using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using Godot;
using Godot.Collections;
using Priority_Queue;

public class World : Spatial {
    public enum GenerationState {
        Undefined,
        Heightmap,
        TileType,
        Objects,
        Done
    }

    // constants
    public const int ChunkSize = 14;
    public const int NumChunkRows = 3;
    public const int NumChunkColumns = NumChunkRows;
    private static readonly Color RockColor = new(0.5f, 0.5f, 0.4f);
    private static readonly Color GrassColor = new(0, 0.4f, 0);
    private static readonly Color DarkGrassColor = new(0.05882353f, 0.5411765f, 0.05882353f);
    private static readonly Color LightWaterColor = new(0.05882353f, 0.05882353f, 0.8627451f);

    private readonly Godot.Collections.Dictionary<Vector2, WorldChunk> _cachedWorldChunks;
    private readonly List<Vector2> _addedChunkIndices = new();
    private readonly List<WorldChunk> _deactivatedWorldChunks = new();
    private readonly Image _heightmapImage = new();
    private readonly List<Vector2> _removedChunkIndices = new();
    private readonly Image _tileTypeMapImage = new();

    // referenced scenes
    private readonly PackedScene _worldChunkScene = GD.Load<PackedScene>("res://scenes/WorldChunk.tscn");

    private List<Vector2> _activeChunkIndices = new();
    private Rect2 _centerChunkRect;
    private readonly List<Spatial> _removedSpatialNodes = new();

    // delegate void OnCoordClicked(Vector2 world_pos);

    // other members
    private Vector2 _centerPlaneCoord;
    private Vector2 _chunkIndexNorthEast;
    private Vector2 _chunkIndexSouthWest;
    private Array<Spatial> _grassAssets;
    private ImageTexture _heightmapTexture;

    private OpenSimplexNoise _noiseGenerator = new();
    private Array<Spatial> _rockAssets;
    private MultiMeshInstance _tileMultiMeshInstance;
    private int _usedTileMeshInstances;
    private Array<Spatial> _treeAssets;
    private ImageTexture _viewTileTypeTexture;
    public Vector2 CenterChunkIndex = Vector2.Zero;
    public Spatial Chunks;
    public Color DebugColor;
    public HexGrid HexGrid = new();
    public int Seed = 0;

    public GenerationState State = GenerationState.Done;
    public Vector2 WorldTextureCoordinateOffset;


    // ui elements

    // scene nodes

    // resources

    // exports
    // [Export] public Vector2 Size = new Vector2(1, 1);

    // signals
    [Signal]
    private delegate void OnTilesChanged(Array<Vector2> removedChunkIndices, Array<Vector2> addedChunkIndices);

    [Signal]
    private delegate void OnWorldViewTileTypeImageChanged(Image viewTileTypeImage);

    [Signal]
    private delegate void OnHeightmapImageChanged(Image heightmapImage);

    [Signal]
    public delegate void EntityClicked(Entity entity);

    // signals
    [Signal]
    private delegate void TileClicked(HexTile3D tile3d);

    [Signal]
    private delegate void TileHovered(HexTile3D tile3d);

    public World() {
        Debug.Assert(ChunkSize % 2 == 0);

        _cachedWorldChunks = new Godot.Collections.Dictionary<Vector2, WorldChunk>();
    }

    // Called when the node enters the scene tree for the first time.
    public override void _Ready() {
        Chunks = (Spatial)FindNode("Chunks");
        Debug.Assert(Chunks != null);

        _tileMultiMeshInstance = (MultiMeshInstance)FindNode("TileMultiMeshInstance");
        Debug.Assert(_tileMultiMeshInstance != null);
        _tileMultiMeshInstance.Multimesh.InstanceCount =
            ChunkSize * ChunkSize * NumChunkColumns * NumChunkRows;
        _usedTileMeshInstances = 0;

        InitNoiseGenerator();

        GetNode<Spatial>("Assets").Visible = false;

