feat: support user preview configuration and document UI

crates/latchd-core/src/config.rs

@@ -1,6 +1,6 @@
 use std::{
     collections::HashMap,
-    fs,
+    env, fs,
     os::unix::fs::MetadataExt,
     path::{Path, PathBuf},
 };
@@ -9,6 +9,19 @@ use serde::Deserialize;
 
 use crate::error::{Error, ResultExt};
 
+pub const SYSTEM_CONFIG_PATH: &str = "/etc/latchd/config.toml";
+const PROJECT_CONFIG_DIR: &str = "latchd";
+const CONFIG_FILE: &str = "config.toml";
+
+/// Returns the current user's configuration path.
+pub fn user_config_path() -> Option<PathBuf> {
+    let base = env::var_os("XDG_CONFIG_HOME")
+        .map(PathBuf::from)
+        .filter(|path| path.is_absolute())
+        .or_else(|| env::var_os("HOME").map(|home| PathBuf::from(home).join(".config")))?;
+    Some(base.join(PROJECT_CONFIG_DIR).join(CONFIG_FILE))
+}
+
 #[derive(Debug, Clone, Deserialize)]
 #[serde(default, deny_unknown_fields)]
 pub struct Config {