package events

import (
	"sync"
)

// ClientMessage represents a message sent by the client
type ClientMessage struct {
	Type    string `json:"type"`
	Message string `json:"message"`
}

// ServerEvent represents an event sent to the client
type ServerEvent struct {
	Type string      `json:"type"`
	Data interface{} `json:"message"`
}

// Eventer define an interface that any eventer must follow
type Eventer interface {
	Subscribe(func())
	Unsubscribe()
	Launch()
}

// Notifier represents the base of any Eventer
// Notify implements Subscribe and Unsubscribe methods
type Notifier struct {
	sync.RWMutex
	subscribed  bool
	done        chan struct{}
	eventStream chan ServerEvent
}

// NewNotifier returns a new notifier
func NewNotifier(eventStream chan ServerEvent) *Notifier {
	return &Notifier{
		eventStream: eventStream,
		done:        make(chan struct{}),
	}
}

// Subscribe subscribes a client on the Notifier
func (t *Notifier) Subscribe(launch func()) {
	t.Lock()
	defer t.Unlock()

	// Check if already subscribed
	if t.subscribed {
		return
	}
	t.subscribed = true

	go launch()
}

// Unsubscribe unsubscribes a client from receiving any more events from
// the Notifier
func (t *Notifier) Unsubscribe() {
	t.Lock()
	defer t.Unlock()

	// Check if already unsubscribed
	if !t.subscribed {
		return
	}
	t.subscribed = false

	t.done <- struct{}{}
}