        _rockAssets = new Array<Spatial>();
        foreach (Spatial asset in GetNode<Node>("Assets/Rocks").GetChildren()) {
            _rockAssets.Add(asset);
        }

        _grassAssets = new Array<Spatial>();
        foreach (Spatial asset in GetNode<Node>("Assets/Grass").GetChildren()) {
            _grassAssets.Add(asset);
        }

        _treeAssets = new Array<Spatial>();
        foreach (Spatial asset in GetNode<Node>("Assets/Trees").GetChildren()) {
            _treeAssets.Add(asset);
        }

        SetCenterPlaneCoord(Vector2.Zero);
    }

    public void InitNoiseGenerator() {
        _noiseGenerator = new OpenSimplexNoise();

        _noiseGenerator.Seed = Seed;
        _noiseGenerator.Octaves = 1;
        _noiseGenerator.Period = 10;
        _noiseGenerator.Persistence = 0.5f;
        _noiseGenerator.Lacunarity = 2;
    }

    public WorldChunk GetOrCreateWorldChunk(Vector2 chunkIndex, Color debugColor) {
        WorldChunk chunk;

        if (IsChunkCached(chunkIndex)) {
            return _cachedWorldChunks[chunkIndex];
        }

        if (_deactivatedWorldChunks.Count > 0) {
            chunk = _deactivatedWorldChunks.First();
            _deactivatedWorldChunks.RemoveAt(0);
        } else {
            chunk = CreateWorldChunk(chunkIndex, debugColor);
        }

        _cachedWorldChunks[chunkIndex] = chunk;

        return chunk;
    }

    private bool IsChunkCached(Vector2 chunkIndex) {
        return _cachedWorldChunks.ContainsKey(chunkIndex);
    }


    private WorldChunk CreateWorldChunk(Vector2 chunkIndex, Color debugColor) {
        WorldChunk result = (WorldChunk)_worldChunkScene.Instance();
        Chunks.AddChild(result);
        result.Connect("TileClicked", this, nameof(OnTileClicked));
        result.Connect("TileHovered", this, nameof(OnTileHovered));

        result.SetSize(ChunkSize);
        result.InitializeTileInstances(chunkIndex, _tileMultiMeshInstance, _usedTileMeshInstances);
        _usedTileMeshInstances += result.Tiles.GetChildCount();

        result.SetChunkIndex(chunkIndex, HexGrid);
        result.UpdateTileTransforms();

        result.DebugColor = debugColor;
        result.DebugColor.a = 0.6f;

        _cachedWorldChunks.Add(chunkIndex, result);

        return result;
    }

    private bool IsColorEqualApprox(Color colorA, Color colorB) {
        Vector3 colorDifference = new(colorA.r - colorB.r, colorA.g - colorB.g, colorA.b - colorB.b);
        return colorDifference.LengthSquared() < 0.1 * 0.1;
    }

    private Spatial SelectAsset(Vector2 textureCoord, Array<Spatial> assets, Random randomGenerator,
        double probability) {
        if (randomGenerator.NextDouble() < 1.0 - probability) {
            return null;
        }

        int assetIndex = randomGenerator.Next(assets.Count);
        Spatial assetInstance = (Spatial)assets[assetIndex].Duplicate();
        Transform assetTransform = Transform.Identity;
        assetTransform.origin = HexGrid.GetHexCenterVec3FromOffset(textureCoord);
        // TODO: assetTransform.origin.y = GetHeightAtOffset(offsetCoord);
        assetTransform.origin.y = 0;
        assetTransform.basis =
            assetTransform.basis.Rotated(Vector3.Up, (float)(randomGenerator.NextDouble() * Mathf.Pi * 2));
        assetInstance.Transform = assetTransform;

        return assetInstance;
    }

    private void PopulateChunk(WorldChunk chunk) {
        Random environmentRandom = new(Seed);

