// Crest Water System
// Copyright © 2024 Wave Harmonic. All rights reserved.

using UnityEditor;
using UnityEngine;
using UnityEngine.Rendering;
using WaveHarmonic.Crest.Editor;

namespace WaveHarmonic.Crest.ShallowWater.Editor
{
    [CustomPreview(typeof(ShallowWaterSimulation))]
    sealed class Preview : TexturePreview
    {
        RenderTexture _TemporaryRenderTexture;

        public override GUIContent GetPreviewTitle() => new("Shallow Water Simulation");
        protected override Texture OriginalTexture
        {
            get
            {
                if (_TemporaryRenderTexture != null) return _TemporaryRenderTexture;
                // Return on of the textures to prove initialization.
                var target = this.target as ShallowWaterSimulation;
                return target._GroundHeight;
            }
        }

        public override void OnPreviewSettings()
        {
            base.OnPreviewSettings();
            // OnPreviewSettings is called after OnPreviewGUI so release here.
            RenderTexture.ReleaseTemporary(_TemporaryRenderTexture);
            _TemporaryRenderTexture = null;
        }

        public override void Cleanup()
        {
            base.Cleanup();
            RenderTexture.ReleaseTemporary(_TemporaryRenderTexture);
        }

        public override void OnPreviewGUI(Rect rect, GUIStyle background)
        {
            var target = this.target as ShallowWaterSimulation;
            var descriptor = target._GroundHeight.descriptor;
            descriptor.dimension = TextureDimension.Tex2DArray;
            descriptor.volumeDepth = target._WaterLevel != null ? 6 : 5;
            descriptor.useMipMap = false;

            // Copy textures to a single texture array.
            _TemporaryRenderTexture = RenderTexture.GetTemporary(descriptor);
            Graphics.CopyTexture(target._GroundHeight, 0, _TemporaryRenderTexture, 0);
            Graphics.CopyTexture(target._Height1, 0, _TemporaryRenderTexture, 1);
            Graphics.CopyTexture(target._VelocityX, 0, 0, _TemporaryRenderTexture, 2, 0);
            Graphics.CopyTexture(target._VelocityY, 0, 0, _TemporaryRenderTexture, 3, 0);
            Graphics.CopyTexture(target._Mask, 0, _TemporaryRenderTexture, 4);
            if (target._WaterLevel != null) Graphics.CopyTexture(target._WaterLevel, 0, _TemporaryRenderTexture, 5);

            _TemporaryRenderTexture.name = _Slice switch
            {
                0 => "Ground Height",
                1 => "Height",
                2 => "Velocity X",
                3 => "Velocity Y",
                4 => "Mask",
                5 => "Water Level",
                _ => throw new System.NotImplementedException(),
            };

            base.OnPreviewGUI(rect, background);
        }
    }
}