package pushprocessor

import (
	"fmt"
	"sync"
)

// Registry manages push notification handlers.
type Registry struct {
	mu        sync.RWMutex
	handlers  map[string]Handler
	protected map[string]bool
}

// NewRegistry creates a new push notification registry.
func NewRegistry() *Registry {
	return &Registry{
		handlers:  make(map[string]Handler),
		protected: make(map[string]bool),
	}
}

// RegisterHandler registers a handler for a specific push notification name.
// Returns an error if a handler is already registered for this push notification name.
// If protected is true, the handler cannot be unregistered.
func (r *Registry) RegisterHandler(pushNotificationName string, handler Handler, protected bool) error {
	r.mu.Lock()
	defer r.mu.Unlock()

	if _, exists := r.handlers[pushNotificationName]; exists {
		return fmt.Errorf("handler already registered for push notification: %s", pushNotificationName)
	}

	r.handlers[pushNotificationName] = handler
	r.protected[pushNotificationName] = protected
	return nil
}

// UnregisterHandler removes a handler for a specific push notification name.
// Returns an error if the handler is protected or doesn't exist.
func (r *Registry) UnregisterHandler(pushNotificationName string) error {
	r.mu.Lock()
	defer r.mu.Unlock()

	_, exists := r.handlers[pushNotificationName]
	if !exists {
		return fmt.Errorf("no handler registered for push notification: %s", pushNotificationName)
	}

	if r.protected[pushNotificationName] {
		return fmt.Errorf("cannot unregister protected handler for push notification: %s", pushNotificationName)
	}

	delete(r.handlers, pushNotificationName)
	delete(r.protected, pushNotificationName)
	return nil
}

// GetHandler returns the handler for a specific push notification name.
// Returns nil if no handler is registered for the given name.
func (r *Registry) GetHandler(pushNotificationName string) Handler {
	r.mu.RLock()
	defer r.mu.RUnlock()

	handler, exists := r.handlers[pushNotificationName]
	if !exists {
		return nil
	}
	return handler
}

// GetRegisteredPushNotificationNames returns a list of all registered push notification names.
func (r *Registry) GetRegisteredPushNotificationNames() []string {
	r.mu.RLock()
	defer r.mu.RUnlock()

	names := make([]string, 0, len(r.handlers))
	for name := range r.handlers {
		names = append(names, name)
	}
	return names
}