simple ecs system

server/internal/ecs/system.go

@@ -0,0 +1,49 @@
+package ecs
+
+import "reflect"
+
+type System interface {
+	Update(w *World)
+}
+
+type funcsystem struct {
+	update reflect.Value
+	args   func(w *World) []Storage
+}
+
+func FuncSystem(F any) System {
+	f := reflect.ValueOf(F)
+	in := f.Type().NumIn()
+	argTypes := make([]reflect.Type, in)
+	for i := 0; i < in; i++ {
+		argTypes[i] = f.Type().In(i)
+	}
+	return &funcsystem{
+		update: f,
+		args: func(w *World) (args []Storage) {
+			args = make([]Storage, in)
+			for i := 0; i < in; i++ {
+				args[i] = w.GetResourceRaw(argTypes[i]).(Storage)
+			}
+			return
+		},
+	}
+}
+
+func (f *funcsystem) Update(w *World) {
+	storages := f.args(w)
+	if len(storages) == 0 {
+		return
+	}
+	eids := storages[0].BitSet()
+	for _, v := range storages[1:] {
+		eids = eids.And(v.BitSet())
+	}
+	args := make([]reflect.Value, len(storages))
+	eids.Range(func(eid Index) {
+		for i := range args {
+			args[i] = reflect.ValueOf(storages[i].Get(eid))
+		}
+		f.update.Call(args)
+	})
+}