using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using Unity.Burst.CompilerServices;
using Unity.Collections;
using Unity.VisualScripting;
using UnityEditor;
using UnityEngine;

public class GrasFeld : MonoBehaviour
{
    float grasDichteProMeter = 1.6f;
    static float basisChunkGroese = 5f;

    public GameObject GrasChunkPrefab;

    public Dictionary<Vector2Int, ChunkData> allChunckData;
    List<Vector2Int> ChunksModifyed = new List<Vector2Int>();
    List<Vector2Int> ActiveChunks;

    public List<ChunkGameObject> AlleChunkObjekte = new List<ChunkGameObject>();

#if UNITY_EDITOR
    void OnEnable()
    {
        AssemblyReloadEvents.beforeAssemblyReload += OnBeforeAssemblyReload;
        AssemblyReloadEvents.afterAssemblyReload += OnAfterAssemblyReload;
    }

    void OnDisable()
    {
        AssemblyReloadEvents.beforeAssemblyReload -= OnBeforeAssemblyReload;
        AssemblyReloadEvents.afterAssemblyReload -= OnAfterAssemblyReload;
    }
    

    public void OnBeforeAssemblyReload()
    {
        ClearAllChunkData();
    }

    public void ClearAllChunkData()
    {
        if (allChunckData == null) return;

        var enumerator = allChunckData.GetEnumerator();
        while (enumerator.MoveNext())
        {
            var pair = enumerator.Current;
            pair.Value.Data.Dispose();
        }
        
        allChunckData.Clear();
    }
#endif

    public void OnAfterAssemblyReload()
    {

    }

    private void Update()
    {
        Vector3 cameraPosition = Camera.main.transform.position;
        foreach (var chunk in AlleChunkObjekte)
        {
            chunk.SetLOD(cameraPosition);
        }
    }


    public void GrasZeichnen(GrassortenScriptableObject sorte, Vector2 pos, float pinselRadius, bool zeichenInverter)
    {
        if (allChunckData == null) allChunckData = new Dictionary<Vector2Int, ChunkData>();
        List<ChunkData> zuÄnderndeChunks = new List<ChunkData>();



        //Alle chuncks finden in die Gezeichnet werden könnte
        ActiveChunks = GetActiveChunckPositions(pinselRadius, pos);
        foreach (var potential in ActiveChunks)
        {
            if(allChunckData.TryGetValue(potential, out var chunckData))
            {
                zuÄnderndeChunks.Add(chunckData);
            }
            else
            {
                allChunckData.Add(potential, new ChunkData(potential));
                if (allChunckData.TryGetValue(potential, out chunckData))
                    zuÄnderndeChunks.Add(chunckData);
                else
                    Debug.LogError("Konnte Chunk nich adden " + potential);
            }
        }

        ChunksModifyed.Clear();
        foreach(ChunkData chunk in zuÄnderndeChunks)
        {
            allChunckData[chunk.pos] = ZeichneInChunk(chunk, sorte, pos, pinselRadius, zeichenInverter);
            ChunksModifyed.Add(chunk.pos);

            if (allChunckData[chunk.pos].isEmpty == true)
            {
                allChunckData[chunk.pos].Data.Dispose();
                allChunckData.Remove(chunk.pos);
            }
        }



        MakeChunks();
    }

    public void MakeChunks()
    {

        List<ChunkGameObject> ChunkObjectsToRecalculate = new List<ChunkGameObject>();
        foreach(Vector2Int chunkPos in ChunksModifyed)
        {
            ChunkGameObject chunkObject;
            foreach (ChunkGameObject currenChunckObject in AlleChunkObjekte)
            {
                if (currenChunckObject.ContainsChunk(chunkPos))
                {
                    chunkObject = currenChunckObject;
                    goto ChunkExistiert;
                }
            }

            //Kein Chunk gefunden
            GameObject tempGO = Instantiate(GrasChunkPrefab);
            tempGO.transform.position = new Vector3(chunkPos.x, 0, chunkPos.y);
            tempGO.transform.parent = transform;
            tempGO.name = "Chunk LOD3";
            chunkObject = tempGO.GetComponent<ChunkGameObject>();
            chunkObject.SetPosToGrid();
            chunkObject.grasFeld = this;
            AlleChunkObjekte.Add(chunkObject);

        ChunkExistiert:
            chunkObject.SetUpdate(chunkPos);
            if(ChunkObjectsToRecalculate.Contains(chunkObject) == false)
                ChunkObjectsToRecalculate.Add(chunkObject);
        }

        foreach(var chunkObj in ChunkObjectsToRecalculate)
        {
            chunkObj.DoMeshUpdate();
        }



        return; 
        int count = 0;
        while (transform.childCount > count)
        {
            var checkPos = transform.GetChild(count).gameObject.GetComponent<ChunkGameObject>().pos;
            if (ChunksModifyed.Contains(checkPos))
            {
                DestroyImmediate(transform.GetChild(count).gameObject);
            }
            else
                count++;
        }

        foreach (var chunk in allChunckData)
        {
            if (ChunksModifyed.Contains(chunk.Key) == false)
                continue;

            Texture2D tempTextur = new Texture2D(16,16);

            for (int i = 0; i < 16; i++)
                for (int j = 0; j < 16; j++)
                {
                    tempTextur.SetPixel(i, j, new Color(chunk.Value.Data[i * 16 + j][0] * 256, 0, 0));
                }

            tempTextur.Apply();


