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group.go
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group.go
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package entitas
type Group interface {
Entities() []Entity
HandleEntity(e Entity)
UpdateEntity(e Entity)
WillRemoveEntity(e Entity)
Matches(e Entity) bool
ContainsEntity(e Entity) bool
AddCallback(e GroupEvent, c GroupCallback)
}
type GroupEvent uint
const (
EntityAdded GroupEvent = iota
EntityWillBeRemoved
EntityRemoved
)
type GroupCallback func(Group, Entity)
type group struct {
entities map[EntityID]Entity
cache []Entity
cacheInvalidated bool
matcher Matcher
callbacks map[GroupEvent][]GroupCallback
}
func NewGroup(matcher Matcher) Group {
return &group{
entities: make(map[EntityID]Entity),
cache: make([]Entity, 0),
cacheInvalidated: false,
matcher: matcher,
callbacks: make(map[GroupEvent][]GroupCallback),
}
}
func (g *group) Entities() []Entity {
if g.cacheInvalidated {
cache := make([]Entity, len(g.entities))
i := 0
for _, e := range g.entities {
cache[i] = e
i++
}
g.cache = cache
g.cacheInvalidated = false
}
return g.cache
}
func (g *group) HandleEntity(e Entity) {
if g.matcher.Matches(e) {
g.addEntity(e)
} else {
g.removeEntity(e)
}
}
func (g *group) UpdateEntity(e Entity) {
if _, ok := g.entities[e.ID()]; ok {
g.callback(EntityRemoved, e)
g.callback(EntityAdded, e)
}
}
func (g *group) WillRemoveEntity(e Entity) {
if _, ok := g.entities[e.ID()]; ok {
g.callback(EntityWillBeRemoved, e)
}
}
func (g *group) Matches(e Entity) bool {
return g.matcher.Matches(e)
}
func (g *group) ContainsEntity(e Entity) bool {
if _, ok := g.entities[e.ID()]; ok {
return true
}
return false
}
func (g *group) AddCallback(ev GroupEvent, c GroupCallback) {
cs, ok := g.callbacks[ev]
if !ok {
cs = make([]GroupCallback, 0)
}
g.callbacks[ev] = append(cs, c)
}
func (g *group) addEntity(e Entity) {
if _, ok := g.entities[e.ID()]; !ok {
g.entities[e.ID()] = e
if g.cacheInvalidated == false {
g.cache = append(g.cache, e)
}
g.callback(EntityAdded, e)
}
}
func (g *group) removeEntity(e Entity) {
if _, ok := g.entities[e.ID()]; ok {
delete(g.entities, e.ID())
if i := findIndex(g.cache, e); i != -1 {
g.cache = nil
g.cacheInvalidated = true
}
g.callback(EntityRemoved, e)
}
}
func (g *group) callback(ev GroupEvent, e Entity) {
if cs, ok := g.callbacks[ev]; ok {
for _, c := range cs {
c(g, e)
}
}
}
func findIndex(entities []Entity, e Entity) int {
for i, entity := range entities {
if entity == e {
return i
}
}
return -1
}
func removeIndexed(entities []Entity, i int) []Entity {
copy(entities[i:], entities[i+1:])
entities[len(entities)-1] = nil
new := entities[:len(entities)-1]
return new
}