1 files changed, 96 insertions, 1 deletions
diff --git a/honey/ecs.lua b/honey/ecs.lua
index ef682b5..3bdf850 100644
--- a/honey/ecs.lua
+++ b/honey/ecs.lua
@@ -23,7 +23,8 @@ function Filter.new(_, operation, tbl)
 		end
 	end
 
-	return function(entity) 
+	return function(entity, _self) 
+		local entity = _self or entity -- able to call as . or :
 		return Filter.check(self, entity)
 	end
 end
@@ -97,4 +98,98 @@ function Filter.checkNOR(self, entity)
 end
 
 
+--===== worlds =====--
+
+World = {}
+World.__index = World
+
+function World.new(_)
+	local self = {}
+	self.systems = {}
+	self.entities = {}
+	setmetatable(self, World)
+	return self
+end
+setmetatable(World, {__call=World.new})
+
+
+local function systemLt(a, b)
+	return (a.priority or 50) < (b.priority or 50)
+end
+function World.addSystem(self, system)
+	assert(system.update, "systems must have an 'update' key")
+	assert(system.filter, "systems must have a 'filter' key")
+	system.entities = {}
+	table.insert(self.systems, system)
+	table.sort(self.systems, systemLt)
+end
+
+
+local function addEntityToSystem(system, entity)
+	-- check if entity is already present
+	if system.entities[entity] then return end
+
+	if system.onAddEntity then
+		system.onAddEntity(entity)
+	end
+	system.entities[entity] = true
+end
+
+
+local function removeEntityFromSystem(system, entity)
+	-- check if entity is already absent
+	if not system.entities[entity] then return end
+
+	if system.onRemoveEntity then
+		system.onRemoveEntity(entity)
+	end
+	system.entities[entity] = nil
+end
+
+
+function World.addEntity(self, entity)
+	self.entities[entity] = true
+	for _, system in ipairs(self.systems) do
+		if system.filter(entity) then
+			addEntityToSystem(system, entity)
+		end
+	end
+end
+
+
+function World.reconfigureEntity(self, entity)
+	for _, system in ipairs(self.systems) do
+		if system.filter(entity) then
+			addEntityToSystem(system, entity)
+		else
+			removeEntityFromSystem(system, entity)
+		end
+	end
+end
+
+
+function World.removeEntity(self, entity)
+	self.entities[entity] = nil
+	for _, system in ipairs(self.systems) do
+		removeEntityFromSystem(system, entity)
+	end
+end
+
+
+function World.reconfigureAllEntities(self)
+	for entity in pairs(self.entities) do
+		self:reconfigureEntity(entity)
+	end
+end
+
+
+function World.update(self, dt)
+	for _, system in ipairs(self.systems) do
+		for entity in pairs(system.entities) do
+			system.update(entity, dt)
+		end
+	end
+end
+
+
 return module