package main

import (
	"fmt"
	"log"
)

type States map[string]bool

type Cache struct {
	Tx     chan MQTTMessage
	States map[string]bool
}

func NewCache(tx chan MQTTMessage) Cache {
	var cache Cache

	cache.Tx     = tx
	cache.States = make(States)

	return cache
}

func (c *Cache) Update(states States) {
	if c.States == nil {
		log.Fatal("Cache states is nil.")
	}

	if states == nil {
		log.Fatal("Given states is nil.")
	}

	for id, state := range states {
		cached, known := c.States[id]
		if !known || cached != state {
			topic := fmt.Sprintf("contact/%s/state", id)
			var payload []byte
			if state == true {
				payload = []byte("open")
			} else {
				payload = []byte("closed")
			}
			c.Tx <- MQTTMessage{
				Topic: topic,
				Payload: payload,
			}
		}
		c.States[id] = state
	}
}