package database

import (

"context"

"sync"

"github.com/google/uuid"

)

// memoryPubsub is an in-memory Pubsub implementation.

type memoryPubsub struct {

mut sync.RWMutex

listeners map[string]map[uuid.UUID]Listener

}

func (m *memoryPubsub) Subscribe(event string, listener Listener) (cancel func(), err error) {

m.mut.Lock()

defer m.mut.Unlock()

var listeners map[uuid.UUID]Listener

var ok bool

if listeners, ok = m.listeners[event]; !ok {

listeners = map[uuid.UUID]Listener{}

m.listeners[event] = listeners

}

var id uuid.UUID

for {

id = uuid.New()

if _, ok = listeners[id]; !ok {

break

}

}

listeners[id] = listener

return func() {

m.mut.Lock()

defer m.mut.Unlock()

listeners := m.listeners[event]

delete(listeners, id)

}, nil

}

func (m *memoryPubsub) Publish(event string, message []byte) error {

m.mut.RLock()

defer m.mut.RUnlock()

listeners, ok := m.listeners[event]

if !ok {

return nil

}

for _, listener := range listeners {

go listener(context.Background(), message)

}

return nil

}

func (*memoryPubsub) Close() error {

return nil

}

func NewPubsubInMemory() Pubsub {

return &memoryPubsub{

listeners: make(map[string]map[uuid.UUID]Listener),

}

}