Starting entities, components, and levels

entity/entity.go

@@ -0,0 +1,43 @@
+package entity
+
+type Entity struct {
+
+	// Byte 1: Generation; Byte 2: Flags; Bytes 3-8: Index
+	ID    uint64
+	Comps []Comp
+}
+
+type Comp interface {
+	Name() string
+}
+
+func AddComp(e *Entity, c Comp) {
+	e.Comps = append(e.Comps, c)
+}
+
+func GetComp[T Comp](e *Entity) (out T) {
+
+	for i := 0; i < len(e.Comps); i++ {
+
+		comp, ok := e.Comps[i].(T)
+		if ok {
+			return comp
+		}
+	}
+
+	return out
+}
+
+func GetAllCompOfType[T Comp](e *Entity) (out []T) {
+
+	out = []T{}
+	for i := 0; i < len(e.Comps); i++ {
+
+		comp, ok := e.Comps[i].(T)
+		if ok {
+			out = append(out, comp)
+		}
+	}
+
+	return out
+}

entity/registry.go

@@ -0,0 +1,35 @@
+package entity
+
+import "github.com/bloeys/nmage/assert"
+
+type Registry struct {
+	EntityCount uint64
+	Entities    []Entity
+}
+
+func (r *Registry) NewEntity() *Entity {
+
+	assert.T(r.EntityCount < uint64(len(r.Entities)), "Can not add more entities to registry because it is full")
+
+	for i := 0; i < len(r.Entities); i++ {
+
+		// @TODO: Implement generational indices
+		e := &r.Entities[i]
+		if e.ID == 0 {
+			r.EntityCount++
+			e.ID = uint64(i) + 1
+
+			assert.T(e.ID != 0, "Entity ID must not be zero")
+			return e
+		}
+	}
+
+	panic("failed to create new entity because we did not find a free spot in the registry. Why did the assert not go off?")
+}
+
+func NewRegistry(size uint32) *Registry {
+	assert.T(size > 0, "Registry size must be more than zero")
+	return &Registry{
+		Entities: make([]Entity, size),
+	}
+}