ -22,6 +22,8 @@ use std::{collections::VecDeque, io::Write, sync::Arc};
 use tracing_subscriber::layer::SubscriberExt;
 use tracing_subscriber::util::SubscriberInitExt;
 
+use crate::config::apply_config_override;
+
 fn init_spotify(
     client_pub: &flume::Sender<client::ClientRequest>,
     client: &client::AppClient,
@@ -270,9 +272,14 @@ fn main() -> Result<()> {
             // set the log folder to be the cache folder if it is not set
             configs.app_config.log_folder = Some(cache_folder);
         }
-        if let Some(theme) = args.get_one::<String>("theme") {
-            // override the theme config if user specifies a `theme` cli argument
-            theme.clone_into(&mut configs.app_config.theme);
+        if let Some(overrides) = args.get_many::<String>("config-override") {
+            for override_str in overrides {
+                let (key, value) = override_str.split_once('=').context(format!(
+                    "Invalid override format: '{override_str}'. Expected KEY=VALUE"
+                ))?;
+
+                apply_config_override(&mut configs.app_config, key, value)?;
+            }
         }
         config::set_config(configs);
     }