package redis

import (
	"hash/adler32"
	"sync"
)

// Event holds a single Redis publish message event
type Event struct {
	Chan string // Chan holds the publish channel name
	Msg  string // Msg is the published message data
}

// eventCache caches all Publish events
type eventCache struct {
	mu  sync.Mutex
	evs map[uint32]Event
}

// Add a single publish event to the cache
func (c *eventCache) Add(channel string, msg string) {
	// We hash the sum of the channel and message to save RAM and lookup time in the cache
	h := adler32.Checksum([]byte(channel + msg))

	c.mu.Lock()

	if _, ok := c.evs[h]; ok {
		c.mu.Unlock()
		return
	}

	c.evs[h] = Event{Chan: channel, Msg: msg}
	c.mu.Unlock()
}

// Flush and get all the current publish events
func (c *eventCache) Flush() []Event {
	c.mu.Lock()

	evs := make([]Event, 0, len(c.evs))

	var n = 0

	for _, e := range c.evs {
		evs = append(evs, e)
		n++
	}

	c.evs = make(map[uint32]Event)
	c.mu.Unlock()

	return evs
}