Basic system and window creation.

system.go

@@ -0,0 +1,68 @@
+package goga
+
+import ()
+
+// A system provides logic for actors satisfying required components.
+// They are automatically updated on each frame.
+type System interface {
+	Update(float64)
+	Add(actor *Actor) bool
+	Remove(actor *Actor) bool
+	RemoveById(id ActorId) bool
+	RemoveAll()
+	Len() int
+	GetName() string
+}
+
+var (
+	systems []System
+)
+
+// Adds a system to the game.
+// Returns false if the system exists already.
+func AddSystem(system System) bool {
+	for _, sys := range systems {
+		if sys == system {
+			return false
+		}
+	}
+
+	systems = append(systems, system)
+
+	return true
+}
+
+// Removes the given system.
+// Returns false if it could not be found.
+func RemoveSystem(system System) bool {
+	for i, sys := range systems {
+		if sys == system {
+			systems = append(systems[:i], systems[i+1:]...)
+			return true
+		}
+	}
+
+	return false
+}
+
+// Removes all systems.
+func RemoveAllSystems() {
+	systems = make([]System, 0)
+}
+
+// Finds and returns a system by name, or nil if not found.
+func GetSystemByName(name string) System {
+	for _, system := range systems {
+		if system.GetName() == name {
+			return system
+		}
+	}
+
+	return nil
+}
+
+func updateSystems(delta float64) {
+	for _, system := range systems {
+		system.Update(delta)
+	}
+}