package appview

import "fmt"

// themeRegistry maps theme names to their BrandingOverrides constructors.
var themeRegistry = make(map[string]func() *BrandingOverrides)

// RegisterTheme registers a named theme. Call from init() in theme packages.
func RegisterTheme(name string, fn func() *BrandingOverrides) {
	if _, exists := themeRegistry[name]; exists {
		panic(fmt.Sprintf("theme %q already registered", name))
	}
	themeRegistry[name] = fn
}

// LookupTheme returns BrandingOverrides for a registered theme name.
// Returns nil for empty name (default branding). Returns an error for
// unknown theme names.
func LookupTheme(name string) (*BrandingOverrides, error) {
	if name == "" {
		return nil, nil
	}
	fn, ok := themeRegistry[name]
	if !ok {
		return nil, fmt.Errorf("unknown theme %q", name)
	}
	return fn(), nil
}