FollowCD · June 17, 2019 10:00 · Jun 17, 2019 · Jun 17, 2019
diff --git a/test.lua b/test.lua
@@ -0,0 +1,38 @@
+
+
+local World = require("ecs").World
+
+local w = World:new()
+
+w:register_components({
+    transform = 0,
+    rotation = 1
+})
+
+local e1 = w:new_entity()
+local e2 = w:new_entity()
+
+e1:add_component("transform", {x = 0, y = 0, z = 9})
+
+e2:add_component("transform", {x = 0, y = 0, z = 9})
+e2:add_component("rotation", {angle = 0})
+
+function tick(entities, dT)
+    for i, e in ipairs(entities) do
+        e.transform.x = e.transform.x + dT
+    end
+end
+
+local s = {
+    tick = tick,
+    components = {"transform", "rotation"}
+}
+
+w:add_system(s)
+
+w:tick(0.5)
+print(e1.transform.x)
+print(e2.transform.x)
+w:tick(0.56)
+print(e1.transform.x)
+print(e2.transform.x)
diff --git a/ecs.lua b/ecs.lua
@@ -0,0 +1,114 @@
+local Entity = {
+}
+local EntityMeta = {
+    __index = function(entity, key)
+        local o = rawget(Entity, key)
+        if(o ~= nil) then
+            return o
+        end
+        local component_id = key
+        if(type(component_id) == "string") then
+            component_id = entity:lookup_component_id(key)
+            if(component_id == nil) then
+                return nil
+            end
+        end
+        local component_index = entity.component_indices[component_id]
+        if(component_index ~= nil) then
+            local components = entity.world.components[component_id]
+            if(components ~= nil) then
+                return components[component_index]
+            end
+        end
+        return nil
+    end
+}
+
+function Entity:new(world)
+    local o = {}
+    o.world = world
+    o.component_indices = {}
+    setmetatable(o, EntityMeta)
+    return o
+end
+
+function Entity:add_component(key, c)
+    local component_id = key
+    if(type(component_id) == "string") then
+        component_id = self:lookup_component_id(component_id)
+    end
+    if(component_id == nil) then
+        return
+    end
+    local world = self.world
+    local components = world.components[component_id]
+    if(components == nil) then
+        components = {}
+        world.components[component_id] = components
+    end
+    table.insert(components, c)
+    local idx = #components
+    self.component_indices[component_id] = idx
+    self.mask = self.mask or 0
+    self.mask = self.mask | (1 << component_id)
+end
+
+function Entity:lookup_component_id(name)
+    return self.world.component_map[name]
+end
+
+local World = {
+}
+
+function World:new(o)
+    local o = o or {
+        entities = {},
+        components = {},
+        systems = {},
+        component_map = {}
+    }
+    setmetatable(o, {__index = World})
+    return o
+end
+
+function World:new_entity()
+    local e = Entity:new(self)
+    table.insert(self.entities, e)
+    return e
+end
+
+function World:add_system(s)
+    table.insert(self.systems, s)
+    s.mask = self:generate_mask(s.components)
+end
+
+function World:register_components(m)
+    self.component_map = m
+end
+
+function World:generate_mask(components)
+    local mask = 0
+    for i, v in ipairs(components) do
+        local component_id = self.component_map[v]
+        if(component_id ~= nil) then
+            mask = mask | (1 << component_id)
+        end
+    end
+    return mask
+end
+
+function World:tick(dT)
+    for system_idx, system in ipairs(self.systems) do
+        local entities = {}
+        for entity_idx, entity in ipairs(self.entities) do
+            if(system.mask & ~entity.mask == 0) then
+                table.insert(entities, entity)
+            end
+        end
+        system.tick(entities, dT)
+    end
+end
+
+return {
+    World = World
+}