        chunk.CreateUnlockedTileTypeImage();

        foreach (int textureCoordU in Enumerable.Range(0, chunk.Size)) {
            foreach (int textureCoordV in Enumerable.Range(0, chunk.Size)) {
                Color colorValue = chunk.TileTypeImage.GetPixel(textureCoordU, textureCoordV);
                Vector2 textureCoord = new(textureCoordU, textureCoordV);
                Vector2 offsetCoord = chunk.ChunkIndex * ChunkSize + textureCoord;

                if (IsColorEqualApprox(colorValue, RockColor)) {
                    Spatial rockAsset = SelectAsset(textureCoord, _rockAssets, environmentRandom, 0.15);
                    if (rockAsset != null) {
                        chunk.Entities.AddChild(rockAsset);
                        MarkCellUnwalkable(HexGrid.GetHexAtOffset(offsetCoord));
                    }
                } else if (IsColorEqualApprox(colorValue, GrassColor) ||
                           IsColorEqualApprox(colorValue, DarkGrassColor)) {
                    Spatial grassAsset = SelectAsset(textureCoord, _grassAssets, environmentRandom, 0.15);
                    if (grassAsset != null) {
                        chunk.Entities.AddChild(grassAsset);
                    }

                    Tree treeAsset = SelectAsset(textureCoord, _treeAssets, environmentRandom, 0.05) as Tree;
                    if (treeAsset != null) {
                        chunk.Entities.AddChild(treeAsset);
                        treeAsset.Connect("EntityClicked", this, nameof(OnEntityClicked));
                        treeAsset.Connect("TreeChopped", this, nameof(OnBlockingSpatialRemoved));
                        MarkCellUnwalkable(HexGrid.GetHexAtOffset(offsetCoord));
                    }

                    // TODO: MarkCellUnwalkable(cell);
                    //                else if (environmentRandom.NextDouble() < 0.01)
//                {
//                    var chestAsset = (Chest)_chestScene.Instance();
//                    var assetTransform = Transform.Identity;
//                    assetTransform.origin = GetHexCenterFromOffset(offsetCoord);
//                    assetTransform.origin.y = GetHeightAtOffset(offsetCoord);
//                    chestAsset.Transform = assetTransform;
//                    Entities.AddChild(chestAsset);
//                    MarkCellUnwalkable(cell);
//                }
                }
//            else if (IsColorWater(colorValue))
//            {
//                MarkCellUnwalkable(cell);
//            }
            }
        }
    }

    public Vector2 WorldToOffsetCoords(Vector3 fromPositionWorld) {
        return HexGrid.GetHexAt(new Vector2(fromPositionWorld.x, fromPositionWorld.z)).OffsetCoords;
    }

    public Vector3 GetHexCenterFromOffset(Vector2 fromPositionOffset) {
        return HexGrid.GetHexCenterVec3FromOffset(fromPositionOffset);
    }

    public void UpdateCenterChunkFromPlaneCoord(Vector2 planeCoord) {
        if (State != GenerationState.Done) {
            GD.PrintErr("Cannot update chunk to new planeCoord " + planeCoord + ": Chunk generation not yet finished!");
            return;
        }

        // mark all chunks as retired
        Godot.Collections.Dictionary<Vector2, WorldChunk> oldCachedChunks = new(_cachedWorldChunks);

        // set new center chunk
        CenterChunkIndex = GetChunkTupleFromPlaneCoord(planeCoord);

        WorldChunk currentChunk = GetOrCreateWorldChunk(CenterChunkIndex,
            new Color(GD.Randf(), GD.Randf(), GD.Randf()));


        _centerChunkRect = new Rect2(
            new Vector2(currentChunk.Transform.origin.x, currentChunk.Transform.origin.z)
            + currentChunk.PlaneRect.Position,
            currentChunk.PlaneRect.Size);
        GD.Print("Center Chunk Rect: " + _centerChunkRect.Position + " size: " + _centerChunkRect.Size);

