feat(theming): apply writes four tool configs to $HOME

internal/theming/theming.go

@@ -7,9 +7,13 @@ import (
 	"embed"
 	"fmt"
 	"io/fs"
+	"os"
 	"path/filepath"
 	"sort"
+	"strings"
 
+	"github.com/MDietermann/ArduinoArchSetup/internal/config"
+	"github.com/MDietermann/ArduinoArchSetup/internal/platform"
 	"gopkg.in/yaml.v3"
 )
 
@@ -95,3 +99,47 @@ func Get(id string) (Theme, bool) {
 	}
 	return Theme{}, false
 }
+
+// toolConfig describes one tool's config file: its asset name under
+// assets/<theme>/ and its user-config destination relative to $HOME.
+type toolConfig struct {
+	Asset   string // e.g. "starship.toml"
+	DestRel string // e.g. ".config/starship.toml"
+}
+
+var toolConfigs = []toolConfig{
+	{"starship.toml", ".config/starship.toml"},
+	{"zellij.kdl", ".config/zellij/config.kdl"},
+	{"yazi.toml", ".config/yazi/theme.toml"},
+	{"lazygit.yml", ".config/lazygit/config.yml"},
+}
+
+// Apply writes each tool's theme config to the user's home directory.
+// Task 3 adds overlay-file update; Task 4 adds NvChad chadrc rewrite.
+func Apply(cfg config.Config, themeID string) error {
+	th, ok := Get(themeID)
+	if !ok {
+		ids := make([]string, 0, len(discovered))
+		for _, t := range discovered {
+			ids = append(ids, t.ID)
+		}
+		return fmt.Errorf("unknown theme %q; valid: %s", themeID, strings.Join(ids, ", "))
+	}
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return err
+	}
+
+	for _, tc := range toolConfigs {
+		data, err := assetsFS.ReadFile(filepath.Join("assets", th.ID, tc.Asset))
+		if err != nil {
+			return fmt.Errorf("read asset %s: %w", tc.Asset, err)
+		}
+		dst := filepath.Join(home, tc.DestRel)
+		if err := platform.WriteUserFile(dst, data, 0o644); err != nil {
+			return fmt.Errorf("write %s: %w", tc.DestRel, err)
+		}
+	}
+	_ = cfg // overlay update lands in Task 3
+	return nil
+}