using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

namespace GraphicsCat
{
    [ExecuteAlways]
    public class ShadowDistance : MonoBehaviour
    {
        public enum Mode
        {
            Static,
            Dynamic
        }

        public Mode mode = Mode.Static;

        [EnableIf(nameof(mode), CompareFunction.Equal, Mode.Static)]
        [Range(1f, 100f)]
        public float staticDistance = 10f;

        [InspectorDisplayName("Dynamic Distance Target")]
        [EnableIf(nameof(mode), CompareFunction.Equal, Mode.Dynamic)]
        public GameObject dynamicDistanceTarget;

        [InspectorDisplayName("Dynamic Distance Offset")]
        [EnableIf(nameof(mode), CompareFunction.Equal, Mode.Dynamic)]
        public float dynamicDistanceOffset = 0f;

        float m_TargetHalfSize = 0;

        void OnEnable()
        {
            UpdateShadowDistance();
            UpdateDynamicDistanceTargetHalfSize();
        }

        void Update()
        {
            UpdateShadowDistance();
        }

        void OnValidate()
        {
            UpdateShadowDistance();
            UpdateDynamicDistanceTargetHalfSize();
        }

        void UpdateShadowDistance()
        {
            if (mode == Mode.Static)
                SetShadowDistance(staticDistance);
            else
                UpdateShadowDistanceByLookTarget();
        }

        void UpdateShadowDistanceByLookTarget()
        {
            var target = dynamicDistanceTarget;
            if (target == null)
                target = gameObject;

            Camera mainCamera = Camera.main;
            if (mainCamera == null)
                return;

            var targetDistance = (target.transform.position - mainCamera.transform.position).magnitude;
            var shadowDistance = targetDistance + m_TargetHalfSize + dynamicDistanceOffset;
            SetShadowDistance(shadowDistance);
        }

        float GetShadowDistance()
        {
            var uprAsset = GraphicsSettings.currentRenderPipeline as UniversalRenderPipelineAsset;
            if (uprAsset != null)
                return uprAsset.shadowDistance;
            else
                return QualitySettings.shadowDistance;
        }

        void SetShadowDistance(float val)
        {
            var urpAsset = GraphicsSettings.currentRenderPipeline as UniversalRenderPipelineAsset;
            if (urpAsset != null)
                urpAsset.shadowDistance = val;
            else
                QualitySettings.shadowDistance = val;
        }

        void UpdateDynamicDistanceTargetHalfSize()
        {
            var bounds = BoundsUtils.GetHierarchyBounds(dynamicDistanceTarget);
            m_TargetHalfSize = bounds.extents.magnitude;
        }
    }
}