/************************************************************************************
Copyright : Copyright (c) Facebook Technologies, LLC and its affiliates. All rights reserved.

Your use of this SDK or tool is subject to the Oculus SDK License Agreement, available at
https://developer.oculus.com/licenses/oculussdk/

Unless required by applicable law or agreed to in writing, the Utilities SDK distributed
under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
ANY KIND, either express or implied. See the License for the specific language governing
permissions and limitations under the License.
************************************************************************************/

using System.Collections.Generic;

namespace UnityEngine.EventSystems
{
    /// <summary>
    /// Simple event system using physics raycasts. Very closely based on UnityEngine.EventSystems.PhysicsRaycaster
    /// </summary>
    [RequireComponent(typeof(OVRCameraRig))]
    public class OVRPhysicsRaycaster : BaseRaycaster
    {
        /// <summary>
        /// Const to use for clarity when no event mask is set
        /// </summary>
        protected const int kNoEventMaskSet = -1;


        /// <summary>
        /// Layer mask used to filter events. Always combined with the camera's culling mask if a camera is used.
        /// </summary>
        [SerializeField]
        protected LayerMask m_EventMask = kNoEventMaskSet;

        protected OVRPhysicsRaycaster()
        { }

        public override Camera eventCamera
        {
            get
            {
                return GetComponent<OVRCameraRig>().leftEyeCamera;
            }
        }

        /// <summary>
        /// Depth used to determine the order of event processing.
        /// </summary>
        public virtual int depth
        {
            get { return (eventCamera != null) ? (int)eventCamera.depth : 0xFFFFFF; }
        }

        public int sortOrder = 0;
        public override int sortOrderPriority
        {
            get
            {
                return sortOrder;
            }
        }

        /// <summary>
        /// Event mask used to determine which objects will receive events.
        /// </summary>
        public int finalEventMask
        {
            get { return (eventCamera != null) ? eventCamera.cullingMask & m_EventMask : kNoEventMaskSet; }
        }

        /// <summary>
        /// Layer mask used to filter events. Always combined with the camera's culling mask if a camera is used.
        /// </summary>
        public LayerMask eventMask
        {
            get { return m_EventMask; }
            set { m_EventMask = value; }
        }


        /// <summary>
        /// Perform a raycast using the worldSpaceRay in eventData.
        /// </summary>
        /// <param name="eventData"></param>
        /// <param name="resultAppendList"></param>
        public override void Raycast(PointerEventData eventData, List<RaycastResult> resultAppendList)
        {
            // This function is closely based on PhysicsRaycaster.Raycast

            if (eventCamera == null)
                return;

            if (!eventData.IsVRPointer())
                return;

            var ray = eventData.GetRay();

            float dist = eventCamera.farClipPlane - eventCamera.nearClipPlane;

            var hits = Physics.RaycastAll(ray, dist, finalEventMask);

            if (hits.Length > 1)
                System.Array.Sort(hits, (r1, r2) => r1.distance.CompareTo(r2.distance));

            if (hits.Length != 0)
            {
                for (int b = 0, bmax = hits.Length; b < bmax; ++b)
                {
                    var result = new RaycastResult
                    {
                        gameObject = hits[b].collider.gameObject,
                        module = this,
                        distance = hits[b].distance,
                        index = resultAppendList.Count,
                        worldPosition = hits[0].point,
                        worldNormal = hits[0].normal,
                    };
                    resultAppendList.Add(result);
                }
            }
        }

        /// <summary>
        ///  Perform a Spherecast using the worldSpaceRay in eventData.
        /// </summary>
        /// <param name="eventData"></param>
        /// <param name="resultAppendList"></param>
        /// <param name="radius">Radius of the sphere</param>
        public void Spherecast(PointerEventData eventData, List<RaycastResult> resultAppendList, float radius)
        {
            if (eventCamera == null)
                return;

            if (!eventData.IsVRPointer())
                return;

            var ray = eventData.GetRay();


            float dist = eventCamera.farClipPlane - eventCamera.nearClipPlane;

            var hits = Physics.SphereCastAll(ray, radius, dist, finalEventMask);

            if (hits.Length > 1)
                System.Array.Sort(hits, (r1, r2) => r1.distance.CompareTo(r2.distance));

            if (hits.Length != 0)
            {
                for (int b = 0, bmax = hits.Length; b < bmax; ++b)
                {
                    var result = new RaycastResult
                    {
                        gameObject = hits[b].collider.gameObject,
                        module = this,
                        distance = hits[b].distance,
                        index = resultAppendList.Count,
                        worldPosition = hits[0].point,
                        worldNormal = hits[0].normal,
                    };
                    resultAppendList.Add(result);
                }
            }
        }
        /// <summary>
        /// Get screen position of this world position as seen by the event camera of this OVRPhysicsRaycaster
        /// </summary>
        /// <param name="worldPosition"></param>
        /// <returns></returns>
        public Vector2 GetScreenPos(Vector3 worldPosition)
        {
            // In future versions of Uinty RaycastResult will contain screenPosition so this will not be necessary
            return eventCamera.WorldToScreenPoint(worldPosition);
        }
    }
}