Merge pull request #49 from yohamta/develop

add hierarchy package

README.md

@@ -19,6 +19,7 @@ It aims to be a feature rich and high performance [ECS Library](https://en.wikip
   - [Queries](#queries)
   - [Tags](#tags)
   - [Systems (Experimental)](#systems-experimental)
+  - [Hierarchy (Experimental)](#hierarchy-experimental)
 - [Internal Design for `World`](#internal-design-for-world)
 - [How to contribute?](#how-to-contribute)
 - [Contributors](#contributors)
@@ -236,6 +237,14 @@ See [GoDoc](https://pkg.go.dev/github.com/yohamta/donburi/ecs) and [Example](htt
 
 *Note: ECS package is experimental and API is unstable*
 
+### Hierarchy (Experimental)
+
+The [Hierarchy package](https://github.com/yohamta/donburi/tree/hierarchy/ecs) provides Parent-Children relationship function.
+
+See [GoDoc](https://pkg.go.dev/github.com/yohamta/donburi/hierarchy) and [Example](https://github.com/yohamta/donburi/tree/main/hierarchy/example_test.go).
+
+*Note: Hierarchy package is experimental and API is unstable*
+
 ## Internal Design for `World`
 
 It is a bit complex, so please refer to the following diagram to understand it.

hierarchy/children.go

@@ -0,0 +1,20 @@
+package hierarchy
+
+import (
+	"github.com/yohamta/donburi"
+)
+
+type childrenData struct {
+	Children []donburi.Entity
+}
+
+var childrenComponent = donburi.NewComponentType[childrenData]()
+
+// GetChildren returns children of the entry.
+func GetChildren(entry *donburi.Entry) ([]donburi.Entity, bool) {
+	if entry.HasComponent(childrenComponent) {
+		c := donburi.Get[childrenData](entry, childrenComponent).Children
+		return c, true
+	}
+	return nil, false
+}

hierarchy/example_test.go

@@ -0,0 +1,66 @@
+package hierarchy
+
+import (
+	"testing"
+
+	"github.com/yohamta/donburi"
+	ecslib "github.com/yohamta/donburi/ecs"
+)
+
+func TestParent(t *testing.T) {
+	w := donburi.NewWorld()
+	ecs := ecslib.NewECS(w)
+
+	ecs.AddSystem(ecslib.System{
+		Update: HierarchySystem.RemoveChildren,
+	})
+
+	parent := donburi.NewTag().SetName("parent")
+	child := donburi.NewTag().SetName("child")
+	grandChild := donburi.NewTag().SetName("grandChild")
+
+	pe := w.Entry(w.Create(parent))
+	ce := w.Entry(w.Create(child))
+	ge := w.Entry(w.Create(grandChild))
+
+	SetParent(pe, ce)
+	SetParent(ce, ge)
+
+	if p, ok := GetParent(ce); p != pe.Entity() || !ok {
+		t.Errorf("expected parent entity %d, got %d", pe.Entity(), p)
+	}
+
+	if p, ok := GetParent(ge); p != ce.Entity() || !ok {
+		t.Errorf("expected parent entity %d, got %d", ce.Entity(), p)
+	}
+
+	if _, ok := GetParent(pe); ok {
+		t.Errorf("expected parent entity %d, got %d", donburi.Null, pe.Entity())
+	}
+
+	children, ok := GetChildren(pe)
+	if !ok {
+		t.Errorf("expected children, got nil")
+	}
+	if children[0] != ce.Entity() {
+		t.Errorf("expected child entity %d, got %d", ce.Entity(), children[0])
+	}
+
+	children, ok = GetChildren(ce)
+	if children[0] != ge.Entity() {
+		t.Errorf("expected child entity %d, got %d", ge.Entity(), children[0])
+	}
+
+	pe.Remove()
+	ecs.Update()
+
+	if w.Valid(ce.Entity()) {
+		t.Errorf("expected child entity %d to be removed", ce.Entity())
+	}
+	if w.Valid(ge.Entity()) {
+		t.Errorf("expected grand child entity %d to be removed", ge.Entity())
+	}
+	if w.Len() != 0 {
+		t.Errorf("expected world to be empty")
+	}
+}

hierarchy/hierarchy.go

@@ -0,0 +1,30 @@
+package hierarchy
+
+import (
+	"github.com/yohamta/donburi"
+	"github.com/yohamta/donburi/ecs"
+	"github.com/yohamta/donburi/filter"
+	"github.com/yohamta/donburi/query"
+)
+
+// HierarchySystem is a system that removes children of invalid parents.
+var HierarchySystem = &parent{
+	query: query.NewQuery(filter.Contains(parentComponent)),
+}
+
+func (ps *parent) RemoveChildren(ecs *ecs.ECS) {
+	ps.query.EachEntity(ecs.World, func(entry *donburi.Entry) {
+		if p, ok := GetParent(entry); ok {
+			if ecs.World.Valid(p) {
+				return
+			}
+			c, ok := GetChildren(entry)
+			if ok {
+				for _, e := range c {
+					ecs.World.Remove(e)
+				}
+			}
+			entry.Remove()
+		}
+	})
+}

hierarchy/parent.go

@@ -0,0 +1,45 @@
+package hierarchy
+
+import (
+	"github.com/yohamta/donburi"
+	"github.com/yohamta/donburi/query"
+)
+
+type parentData struct {
+	Parent donburi.Entity
+}
+
+var parentComponent = donburi.NewComponentType[parentData]()
+
+// GetParent returns a parent of the entry.
+func GetParent(entry *donburi.Entry) (donburi.Entity, bool) {
+	if entry.HasComponent(parentComponent) {
+		p := donburi.Get[parentData](entry, parentComponent).Parent
+		return p, true
+	}
+	return donburi.Null, false
+}
+
+// SetParent sets a parent of the entry.
+func SetParent(parent *donburi.Entry, child *donburi.Entry) {
+	if !parent.Valid() {
+		panic("parent is not valid")
+	}
+	if !child.Valid() {
+		panic("child is not valid")
+	}
+	if child.HasComponent(parentComponent) {
+		panic("child already has a parent")
+	}
+	if !parent.HasComponent(childrenComponent) {
+		parent.AddComponent(childrenComponent)
+	}
+	child.AddComponent(parentComponent)
+	donburi.SetValue(child, parentComponent, parentData{Parent: parent.Entity()})
+	children := donburi.Get[childrenData](parent, childrenComponent)
+	children.Children = append(children.Children, child.Entity())
+}
+
+type parent struct {
+	query *query.Query
+}