package serverevents

import (
	"fmt"
	di "git.apihub24.de/admin/generic-di"
	"sync"
)

func init() {
	di.Injectable(newEventHandlerRegistration)
}

type IEventHandlerRegistration interface {
	Add(eventType string, creator func() IEventHandler)
	GetHandler(eventType string) (IEventHandler, error)
}

type eventHandlerRegistration struct {
	creators  map[string]func() IEventHandler
	instances map[string]IEventHandler
	mutex     sync.RWMutex
}

func newEventHandlerRegistration() IEventHandlerRegistration {
	return &eventHandlerRegistration{
		creators:  make(map[string]func() IEventHandler),
		instances: make(map[string]IEventHandler),
		mutex:     sync.RWMutex{},
	}
}

func (registration *eventHandlerRegistration) Add(eventType string, creator func() IEventHandler) {
	registration.mutex.Lock()
	defer registration.mutex.Unlock()

	if _, ok := registration.instances[eventType]; ok {
		delete(registration.instances, eventType)
	}
	if _, ok := registration.creators[eventType]; ok {
		delete(registration.creators, eventType)
	}
	registration.creators[eventType] = creator
}

func (registration *eventHandlerRegistration) GetHandler(eventType string) (IEventHandler, error) {
	registration.mutex.RLock()
	defer registration.mutex.RUnlock()

	if creator, ok := registration.creators[eventType]; ok {
		if instance, ok := registration.instances[eventType]; ok {
			return instance, nil
		}
		registration.instances[eventType] = creator()
		return registration.instances[eventType], nil
	}
	return nil, fmt.Errorf("no instance of IEventHandler registered for Event %s! please call Registration Add in a init function to register your EventHandler", eventType)
}