            GameObject chunkObject = Instantiate(GrasChunkPrefab);
            chunkObject.transform.position = new Vector3(chunk.Key.x, 0, chunk.Key.y);
            chunkObject.transform.parent = transform;
            chunkObject.GetComponent<ChunkGameObject>().DebugGrasTextur = tempTextur;
            chunkObject.GetComponent<ChunkGameObject>().pos = chunk.Key;
            chunkObject.GetComponent<ChunkGameObject>().hasChanged = ChunksModifyed.Contains(chunk.Key);
            chunkObject.name = "" + chunk.Key;
        }

        ChunksModifyed.Clear();
    }


    static ChunkData ZeichneInChunk(ChunkData chunk, GrassortenScriptableObject grassorte, Vector2 pos, float brushSize, bool shift)
    {
        int grassortenIndex = -1;

        if (chunk.VerwendeteGrassorten.Contains(grassorte.grassorteId) == false)
            chunk.VerwendeteGrassorten.Add(grassorte.grassorteId);

        grassortenIndex = chunk.VerwendeteGrassorten.IndexOf(grassorte.grassorteId);

        int emptyCount = 0;
        for(int i = 0; i < 16; i++)
            for(int j = 0; j < 16; j++)
            {
                var currentValue = chunk.Data[i * 16 + j];

                byte val = currentValue[grassortenIndex];
                Vector2 inchunckPos = new Vector2(chunk.pos.x + i * (basisChunkGroese / 16f), chunk.pos.y + j * (basisChunkGroese / 16f));

                if (Vector2.Distance(inchunckPos, pos) < brushSize)
                    val = shift ? (byte)0 : (byte)255;

                currentValue[grassortenIndex] = val;
                if (currentValue[grassortenIndex] == 0)
                    emptyCount++;


                chunk.Data[i * 16 + j] = currentValue;
            }

        if (emptyCount == (16 * 16))
            chunk.isEmpty = true;

        return chunk;
    }


    List<Vector2Int> GetActiveChunckPositions(float brushRadius, Vector2 brushPos)
    {
        List<Vector2Int> activeChuncksTemp = new List<Vector2Int>();

        int minPosX = Mathf.FloorToInt((brushPos.x - brushRadius) / basisChunkGroese)   * (int)basisChunkGroese;
        int minPosY = Mathf.FloorToInt((brushPos.y - brushRadius) / basisChunkGroese)   * (int)basisChunkGroese;
        int maxPosX = Mathf.CeilToInt((brushPos.x + brushRadius) / basisChunkGroese)    * (int)basisChunkGroese;
        int maxPosY = Mathf.CeilToInt((brushPos.y + brushRadius) / basisChunkGroese)    * (int)basisChunkGroese;

        for (int x = minPosX; x < maxPosX; x += (int)basisChunkGroese)
        {
            for (int y = minPosY; y < maxPosY; y += (int)basisChunkGroese)
            {
                Vector2Int chunckPos = new Vector2Int(x, y);
                if (chunckPos.x < 0 || chunckPos.x > 1000 || chunckPos.y < 0 || chunckPos.y > 1000)
                    continue;

                if (IsChunckInRadius(brushPos, brushRadius, chunckPos, basisChunkGroese))
                    activeChuncksTemp.Add(chunckPos);
            }
        }

        return activeChuncksTemp;
    }

    static bool IsChunckInRadius(Vector2 pos, float radius, Vector2Int chunckPos, float chunckSize)
    {
        // Find the closest point to the circle within the rectangle
        Vector2 closestPosInChunck = new Vector2(Mathf.Clamp(pos.x, chunckPos.x, chunckPos.x + chunckSize), Mathf.Clamp(pos.y, chunckPos.y, chunckPos.y + chunckSize));

        // Calculate the distance between the circle's center and this closest point
        Vector2 brushToPoint = pos - closestPosInChunck;

        return brushToPoint.sqrMagnitude < radius * radius;
    }

#if UNITY_EDITOR
    private void OnDrawGizmos()
    {
        if (Application.isEditor)
        {
            Vector3 cameraPosition = SceneView.lastActiveSceneView.camera.transform.position;
            foreach (var chunk in AlleChunkObjekte)
            {
                chunk.SetLOD(cameraPosition);
            }
        }

        if(false)
        if (ActiveChunks != null)
        foreach(var p in ActiveChunks)
        {
            Gizmos.DrawWireCube(new Vector3(p.x + basisChunkGroese / 2f, 0, p.y + basisChunkGroese / 2f), Vector3.one * basisChunkGroese);
        }
    }
#endif
}

public struct ChunkData
{
    public bool isEmpty;
    public Vector2Int pos;
    public NativeArray<ChunkPixel> Data;
    public FixedList32Bytes<int> VerwendeteGrassorten;

    public ChunkData(Vector2Int pos)
    {
        isEmpty = false;
        this.pos = pos;
        Data = new NativeArray<ChunkPixel>(256, Allocator.Persistent);
        VerwendeteGrassorten = new FixedList32Bytes<int>();
    }
}

public struct ChunkPixel
{
    byte p1, p2, p3, p4;

    public byte this[int index]
    {
        get => index switch
        {
            0 => p1,
            1 => p2,
            2 => p3,
            3 => p4,
            _ => throw new IndexOutOfRangeException()
        };
        set => _ = index switch
        {
            0 => (p1 = value),
            1 => (p2 = value),
            2 => (p3 = value),
            3 => (p4 = value),
            _ => throw new IndexOutOfRangeException()
        };
    }
}