using UnityEngine;
using UnityEngine.Experimental.TerrainAPI;
using UnityEditor.ShortcutManagement;

namespace UnityEditor.Experimental.TerrainAPI
{
    internal class ThermalErosionTool : TerrainPaintTool<ThermalErosionTool>, IValidationTests
    {
#if UNITY_2019_1_OR_NEWER
        [Shortcut("Terrain/Select Thermal Erosion Tool", typeof(TerrainToolShortcutContext))]               // tells shortcut manager what to call the shortcut and what to pass as args
        static void SelectShortcut(ShortcutArguments args) {
            TerrainToolShortcutContext context = (TerrainToolShortcutContext)args.context;          // gets interface to modify state of TerrainTools
            context.SelectPaintTool<ThermalErosionTool>();                                                                        // set active tool
            TerrainToolsAnalytics.OnShortcutKeyRelease("Select Thermal Erosion Tool");
        }
#endif

        [SerializeField]
        IBrushUIGroup m_commonUI;
        private IBrushUIGroup commonUI
        {
            get
            {
                if( m_commonUI == null )
                {
                    m_commonUI = new DefaultBrushUIGroup( "ThermalErosion", UpdateAnalyticParameters );
                    m_commonUI.OnEnterToolMode();
                }

                return m_commonUI;
            }
        }

        Erosion.ThermalEroder m_Eroder = null;

        public override void OnEnable() {
            base.OnEnable();
            m_Eroder = new Erosion.ThermalEroder();
            m_Eroder.OnEnable();
        }

        public override void OnEnterToolMode() {
            base.OnEnterToolMode();
            commonUI.OnEnterToolMode();
        }

        public override void OnExitToolMode() {
            base.OnExitToolMode();
            commonUI.OnExitToolMode();
        }

        #region Resources
        Material m_Material = null;
        Material GetPaintMaterial()
        {
            if (m_Material == null)
                m_Material = new Material(Shader.Find("Hidden/TerrainTools/SimpleHeightBlend"));
            return m_Material;
        }

        Material m_SplatMaterial = null;
        Material GetSplatMaterial()
        {
            if (m_SplatMaterial == null)
                m_SplatMaterial = new Material(Shader.Find("Hidden/TerrainTools/SedimentSplat"));
            return m_SplatMaterial;
        }
        #endregion

        #region GUI
        public override string GetName()
        {
            return "Erosion/Thermal";
        }

        public override string GetDesc()
        {
            return "Thermal Erosion\n" +
                "Simulates thermal erosion from freezing / thawing processes, and the resulting avalanching of debris\n";
        }

        public override void OnSceneGUI(Terrain terrain, IOnSceneGUI editContext)
        {
            commonUI.OnSceneGUI2D(terrain, editContext);

            // only do the rest if user mouse hits valid terrain or they are using the
            // brush parameter hotkeys to resize, etc
            if (!editContext.hitValidTerrain && !commonUI.isInUse)
            {
                return;
            }

            // update brush UI group
            commonUI.OnSceneGUI(terrain, editContext);

            // dont render preview if this isnt a repaint. losing performance if we do
            if (Event.current.type != EventType.Repaint)
            {
                return;
            }

            using(IBrushRenderPreviewUnderCursor brushRender = new BrushRenderPreviewUIGroupUnderCursor(commonUI, "ThermalErosion", editContext.brushTexture))
            {
                if(brushRender.CalculateBrushTransform(out BrushTransform brushXform))
                {
                    PaintContext ctx = brushRender.AcquireHeightmap(false, brushXform.GetBrushXYBounds(), 1);
                
                    brushRender.RenderBrushPreview(ctx, TerrainPaintUtilityEditor.BrushPreview.SourceRenderTexture, brushXform, TerrainPaintUtilityEditor.GetDefaultBrushPreviewMaterial(), 0);
                }
            }
        }

        bool m_ShowControls = true;
        bool m_ShowAdvancedUI = false;
        string[] m_MatNames = {
                    "Custom",
                    "Dry Ash",    // 40
                    "Chalk",      // 45
                    "Dry Clay",   // 25 - 40
                    "Wet Clay",   // 15
                    "Soil",       // 30-45
                    "Granite Scree", // 35 - 40
                    "Gravel", //45 - 45
                    "Dry Sand",
                    "Wet Sand",
                    "Quick Sand",
                    "Snow"
                };

