package serverevents

import (
	di "git.apihub24.de/admin/generic-di"
	"github.com/google/uuid"
	"slices"
	"sync"
)

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

type IEventEmitter interface {
	On(eventType string, do func(Event)) Subscription
	OnAll(do func(Event)) Subscription
	Emit(event Event)
	Unsubscribe(Subscription)
}

type eventEmitter struct {
	subscribers      map[string][]Subscription
	onAllSubscribers []Subscription
	mu               sync.RWMutex
}

func newEventEmitter() IEventEmitter {
	return &eventEmitter{}
}

func (emitter *eventEmitter) On(eventType string, do func(Event)) Subscription {
	emitter.mu.Lock()
	defer emitter.mu.Unlock()

	if emitter.subscribers[eventType] == nil {
		emitter.subscribers[eventType] = make([]Subscription, 0)
	}
	sub := Subscription{
		id:        uuid.NewString(),
		eventType: eventType,
		todo:      do,
		emitter:   emitter,
	}
	emitter.subscribers[eventType] = append(emitter.subscribers[eventType], sub)
	return sub
}

func (emitter *eventEmitter) OnAll(do func(Event)) Subscription {
	emitter.mu.Lock()
	defer emitter.mu.Unlock()

	sub := Subscription{
		id:      uuid.NewString(),
		todo:    do,
		emitter: emitter,
	}
	emitter.onAllSubscribers = append(emitter.onAllSubscribers, sub)
	return sub
}

func (emitter *eventEmitter) Emit(event Event) {
	emitter.executeSubscribers(emitter.onAllSubscribers, event)
	eventSubscribers := emitter.subscribers[event.Type]
	if eventSubscribers != nil {
		emitter.executeSubscribers(eventSubscribers, event)
	}
}

func (emitter *eventEmitter) Unsubscribe(subscription Subscription) {
	if len(subscription.eventType) < 1 {
		emitter.onAllSubscribers = slices.DeleteFunc(emitter.onAllSubscribers, func(existSub Subscription) bool {
			return existSub.id == subscription.id
		})
		return
	}
	eventSubscribers := emitter.subscribers[subscription.eventType]
	if eventSubscribers == nil || len(eventSubscribers) < 1 {
		return
	}
	emitter.subscribers[subscription.eventType] = slices.DeleteFunc(emitter.subscribers[subscription.eventType], func(existSub Subscription) bool {
		return existSub.id == subscription.id
	})
}

func (emitter *eventEmitter) executeSubscribers(toDos []Subscription, event Event) {
	for _, sub := range toDos {
		sub.todo(event)
	}
}