feat: configure sidebar min/max width via [ui] (#135)

* feat: configure sidebar min/max width via [ui]

Expose the previously hardcoded MIN_SIDEBAR_WIDTH / MAX_SIDEBAR_WIDTH
clamps as [ui] sidebar_min_width / sidebar_max_width. Defaults remain
18 / 36 so existing configs are unchanged. Hot-reload is wired through
the existing [ui] block; reload re-clamps the live width to the new
bounds so tightening takes effect immediately.

Reject inverted bounds (min > max) at every entry point so a bad config
can never reach u16::clamp(min, max), which panics: App::new falls back
to defaults, and apply_live_config treats the whole [ui] section as
invalid and returns a partial reload report.

refs #132

* test: keep sidebar reload width within bounds

refs #132

---------

Co-authored-by: Ogulcan Celik <ogulcancelik@gmail.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/src/config/model.rs b/src/config/model.rs
index 60a8859c..673eec02 100644
--- a/src/config/model.rs
+++ b/src/config/model.rs
@@ -48,6 +48,19 @@ pub struct ConfigReloadReport {
     pub diagnostics: Vec<String>,
 }
 
+/// Validate `[ui]` sidebar bound configuration.
+///
+/// Returns `Some((min, max))` when `min <= max`, `None` otherwise. The two
+/// values are funneled through this helper before they reach any
+/// `u16::clamp(min, max)` call site (`u16::clamp` panics when `min > max`).
+pub fn validated_sidebar_bounds(min: u16, max: u16) -> Option<(u16, u16)> {
+    if min <= max {
+        Some((min, max))
+    } else {
+        None
+    }
+}
+
 #[derive(Debug, Default, Deserialize)]
 #[serde(default)]
 pub struct Config {
@@ -147,6 +160,10 @@ pub struct IndexedKeysConfig {
 #[serde(default)]
 pub struct UiConfig {
     pub sidebar_width: u16,
+    /// Minimum sidebar width (columns) when expanded. Default: 18.
+    pub sidebar_min_width: u16,
+    /// Maximum sidebar width (columns) when expanded. Default: 36.
+    pub sidebar_max_width: u16,
     /// Capture mouse input for Herdr's mouse UI. Default: true.
     pub mouse_capture: bool,
     /// Ask for confirmation before closing a workspace. Default: true.
@@ -224,6 +241,8 @@ impl Default for UiConfig {
     fn default() -> Self {
         Self {
             sidebar_width: 26,
+            sidebar_min_width: 18,
+            sidebar_max_width: 36,
             mouse_capture: true,
             confirm_close: true,
             prompt_new_tab_name: true,
@@ -315,6 +334,31 @@ prompt_new_tab_name = false
     }
 
     #[test]
+    fn sidebar_bounds_default_and_parse() {
+        let default_config = Config::default();
+        assert_eq!(default_config.ui.sidebar_min_width, 18);
+        assert_eq!(default_config.ui.sidebar_max_width, 36);
+
+        let toml = r#"
+[ui]
+sidebar_min_width = 12
+sidebar_max_width = 80
+"#;
+        let config: Config = toml::from_str(toml).unwrap();
+        assert_eq!(config.ui.sidebar_min_width, 12);
+        assert_eq!(config.ui.sidebar_max_width, 80);
+    }
+
+    #[test]
+    fn validated_sidebar_bounds_rejects_inverted() {
+        assert_eq!(validated_sidebar_bounds(18, 36), Some((18, 36)));
+        assert_eq!(validated_sidebar_bounds(20, 20), Some((20, 20)));
+        assert_eq!(validated_sidebar_bounds(0, u16::MAX), Some((0, u16::MAX)));
+        assert_eq!(validated_sidebar_bounds(50, 30), None);
+        assert_eq!(validated_sidebar_bounds(u16::MAX, 0), None);
+    }
+
+    #[test]
     fn mouse_capture_default_on_and_parse() {
         let default_config = Config::default();
         assert!(default_config.ui.mouse_capture);