/Framework/Nine/SceneQuery.cs

namespace Nine

{

    using System;

    using System.Collections.Generic;

    using Microsoft.Xna.Framework;



    /// <summary>

    /// Traverses the scene hierarchy and find all the objects that implements T.

    /// </summary>

    class SceneQuery<T> : ISpatialQuery<T> where T : class

    {

        CollectionAdapter adapter;

        List<ISceneManager<ISpatialQueryable>> sceneManagers;

        IList<object> topLevelObjects;



        public SceneQuery(List<ISceneManager<ISpatialQueryable>> sceneManagers, IList<object> topLevelObjects, Predicate<T> condition)

        {

            this.sceneManagers = sceneManagers;

            this.topLevelObjects = topLevelObjects;

            this.adapter = new CollectionAdapter(condition);

        }



        public void FindAll(ref BoundingSphere boundingSphere, ICollection<T> result)

        {

            adapter.Result = result;

            adapter.IncludeTopLevelNonSpatialQueryableDesendants(topLevelObjects);



            var count = sceneManagers.Count;

            for (int i = 0; i < count; ++i)

                sceneManagers[i].FindAll(ref boundingSphere, adapter);



            adapter.Result = null;

        }



        public void FindAll(ref Ray ray, ICollection<T> result)

        {

            adapter.Result = result;

            adapter.IncludeTopLevelNonSpatialQueryableDesendants(topLevelObjects);



            var count = sceneManagers.Count;

            for (int i = 0; i < count; ++i)

                sceneManagers[i].FindAll(ref ray, adapter);



            adapter.Result = null;

        }



        public void FindAll(ref BoundingBox boundingBox, ICollection<T> result)

        {

            adapter.Result = result;

            adapter.IncludeTopLevelNonSpatialQueryableDesendants(topLevelObjects);



            var count = sceneManagers.Count;

            for (int i = 0; i < count; ++i)

                sceneManagers[i].FindAll(ref boundingBox, adapter);



            adapter.Result = null;

        }



        public void FindAll(BoundingFrustum boundingFrustum, ICollection<T> result)

        {

            adapter.Result = result;

            adapter.IncludeTopLevelNonSpatialQueryableDesendants(topLevelObjects);



            var count = sceneManagers.Count;

            for (int i = 0; i < count; ++i)

                sceneManagers[i].FindAll(boundingFrustum, adapter);



            adapter.Result = null;

        }



        class CollectionAdapter : SpatialQueryCollectionAdapter<ISpatialQueryable>

        {

            public ICollection<T> Result;

            private ISpatialQueryable currentItem;

            private Func<object, TraverseOptions> traverser;

            private Predicate<T> condition;



            public CollectionAdapter(Predicate<T> condition)

            {

                this.condition = condition;

                this.traverser = new Func<object, TraverseOptions>(FindNonSpatialQueryableDescendantTraverser);

            }



            public override void Add(ISpatialQueryable item)

            {

                currentItem = item;

                ContainerTraverser.Traverse(item, traverser);

                currentItem = null;

            }

            

            public void IncludeTopLevelNonSpatialQueryableDesendants(IList<object> topLevelObjects)

            {

                var count = topLevelObjects.Count;

                for (int i = 0; i < count; ++i)

                {

                    ContainerTraverser.Traverse(topLevelObjects[i], traverser);

                }

            }



            private TraverseOptions FindNonSpatialQueryableDescendantTraverser(object item)

            {

                T t;



                // Skip ISpatialQueryables since they are explicitly added to the scene manager,

                // but only if it doesn't equal to the current T.

                var queryable = item as ISpatialQueryable;

                if (queryable != null)

                {

                    if (queryable == currentItem)

                    {

                        t = queryable as T;

                        if (t != null && (condition == null || condition(t)))

                            Result.Add(t);

                        return TraverseOptions.Continue;

                    }

                    return TraverseOptions.Skip;

                }



                t = item as T;

                if (t != null && (condition == null || condition(t)))

                    Result.Add(t);

                return TraverseOptions.Continue;

            }

        }

    }

}