using UnityEngine;
using System.Collections;


namespace WorldStreamer2
{
    /// <summary>
    /// Terrain culling system.
    /// </summary>
    public class TerrainCullingSystem : MonoBehaviour
    {

        [Tooltip("Max view distance is referred from camera to terrain center point")]



        /// <summary>
        /// The bounding distance - Max view distance is referred from camera to terrain center point.
        /// </summary>
        public float renderingDistance = 10000;


        float sphereSize = 0.5f;

        Terrain terrain;

        CullingGroup group;
        BoundingSphere[] spheres = new BoundingSphere[1000];

        Vector3 offsetVector;
        Vector3 offsetVectorUp;
        Camera mainCamera;
        int heightSphereNumber;

        //[HideInInspector]
        //public bool disableTrees = false;

        /// <summary>
        /// Start this instance, generates culling group and finds terrain.
        /// </summary>
        void Start()
        {
            terrain = GetComponent<Terrain>();
            if (terrain != null)
            {

                if (terrain.terrainData.size.x > terrain.terrainData.size.z)
                    sphereSize = terrain.terrainData.size.x * 0.75f;
                else
                    sphereSize = terrain.terrainData.size.z * 0.75f;



                offsetVector = new Vector3(terrain.terrainData.size.x, 0, terrain.terrainData.size.z) * 0.5f;


                group = new CullingGroup();
                group.targetCamera = Camera.main;

                heightSphereNumber = 2 * (int)(terrain.terrainData.size.y / (float)sphereSize);
                heightSphereNumber = Mathf.Max(1, heightSphereNumber);
                offsetVectorUp = new Vector3(0, sphereSize * 0.5f, 0);

                for (int i = 0; i < heightSphereNumber; i++)
                {

                    spheres[i] = new BoundingSphere(transform.position + offsetVector + i * offsetVectorUp, sphereSize);

                }


                group.SetBoundingSpheres(spheres);
                group.SetBoundingSphereCount(heightSphereNumber);

                group.onStateChanged = StateChangedMethod;


                group.SetBoundingDistances(new float[] { renderingDistance });

                mainCamera = Camera.main;
                group.SetDistanceReferencePoint(Camera.main.transform);


                Invoke("CheckVisibility", 0.1f);



            }
            else
                Debug.LogError("TerrainCullingSystem: no terrain on game object " + gameObject.name);


        }

        void OnDrawGizmosSelected()
        {
            Gizmos.color = Color.red;

            for (int i = 0; i < heightSphereNumber; i++)
            {
                Gizmos.DrawWireSphere(transform.position + offsetVector + i * offsetVectorUp, sphereSize);

            }

        }

        /// <summary>
        /// Checks visibility by hand
        /// </summary>
        void CheckVisibility()
        {

            bool visible = false;
            for (int i = 0; i < heightSphereNumber; i++)
            {
                if (group.IsVisible(i))
                {
                    visible = true;
                    break;
                }
            }

            if (!visible)
            {

                terrain.drawHeightmap = false;
                //if (disableTrees)
                terrain.drawTreesAndFoliage = false;
            }

        }

        /// <summary>
        /// sets object possition, and checks camera change;
        /// </summary>
        public void Update()
        {

            for (int i = 0; i < heightSphereNumber; i++)
            {
                spheres[i] = new BoundingSphere(transform.position + offsetVector + i * offsetVectorUp, sphereSize);
            }

            if (mainCamera != Camera.main)
            {
                mainCamera = Camera.main;
                group.SetDistanceReferencePoint(Camera.main.transform);
            }

        }

        /// <summary>
        /// Event on cilling group change
        /// </summary>
        /// <param name="evt">Evt.</param>
        private void StateChangedMethod(CullingGroupEvent evt)
        {

            bool visible = false;
            for (int i = 0; i < heightSphereNumber; i++)
            {
                if (group.IsVisible(i))
                {
                    visible = true;
                    break;
                }
            }

            if (visible)
            {

                terrain.drawHeightmap = true;
                //if (disableTrees)
                terrain.drawTreesAndFoliage = true;

            }
            else
            {

                terrain.drawHeightmap = false;
                //if (disableTrees)
                terrain.drawTreesAndFoliage = false;

            }

        }

        /// <summary>
        /// Raises the disable event.
        /// </summary>
        void OnDisable()
        {
            if (group != null)
            {
                group.Dispose();
                group = null;
            }
        }


    }
}