        // load or create adjacent chunks
        _activeChunkIndices = new List<Vector2>();
        _activeChunkIndices.Add(CenterChunkIndex + new Vector2(-1, -1));
        _activeChunkIndices.Add(CenterChunkIndex + new Vector2(0, -1));
        _activeChunkIndices.Add(CenterChunkIndex + new Vector2(1, -1));

        _activeChunkIndices.Add(CenterChunkIndex + new Vector2(-1, 0));
        _activeChunkIndices.Add(CenterChunkIndex);
        _activeChunkIndices.Add(CenterChunkIndex + new Vector2(+1, 0));

        _activeChunkIndices.Add(CenterChunkIndex + new Vector2(-1, +1));
        _activeChunkIndices.Add(CenterChunkIndex + new Vector2(0, +1));
        _activeChunkIndices.Add(CenterChunkIndex + new Vector2(+1, +1));

        // clear unused chunks
        _deactivatedWorldChunks.Clear();
        _addedChunkIndices.Clear();

        foreach (Vector2 oldChunkIndex in oldCachedChunks.Keys) {
            if (!_activeChunkIndices.Contains(oldChunkIndex)) {
                DeactivateChunk(oldCachedChunks[oldChunkIndex]);
            }
        }

        foreach (Vector2 activeChunkIndex in _activeChunkIndices) {
            WorldChunk chunk = GetOrCreateWorldChunk(activeChunkIndex,
                new Color(GD.Randf(), GD.Randf(), GD.Randf()));
            _cachedWorldChunks[activeChunkIndex] = chunk;
        }

        Debug.Assert(_activeChunkIndices.Count == NumChunkRows * NumChunkColumns);

        foreach (Vector2 chunkKey in _activeChunkIndices) {
            if (!oldCachedChunks.ContainsKey(chunkKey)) {
                ActivateChunk(_cachedWorldChunks[chunkKey], chunkKey);
                State = GenerationState.Heightmap;
            }
        }
    }

    private void ActivateChunk(WorldChunk chunk, Vector2 chunkIndex) {
        chunk.SetChunkIndex(chunkIndex, HexGrid);
        chunk.UpdateTileTransforms();

        _addedChunkIndices.Add(chunk.ChunkIndex);
        GenerateChunkNoiseMap(chunk);
    }

    private void DeactivateChunk(WorldChunk chunk) {
        _cachedWorldChunks.Remove(chunk.ChunkIndex);
        chunk.ClearContent();
        _deactivatedWorldChunks.Add(chunk);
    }

    private void GenerateChunkNoiseMap(WorldChunk chunk) {
        Vector2 chunkIndex = chunk.ChunkIndex;

        ImageTexture noiseImageTexture = new();
        noiseImageTexture.CreateFromImage(_noiseGenerator.GetImage(ChunkSize, ChunkSize, chunkIndex * ChunkSize),
            0);

        chunk.SetNoisemap(noiseImageTexture);
    }

    private void RemoveChunk(Vector2 cachedChunkKey) {
        _cachedWorldChunks.Remove(cachedChunkKey);
        _removedChunkIndices.Add(cachedChunkKey);

        foreach (WorldChunk chunk in Chunks.GetChildren()) {
            if (chunk.ChunkIndex == new Vector2(cachedChunkKey.x, cachedChunkKey.y)) {
                chunk.QueueFree();
            }
        }
    }


    private Vector2 GetChunkTupleFromPlaneCoord(Vector2 planeCoord) {
        HexCell hexCell = HexGrid.GetHexAt(planeCoord);
        return GetChunkIndexFromOffsetCoord(hexCell.OffsetCoords);
    }

    private Vector2 GetChunkIndexFromOffsetCoord(Vector2 offsetCoord) {
        return (offsetCoord / ChunkSize).Floor();
    }

    public void SetCenterPlaneCoord(Vector2 centerPlaneCoord) {
        if (!_centerChunkRect.HasPoint(centerPlaneCoord)) {
            UpdateCenterChunkFromPlaneCoord(centerPlaneCoord);

