gohan/component.go

package gohan

import (
	"sync"
)

var componentMutex sync.Mutex

// ComponentID is a component identifier. Each Component is assigned a unique ID
// via NewComponentID, and implements a ComponentID method returning its ID.
type ComponentID int

// Component represents data for an entity, and how it interacts with the world.
type Component interface {
	ComponentID() ComponentID
}

// NewComponentID returns the next available ComponentID.
func (w *World) NewComponentID() ComponentID {
	entityMutex.Lock()
	defer entityMutex.Unlock()

	componentMutex.Lock()
	defer componentMutex.Unlock()

	w.maxComponentID++

	for i := Entity(1); i <= w.maxEntityID; i++ {
		w.components[i] = append(w.components[i], nil)
	}

	return w.maxComponentID
}

// AddComponent adds a Component to an Entity.
func (w *World) AddComponent(entity Entity, component Component) {
	componentMutex.Lock()
	defer componentMutex.Unlock()

	componentID := component.ComponentID()

	w.components[entity][componentID] = component

	entityMutex.Lock()
	defer entityMutex.Unlock()
	w.modifiedEntities = append(w.modifiedEntities, entity)
}

// Component gets a Component of an Entity.
func (w *World) Component(entity Entity, componentID ComponentID) interface{} {
	components := w.components[entity]
	if components == nil {
		return nil
	}
	return components[componentID]
}