fix: move original starship config to backup if existent

Author: a3chron

README.md

@@ -61,9 +61,24 @@ stellar update
 
 ## Local configs
 
+### Automatic backup of your original config
+
+When you first use `stellar apply`, if you have an existing `~/.config/starship.toml` that's not managed by stellar, it will be automatically backed up to `~/.config/stellar/<username>/backup/latest.toml` before creating the symlink.
+
+This ensures your carefully crafted config is never lost! You can apply it anytime with:
+```bash
+stellar apply <username>/backup
+```
+
+You can also rename the backup folder to give it a proper theme name:
+```bash
+mv ~/.config/stellar/<username>/backup ~/.config/stellar/<username>/my-custom-theme
+stellar apply <username>/my-custom-theme
+```
+
 ### Switching between local configs
 
-You can just put your own configs under `~/.config/stellar/local/<your-theme>/latest.toml`, 
+You can just put your own configs under `~/.config/stellar/local/<your-theme>/latest.toml`,
 and then switch to them using `stellar apply local/<your-theme>`.
 
 > [!INFO]
@@ -72,7 +87,7 @@ and then switch to them using `stellar apply local/<your-theme>`.
 
 ### Customizing themes
 
-You can similarily copy one existing downloaded theme to the `stellar/local` folder, edit it, 
+You can similarily copy one existing downloaded theme to the `stellar/local` folder, edit it,
 and then switch to it using `stellar apply`.
 
 > [!INFO]

cmd/apply.go

@@ -3,6 +3,7 @@ package cmd
 import (
 	"fmt"
 	"log"
+	"os/user"
 
 	"github.com/a3chron/stellar/internal/api"
 	"github.com/a3chron/stellar/internal/cache"
@@ -13,6 +14,14 @@ import (
 	"github.com/spf13/cobra"
 )
 
+func getCurrentUsername() string {
+	currentUser, err := user.Current()
+	if err != nil {
+		return "local"
+	}
+	return currentUser.Username
+}
+
 var applyCmd = &cobra.Command{
 	Use:   "apply [author/theme[@version]]",
 	Short: "Apply a Starship theme",
@@ -85,10 +94,18 @@ var applyCmd = &cobra.Command{
 		}
 
 		// 6. Create symlink
-		if err := symlink.CreateSymlink(themePath); err != nil {
+		backupPath, err := symlink.CreateSymlink(themePath)
+		if err != nil {
 			return err
 		}
 
+		// Notify user if their original config was backed up
+		if backupPath != "" {
+			color.Yellow("Your original starship.toml has been backed up to:")
+			color.Yellow("  %s", backupPath)
+			color.Cyan("\nYou can apply it later with: stellar apply %s/backup \n", getCurrentUsername())
+		}
+
 		color.Green("Applied %s", t)
 		return nil
 	},

cmd/rollback.go

@@ -75,7 +75,8 @@ var rollbackCmd = &cobra.Command{
 		}
 
 		// Update symlink
-		if err := symlink.CreateSymlink(cfg.CurrentPath); err != nil {
+		_, err = symlink.CreateSymlink(cfg.CurrentPath)
+		if err != nil {
 			return fmt.Errorf("failed to update symlink: %w", err)
 		}
 

internal/symlink/symlink.go

@@ -1,8 +1,11 @@
 package symlink
 
 import (
+	"fmt"
+	"io"
 	"log"
 	"os"
+	"os/user"
 	"path/filepath"
 )
 
@@ -14,19 +17,101 @@ func StarshipConfigPath() (string, error) {
 	return filepath.Join(home, ".config", "starship.toml"), nil
 }
 
-func CreateSymlink(target string) error {
+// isSymlink checks if the given path is a symlink
+func isSymlink(path string) bool {
+	info, err := os.Lstat(path)
+	if err != nil {
+		return false
+	}
+	return info.Mode()&os.ModeSymlink != 0
+}
+
+// backupOriginalConfig backs up the user's original starship.toml to ~/.config/stellar/<username>/backup/latest.toml
+// Returns the backup path if successful, empty string otherwise
+func backupOriginalConfig(configPath string) (backupPath string, err error) {
+	// Check if the file exists and is NOT a symlink
+	if _, err := os.Stat(configPath); os.IsNotExist(err) {
+		return "", nil // No file to back up
+	}
+
+	if isSymlink(configPath) {
+		return "", nil // Already a symlink, no need to back up
+	}
+
+	// Get the current user's username
+	currentUser, err := user.Current()
+	if err != nil {
+		return "", fmt.Errorf("failed to get current user: %w", err)
+	}
+
+	// Construct backup path: ~/.config/stellar/<username>/backup/latest.toml
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("failed to get home directory: %w", err)
+	}
+
+	backupDir := filepath.Join(home, ".config", "stellar", currentUser.Username, "backup")
+	backupPath = filepath.Join(backupDir, "latest.toml")
+
+	// Create backup directory
+	if err := os.MkdirAll(backupDir, 0755); err != nil {
+		return "", fmt.Errorf("failed to create backup directory: %w", err)
+	}
+
+	// Copy the original file to backup location
+	source, err := os.Open(configPath)
+	if err != nil {
+		return "", fmt.Errorf("failed to open original config: %w", err)
+	}
+	defer func() {
+		if cerr := source.Close(); cerr != nil && err == nil {
+			err = fmt.Errorf("failed to close source file: %w", cerr)
+		}
+	}()
+
+	destination, err := os.Create(backupPath)
+	if err != nil {
+		return "", fmt.Errorf("failed to create backup file: %w", err)
+	}
+	defer func() {
+		if cerr := destination.Close(); cerr != nil && err == nil {
+			err = fmt.Errorf("failed to close destination file: %w", cerr)
+		}
+	}()
+
+	if _, err := io.Copy(destination, source); err != nil {
+		return "", fmt.Errorf("failed to copy config to backup: %w", err)
+	}
+
+	return backupPath, nil
+}
+
+// CreateSymlink creates a symlink from ~/.config/starship.toml to the target file.
+// If an original (non-symlink) starship.toml exists, it's backed up first.
+// Returns the backup path if a backup was created (empty string if no backup was needed).
+func CreateSymlink(target string) (backupPath string, err error) {
 	configPath, err := StarshipConfigPath()
 	if err != nil {
-		return err
+		return "", err
+	}
+
+	// Back up original config if it exists and is not a symlink
+	backupPath, err = backupOriginalConfig(configPath)
+	if err != nil {
+		return "", fmt.Errorf("failed to backup original config: %w", err)
 	}
 
 	// Remove existing symlink/file
-	if err := os.Remove(configPath); err != nil {
+	if err := os.Remove(configPath); err != nil && !os.IsNotExist(err) {
 		log.Printf("warning: failed to remove %s: %v", configPath, err)
 	}
 
 	// Create new symlink
-	return os.Symlink(target, configPath)
+	if err := os.Symlink(target, configPath); err != nil {
+		return backupPath, err
+	}
+
+	return backupPath, nil
 }
 
 func GetCurrentTarget() (string, error) {