package buildrun

import (
	"sync"

	"git.novox.be/novox/mesh-sdk/go/delivery"
)

// PresenceSet holds which nodes are online, as the watchman writes it (mesh-delivery-watchman_presence, key `<node>`, the
// node-engine's connection): a node asleep or off the bus is offline and its build module cannot answer. A node the
// watchman has no key of is not online. Safe for use from the watch and from a build at once.
type PresenceSet struct {
	mu     sync.Mutex
	online map[string]bool
}

// Put takes a change of the presence bucket in and answers whether a node's online state changed. A part's key and a
// value that is not a presence are left out.
func (s *PresenceSet) Put(key string, value []byte, deleted bool) bool {
	node, part, _, err := delivery.ParsePresenceKey(key)
	if err != nil || part != "" {
		return false
	}
	on := false
	if !deleted {
		p, err := delivery.DecodePresence(value)
		if err != nil {
			return false
		}
		on = p.Online
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.online[node] == on {
		return false
	}
	if s.online == nil {
		s.online = map[string]bool{}
	}
	if on {
		s.online[node] = true
	} else {
		delete(s.online, node)
	}
	return true
}

// Online is whether the watchman last saw the node online.
func (s *PresenceSet) Online(node string) bool {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.online[node]
}