package core

import (
	"errors"
	"fmt"
)

type Subscriber interface {
	Subscribe() (int16, <-chan string)
	Unsubscribe(id int16) error
}

type Publisher interface {
	Publish(message string)
}

type dispatcher struct {
	listeners map[int16]chan string
	counter   int16
}

func NewDispatcher() *dispatcher {
	fmt.Println("new dispatcher")
	return &dispatcher{
		listeners: make(map[int16]chan string),
		counter:   0,
	}
}

func (d *dispatcher) Publish(message string) {
	//fmt.Println("publish to listeners", len(d.listeners))
	for _, ch := range d.listeners {
		ch <- message
	}
}

func (d *dispatcher) Subscribe() (id int16, receiver <-chan string) {
	fmt.Println("subscribe")
	key := d.counter
	d.counter++
	rec := make(chan string)
	d.listeners[key] = rec
	return key, rec
}

func (d *dispatcher) Unsubscribe(id int16) error {
	fmt.Println("unsubscribe")
	receiver, ok := d.listeners[id]
	if !ok {
		return errors.New("no subscription with id")
	}
	delete(d.listeners, id)
	close(receiver)
	return nil
}