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

namespace X.Rendering.Feature
{


    public class AutoExposureVolumeProfile : VolumeComponent, IPostProcessComponent
    {
        public const int rangeMin = -9; // ev
        public const int rangeMax = 9; // ev

        public static Vector4 GetHistogramScaleOffsetRes()
        {
            float diff = rangeMax - rangeMin;
            float scale = 1f / diff;
            float offset = -rangeMin * scale;
            return new Vector4(scale, offset, Screen.width, Screen.height);
        }

        public enum EyeAdaptation
        {
            /// <summary>
            /// Progressive (smooth) eye adaptation.
            /// </summary>
            Progressive,

            /// <summary>
            /// Fixed (instant) eye adaptation.
            /// </summary>
            Fixed
        }

        [Serializable]
        public sealed class EyeAdaptationParameter : VolumeParameter<EyeAdaptation> { }

        [Range(1f, 99f)]
        public Vector2Parameter filtering = new Vector2Parameter(new Vector2(50f, 95f));

        /// <summary>
        /// Minimum average luminance to consider for auto exposure (in EV).
        /// </summary>
        [Range(rangeMin, rangeMax), InspectorName("Minimum (EV)")]
        public FloatParameter minLuminance = new FloatParameter (0f);

        /// <summary>
        /// Maximum average luminance to consider for auto exposure (in EV).
        /// </summary>
        [Range(rangeMin, rangeMax), InspectorName("Maximum (EV)")]
        public FloatParameter maxLuminance = new FloatParameter (0f);

        /// <summary>
        /// Middle-grey value. Use this to compensate the global exposure of the scene.
        /// </summary>
        [Min(0f), InspectorName("Exposure Compensation"), Tooltip("Use this to scale the global exposure of the scene.")]
        public FloatParameter exposureCompensation = new FloatParameter (1f);

        /// <summary>
        /// The type of eye adaptation to use.
        /// </summary>
        [InspectorName("Type"), Tooltip("Use \"Progressive\" if you want auto exposure to be animated. Use \"Fixed\" otherwise.")]
        public EyeAdaptationParameter eyeAdaptation = new EyeAdaptationParameter() { value = EyeAdaptation.Progressive };

        /// <summary>
        /// The adaptation speed from a dark to a light environment.
        /// </summary>
        [Min(0f), Tooltip("Adaptation speed from a dark to a light environment.")]
        public FloatParameter speedUp = new FloatParameter (2f);

        /// <summary>
        /// The adaptation speed from a light to a dark environment.
        /// </summary>
        [Min(0f), Tooltip("Adaptation speed from a light to a dark environment.")]
        public FloatParameter speedDown = new FloatParameter (1f);


        public bool IsActive() => filtering.overrideState;

        public bool IsTileCompatible()
        {
            return true;
        }
    }
}