Added base theme for defaults

src/apply.rs

@@ -103,13 +103,33 @@ pub fn plan_apply(
     force: bool,
     current_state: Option<&State>,
 ) -> Result<ApplyPlan> {
-    let theme_dir = themes_root()?.join(theme_name);
+    if theme_name == "base" {
+        anyhow::bail!("\"base\" is a reserved layer name and cannot be applied as a theme");
+    }
+
+    let root = themes_root()?;
+    let theme_dir = root.join(theme_name);
     if !theme_dir.is_dir() {
         anyhow::bail!("theme not found: {}", theme_name);
     }
 
     let home = effective_home()?;
-    let files = enumerate_theme_files(&theme_dir)?;
+
+    // Build a merged file map: base files first, theme files overlay (and win on conflict).
+    // Using BTreeMap keeps the iteration order deterministic.
+    let mut file_map: std::collections::BTreeMap<PathBuf, PathBuf> =
+        std::collections::BTreeMap::new();
+
+    let base_dir = root.join("base");
+    if base_dir.is_dir() {
+        for (rel, src) in enumerate_theme_files(&base_dir)? {
+            file_map.insert(rel, src);
+        }
+    }
+
+    for (rel, src) in enumerate_theme_files(&theme_dir)? {
+        file_map.insert(rel, src);
+    }
 
     let managed_targets: HashSet<PathBuf> = current_state
         .map(|s| s.entries.iter().map(|e| PathBuf::from(&e.target)).collect())
@@ -117,7 +137,7 @@ pub fn plan_apply(
 
     let mut actions = Vec::new();
 
-    for (relative, source) in files {
+    for (relative, source) in file_map {
         let target = home.join(&relative);
 
         match target.symlink_metadata() {
@@ -724,4 +744,78 @@ mod tests {
         let link = fs::read_link(env.home.path().join(".zshrc")).unwrap();
         assert!(link.to_string_lossy().contains("catppuccin"));
     }
+
+    // ---- base layer tests -----------------------------------------------
+
+    fn make_base_file(env: &TestEnv, rel: &str, content: &str) -> PathBuf {
+        make_theme_file(env, "base", rel, content)
+    }
+
+    #[test]
+    fn base_files_applied_alongside_theme() {
+        let env = TestEnv::new();
+        make_base_file(&env, ".config/hypr/keybinds.conf", "# base keybinds");
+        make_theme_file(&env, "dracula", ".zshrc", "# dracula");
+
+        let plan = plan_apply("dracula", false, None).unwrap();
+        assert_eq!(plan.actions.len(), 2);
+
+        let (_, summary) = execute_apply(&plan, false).unwrap();
+        assert_eq!(summary.created, 2);
+
+        let keybinds = fs::read_link(env.home.path().join(".config/hypr/keybinds.conf")).unwrap();
+        assert!(keybinds.to_string_lossy().contains("base"));
+
+        let zshrc = fs::read_link(env.home.path().join(".zshrc")).unwrap();
+        assert!(zshrc.to_string_lossy().contains("dracula"));
+    }
+
+    #[test]
+    fn theme_overrides_base_file() {
+        let env = TestEnv::new();
+        make_base_file(&env, ".zshrc", "# base zshrc");
+        make_theme_file(&env, "dracula", ".zshrc", "# dracula zshrc");
+
+        let plan = plan_apply("dracula", false, None).unwrap();
+        // Only one action — theme wins over base for same path.
+        assert_eq!(plan.actions.len(), 1);
+
+        execute_apply(&plan, false).unwrap();
+        let link = fs::read_link(env.home.path().join(".zshrc")).unwrap();
+        assert!(link.to_string_lossy().contains("dracula"));
+    }
+
+    #[test]
+    fn base_file_stays_when_theme_has_no_override() {
+        let env = TestEnv::new();
+        make_base_file(&env, ".config/hypr/keybinds.conf", "# base keybinds");
+        make_theme_file(&env, "dracula", ".zshrc", "# dracula");
+        make_theme_file(&env, "catppuccin", ".zshrc", "# catppuccin");
+
+        // Apply dracula
+        let plan = plan_apply("dracula", false, None).unwrap();
+        let (dracula_state, _) = execute_apply(&plan, false).unwrap();
+
+        // Switch to catppuccin — neither theme has keybinds.conf, so base symlink stays
+        let plan2 = plan_apply("catppuccin", false, Some(&dracula_state)).unwrap();
+
+        let keybinds_action = plan2
+            .actions
+            .iter()
+            .find(|a| match a {
+                PlannedAction::Skip { target, .. } => {
+                    target.to_string_lossy().contains("keybinds")
+                }
+                _ => false,
+            });
+        assert!(keybinds_action.is_some(), "keybinds.conf should be skipped (already correct)");
+    }
+
+    #[test]
+    fn base_is_rejected_as_theme_name() {
+        let env = TestEnv::new();
+        make_base_file(&env, ".zshrc", "# base");
+        let result = plan_apply("base", false, None);
+        assert!(result.is_err());
+    }
 }