        float[,] m_TauValues = new float[,] {
                    { -1.0f, -1.0f },  //custom
                    { 38.0f, 42.0f },  //dry ash
                    { 45.0f, 45.0f },  //chalk
                    { 25.0f, 40.0f },  //dry clay (25 - 40)
                    { 15.0f, 15.0f },  //wet clay 
                    { 30.0f, 45.0f },  //soil (30-45)
                    { 35.0f, 40.0f },  //crushed granite (35 - 40) 
                    { 45.0f, 45.0f },  //gravel
                    { 32.0f, 36.0f },  //dry sand
                    { 45.0f, 45.0f },  //wet sand
                    { 15.0f, 30.0f },  //quicksand (15-30)
                    { 38.0f, 38.0f }   //snow
                };
        public override void OnInspectorGUI(Terrain terrain, IOnInspectorGUI editContext)
        {
            EditorGUI.BeginChangeCheck();

            commonUI.OnInspectorGUI(terrain, editContext);
            commonUI.validationMessage = ValidateAndGenerateUserMessage(terrain);

            m_ShowControls = TerrainToolGUIHelper.DrawHeaderFoldoutForErosion(Erosion.Styles.m_ThermalErosionControls, m_ShowControls, m_Eroder.ResetTool);

            if (m_ShowControls) {

                EditorGUILayout.BeginVertical("GroupBox");

               

                EditorGUI.BeginChangeCheck();
                m_Eroder.m_MatPreset = EditorGUILayout.Popup(Erosion.Styles.m_MatPreset, m_Eroder.m_MatPreset, m_MatNames);
                if (EditorGUI.EndChangeCheck() && m_Eroder.m_MatPreset != 0) {
                    m_Eroder.m_AngleOfRepose.x = m_TauValues[m_Eroder.m_MatPreset, 0];
                    m_Eroder.m_AngleOfRepose.y = m_TauValues[m_Eroder.m_MatPreset, 1];
                }

                EditorGUI.indentLevel++;
                m_ShowAdvancedUI = TerrainToolGUIHelper.DrawSimpleFoldout(new GUIContent("Advanced"), m_ShowAdvancedUI);
                if (m_ShowAdvancedUI) {
                    m_Eroder.m_ThermalIterations = EditorGUILayout.IntSlider(Erosion.Styles.m_NumIterations, m_Eroder.m_ThermalIterations, 1, 1000);
                    m_Eroder.m_dt = EditorGUILayout.Slider(Erosion.Styles.m_TimeDelta, m_Eroder.m_dt, 0.00001f, 0.05f);

                    EditorGUI.BeginChangeCheck();
                    EditorGUILayout.MinMaxSlider(Erosion.Styles.m_AngleOfRepose, ref m_Eroder.m_AngleOfRepose.x, ref m_Eroder.m_AngleOfRepose.y, 0.0f, 90.0f);
                    if (EditorGUI.EndChangeCheck()) {
                        m_Eroder.m_MatPreset = 0; //we changed the angle of repose, so now we should switch the UI to "Custom"
                    }

                    m_Eroder.m_ReposeJitter = EditorGUILayout.IntSlider(Erosion.Styles.m_AngleOfReposeJitter, (int)m_Eroder.m_ReposeJitter, 0, 100);
                }

                EditorGUILayout.EndVertical();
            }

            if (EditorGUI.EndChangeCheck()) {
                Save(true);
                TerrainToolsAnalytics.OnParameterChange();
            }
        }
        #endregion

        #region Paint

        private void AddHeight(Terrain terrain, IOnPaint editContext) {
            using(IBrushRenderUnderCursor brushRender = new BrushRenderUIGroupUnderCursor(commonUI, "ThermalErosion", editContext.brushTexture))
            {
                if(brushRender.CalculateBrushTransform(out BrushTransform brushXform))
                {
                    PaintContext paintContext = brushRender.AcquireHeightmap(true, brushXform.GetBrushXYBounds(), 1);
                
                    paintContext.sourceRenderTexture.filterMode = FilterMode.Bilinear;
                    Material mat = TerrainPaintUtility.GetBuiltinPaintMaterial();
                    float brushStrength = Event.current.shift ? -m_Eroder.m_AddHeightAmt : m_Eroder.m_AddHeightAmt;
                    brushStrength *= (commonUI.brushStrength);

