Initial push

lib/command_buffer.luau

@@ -0,0 +1,114 @@
+--!strict
+--!optimize 2
+local jecs = require("@pkg/jecs")
+type entity<T = nil> = jecs.Entity<T>
+type id<T = nil> = jecs.Id<T>
+
+local world = require("./world").get()
+
+--- `map<component_id, array<entity_id>>`
+local add_commands: { [id]: { entity } } = {}
+--- `map<component_id, array<entity_id, component_value>>`
+local set_commands: { [id]: { [entity]: any } } = {}
+--- `map<component_id, array<entity_id>>`
+local remove_commands: { [id]: { entity } } = {}
+--- `array<entity_id>`
+local delete_commands: { entity } = {}
+
+type command_buffer = {
+    --- Execute all buffered commands and clear the buffer
+    flush: () -> (),
+
+    --- Adds a component to the entity with no value
+    add: (entity: entity, component: id) -> (),
+    --- Assigns a value to a component on the given entity
+    set: <T>(entity: entity, component: id<T>, data: T) -> (),
+    --- Removes a component from the given entity
+    remove: (entity: entity, component: id) -> (),
+    --- Deletes an entity from the world
+    delete: (entity: entity) -> (),
+}
+
+local function flush()
+    local adds = add_commands
+    local sets = set_commands
+    local removes = remove_commands
+    local deletes = delete_commands
+    table.clear(add_commands)
+    table.clear(set_commands)
+    table.clear(remove_commands)
+    table.clear(delete_commands)
+
+    for _, id in deletes do
+        world:delete(id)
+    end
+
+    for component, ids in adds do
+        for _, id in ids do
+            if deletes[id] then
+                continue
+            end
+
+            world:add(id, component)
+        end
+    end
+
+    for component, ids in sets do
+        for id, value in ids do
+            if deletes[id] then
+                continue
+            end
+
+            world:set(id, component, value)
+        end
+    end
+
+    for component, ids in removes do
+        for _, id in ids do
+            if deletes[id] then
+                continue
+            end
+
+            world:remove(id, component)
+        end
+    end
+end
+
+local function add(entity: entity, component: id)
+    if not add_commands[component] then
+        add_commands[component] = {}
+    end
+
+    table.insert(add_commands[component], entity)
+end
+
+local function set<T>(entity: entity, component: id<T>, data: T)
+    if not set_commands[component] then
+        set_commands[component] = {}
+    end
+
+    set_commands[component][entity] = data
+end
+
+local function remove(entity: entity, component: id)
+    if not remove_commands[component] then
+        remove_commands[component] = {}
+    end
+
+    table.insert(remove_commands[component], entity)
+end
+
+local function delete(entity: entity)
+    table.insert(delete_commands, entity)
+end
+
+local command_buffer: command_buffer = {
+    flush = flush,
+
+    add = add,
+    set = set,
+    remove = remove,
+    delete = delete,
+}
+
+return command_buffer