feat(go): implement unlink

internal/homesick/core/core.go

@@ -173,8 +173,44 @@ func (a *App) LinkCastle(castle string) error {
 	return nil
 }
 
-func (a *App) Unlink(string) error {
-	return errors.New("unlink is not implemented in Go yet")
+func (a *App) Unlink(castle string) error {
+	if strings.TrimSpace(castle) == "" {
+		castle = "dotfiles"
+	}
+	return a.UnlinkCastle(castle)
+}
+
+func (a *App) UnlinkCastle(castle string) error {
+	castleHome := filepath.Join(a.ReposDir, castle, "home")
+	info, err := os.Stat(castleHome)
+	if err != nil || !info.IsDir() {
+		return fmt.Errorf("could not symlink %s, expected %s to exist and contain dotfiles", castle, castleHome)
+	}
+
+	subdirs, err := readSubdirs(filepath.Join(a.ReposDir, castle, ".homesick_subdir"))
+	if err != nil {
+		return err
+	}
+
+	if err := a.unlinkEach(castleHome, castleHome, subdirs); err != nil {
+		return err
+	}
+
+	for _, subdir := range subdirs {
+		base := filepath.Join(castleHome, subdir)
+		if _, err := os.Stat(base); err != nil {
+			if errors.Is(err, os.ErrNotExist) {
+				continue
+			}
+			return err
+		}
+
+		if err := a.unlinkEach(castleHome, base, subdirs); err != nil {
+			return err
+		}
+	}
+
+	return nil
 }
 
 func (a *App) Track(string, string) error {
@@ -220,6 +256,61 @@ func (a *App) linkEach(castleHome string, baseDir string, subdirs []string) erro
 	return nil
 }
 
+func (a *App) unlinkEach(castleHome string, baseDir string, subdirs []string) error {
+	entries, err := os.ReadDir(baseDir)
+	if err != nil {
+		return err
+	}
+
+	for _, entry := range entries {
+		name := entry.Name()
+		if name == "." || name == ".." {
+			continue
+		}
+
+		source := filepath.Join(baseDir, name)
+		ignore, err := matchesIgnoredDir(castleHome, source, subdirs)
+		if err != nil {
+			return err
+		}
+		if ignore {
+			continue
+		}
+
+		relDir, err := filepath.Rel(castleHome, baseDir)
+		if err != nil {
+			return err
+		}
+
+		destination := filepath.Join(a.HomeDir, relDir, name)
+		if relDir == "." {
+			destination = filepath.Join(a.HomeDir, name)
+		}
+
+		if err := unlinkPath(destination); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func unlinkPath(destination string) error {
+	info, err := os.Lstat(destination)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil
+		}
+		return err
+	}
+
+	if info.Mode()&os.ModeSymlink == 0 {
+		return nil
+	}
+
+	return os.Remove(destination)
+}
+
 func (a *App) linkPath(source string, destination string) error {
 	absSource, err := filepath.Abs(source)
 	if err != nil {