                    if(Event.current.control) { brushStrength = 0.0f; }

                    Vector4 brushParams = new Vector4(0.0001f * brushStrength, 0.0f, 0.0f, 0.0f);
                    mat.SetTexture("_BrushTex", editContext.brushTexture);
                    mat.SetVector("_BrushParams", brushParams);

                    brushRender.SetupTerrainToolMaterialProperties(paintContext, brushXform, mat);
                    brushRender.RenderBrush(paintContext, mat, (int)TerrainPaintUtility.BuiltinPaintMaterialPasses.RaiseLowerHeight);
                }
            }
        }

        public override bool OnPaint(Terrain terrain, IOnPaint editContext)
        {
            commonUI.OnPaint(terrain, editContext);

            if(!commonUI.allowPaint) { return false; }

            int[] numWorkGroups = { 8, 8, 1 };

            using(IBrushRenderUnderCursor brushRender = new BrushRenderUIGroupUnderCursor(commonUI, "ThermalErosion", editContext.brushTexture))
            {
                if(brushRender.CalculateBrushTransform(out BrushTransform brushXform))
                {
                    PaintContext paintContext = brushRender.AcquireHeightmap(true, brushXform.GetBrushXYBounds(), 1);
                    paintContext.sourceRenderTexture.filterMode = FilterMode.Bilinear;
    
                    //figure out what size we need our render targets to be
                    Rect brushRect = brushXform.GetBrushXYBounds();

                    m_Eroder.inputTextures["Height"] = paintContext.sourceRenderTexture;
                    
                    Vector2 texelSize = new Vector2(terrain.terrainData.size.x / terrain.terrainData.heightmapResolution,
                                                    terrain.terrainData.size.z / terrain.terrainData.heightmapResolution);
                    m_Eroder.ErodeHeightmap(terrain.terrainData.size, brushRect, texelSize);

                    Material mat = GetPaintMaterial();
                    var brushMask = RTUtils.GetTempHandle(paintContext.sourceRenderTexture.width, paintContext.sourceRenderTexture.height, 0, FilterUtility.defaultFormat);
                    Utility.SetFilterRT(commonUI, paintContext.sourceRenderTexture, brushMask, mat);
                    Vector4 brushParams = new Vector4(commonUI.brushStrength, 0.0f, 0.0f, 0.0f);
                    mat.SetTexture("_BrushTex", editContext.brushTexture);
                    mat.SetTexture("_NewHeightTex", m_Eroder.outputTextures["Height"]);
                    mat.SetVector("_BrushParams", brushParams);

                    brushRender.SetupTerrainToolMaterialProperties(paintContext, brushXform, mat);
                    brushRender.RenderBrush(paintContext, mat, 0);
                    RTUtils.Release(brushMask);
                }
            }

            return true;
        }
        #endregion

        #region IValidationTests
        public virtual string ValidateAndGenerateUserMessage(Terrain terrain)
        {
            if (terrain.terrainData.heightmapResolution < 1025)
                return "Erosion tools work best with a heightmap resolution of 1025 or greater.";

            return "";

        }

        #endregion

        #region Analytics
        private TerrainToolsAnalytics.IBrushParameter[] UpdateAnalyticParameters() => new TerrainToolsAnalytics.IBrushParameter[]{
            new TerrainToolsAnalytics.BrushParameter<string>{Name = Erosion.Styles.m_MatPreset.text, Value = m_MatNames[m_Eroder.m_MatPreset]},
            new TerrainToolsAnalytics.BrushParameter<float>{Name = Erosion.Styles.m_NumIterations.text, Value = m_Eroder.m_ThermalIterations},
            new TerrainToolsAnalytics.BrushParameter<float>{Name = Erosion.Styles.m_TimeDelta.text, Value = m_Eroder.m_dt},
            new TerrainToolsAnalytics.BrushParameter<Vector2>{Name = Erosion.Styles.m_AngleOfRepose.text, Value = m_Eroder.m_AngleOfRepose},
            new TerrainToolsAnalytics.BrushParameter<float>{Name = Erosion.Styles.m_AngleOfReposeJitter.text, Value = m_Eroder.m_ReposeJitter},
        };
        #endregion
    }
}