jecs-nightly/jecs/addons/observers.luau

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local jecs = require("@jecs")
type Observer<T...> = {
callback: (jecs.Entity) -> (),
query: jecs.Query<T...>,
}
export type PatchedWorld = jecs.World & {
added: (PatchedWorld, jecs.Id, (e: jecs.Entity, id: jecs.Id, value: any) -> ()) -> (),
removed: (PatchedWorld, jecs.Id, (e: jecs.Entity, id: jecs.Id) -> ()) -> (),
changed: (PatchedWorld, jecs.Id, (e: jecs.Entity, id: jecs.Id) -> ()) -> (),
observer: (PatchedWorld, Observer<any>) -> (),
monitor: (PatchedWorld, Observer<any>) -> (),
}
local function observers_new(world, description)
local query = description.query
local callback = description.callback
local terms = query.filter_with :: { jecs.Id }
if not terms then
local ids = query.ids
query.filter_with = ids
terms = ids
end
local entity_index = world.entity_index :: any
local function emplaced(entity: jecs.Entity)
local r = jecs.entity_index_try_get_fast(
entity_index, entity :: any)
if not r then
return
end
local archetype = r.archetype
if jecs.query_match(query, archetype) then
callback(entity)
end
end
for _, term in terms do
world:added(term, emplaced)
world:changed(term, emplaced)
end
end
local function monitors_new(world, description)
local query = description.query
local callback = description.callback
local terms = query.filter_with :: { jecs.Id }
if not terms then
local ids = query.ids
query.filter_with = ids
terms = ids
end
local entity_index = world.entity_index :: any
local function emplaced(entity: jecs.Entity)
local r = jecs.entity_index_try_get_fast(
entity_index, entity :: any)
if not r then
return
end
local archetype = r.archetype
if jecs.query_match(query, archetype) then
callback(entity, jecs.OnAdd)
end
end
local function removed(entity: jecs.Entity, component: jecs.Id)
local r = jecs.entity_index_try_get_fast(
entity_index, entity :: any)
if not r then
return
end
local archetype = r.archetype
if jecs.query_match(query, archetype) then
callback(entity, jecs.OnRemove)
end
end
for _, term in terms do
world:added(term, emplaced)
world:removed(term, removed)
end
end
local function observers_add(world: jecs.World & { [string]: any }): PatchedWorld
local signals = {
added = {},
emplaced = {},
removed = {}
}
world.added = function(_, component, fn)
local listeners = signals.added[component]
if not listeners then
listeners = {}
signals.added[component] = listeners
local idr = jecs.id_record_ensure(world, component)
idr.hooks.on_add = function(entity)
for _, listener in listeners do
listener(entity, component)
end
end
end
table.insert(listeners, fn)
end
world.changed = function(_, component, fn)
local listeners = signals.emplaced[component]
if not listeners then
listeners = {}
signals.emplaced[component] = listeners
local idr = jecs.id_record_ensure(world, component)
idr.hooks.on_change = function(entity, value)
for _, listener in listeners do
listener(entity, component, value)
end
end
end
table.insert(listeners, fn)
end
world.removed = function(_, component, fn)
local listeners = signals.removed[component]
if not listeners then
listeners = {}
signals.removed[component] = listeners
local idr = jecs.id_record_ensure(world, component)
idr.hooks.on_remove = function(entity)
for _, listener in listeners do
listener(entity, component)
end
end
end
table.insert(listeners, fn)
end
world.signals = signals
world.observer = observers_new
world.monitor = monitors_new
return world
end
return observers_add