            UpdateChunkBounds();

            UpdateNavigationBounds();
        }
    }

    private void UpdateWorldViewTexture() {
        int worldChunkSize = ChunkSize;
        int numWorldChunkRows = NumChunkRows;
        int numWorldChunkColumns = NumChunkColumns;

        _heightmapImage.Create(worldChunkSize * numWorldChunkColumns, worldChunkSize * numWorldChunkRows, false,
            Image.Format.Rgba8);
        _tileTypeMapImage.Create(worldChunkSize * numWorldChunkColumns, worldChunkSize * numWorldChunkRows, false,
            Image.Format.Rgba8);

        foreach (Vector2 chunkIndex in _activeChunkIndices) {
            WorldChunk worldChunk = GetOrCreateWorldChunk(chunkIndex, Colors.White);

            _heightmapImage.BlendRect(
                worldChunk.HeightmapOffscreenViewport.GetTexture().GetData(),
                new Rect2(Vector2.Zero, Vector2.One * worldChunkSize),
                (chunkIndex - CenterChunkIndex + Vector2.One) * worldChunkSize);

            _tileTypeMapImage.BlendRect(
                worldChunk.TileTypeOffscreenViewport.GetTexture().GetData(),
                new Rect2(Vector2.Zero, Vector2.One * worldChunkSize),
                (chunkIndex - CenterChunkIndex + Vector2.One) * worldChunkSize);
        }

        _heightmapTexture = new ImageTexture();
        _heightmapTexture.CreateFromImage(_heightmapImage);

        _viewTileTypeTexture = new ImageTexture();
        _viewTileTypeTexture.CreateFromImage(_tileTypeMapImage);

        WorldTextureCoordinateOffset = _chunkIndexSouthWest * worldChunkSize;

        EmitSignal("OnWorldViewTileTypeImageChanged", _tileTypeMapImage);
        EmitSignal("OnHeightmapImageChanged", _heightmapImage);
    }

    private void UpdateChunkBounds() {
        _chunkIndexSouthWest = Vector2.Inf;
        _chunkIndexNorthEast = -Vector2.Inf;

        foreach (Vector2 chunkIndex in _activeChunkIndices) {
            if (chunkIndex.x <= _chunkIndexSouthWest.x && chunkIndex.y <= _chunkIndexSouthWest.y) {
                _chunkIndexSouthWest = chunkIndex;
            } else if (chunkIndex.x >= _chunkIndexNorthEast.x && chunkIndex.y >= _chunkIndexNorthEast.y) {
                _chunkIndexNorthEast = chunkIndex;
            }
        }
    }

    private void UpdateNavigationBounds() {
        HexCell cellSouthWest = HexGrid.GetHexAtOffset(_chunkIndexSouthWest * ChunkSize);
        HexGrid.SetBoundsOffset(cellSouthWest, ChunkSize * new Vector2(NumChunkColumns, NumChunkRows));
    }

    public void MarkCellUnwalkable(HexCell cell) {
        HexGrid.AddObstacle(cell);
    }

    public float GetHexCost(Entity entity, HexCell cell) {
        float nextHexCost = HexGrid.GetHexCost(cell);
        if (nextHexCost != 0) {
            Vector2 nextOffset = cell.OffsetCoords;
            Vector2 chunkIndex = GetChunkIndexFromOffsetCoord(nextOffset);
            WorldChunk chunk = _cachedWorldChunks[chunkIndex];
            Vector2 textureCoordinate = nextOffset - Vector2.One * ChunkSize * chunkIndex;

            Color tileTypeColor = chunk.TileTypeImage.GetPixel((int)textureCoordinate.x, (int)textureCoordinate.y);
            if (!IsColorEqualApprox(tileTypeColor, GrassColor) &&
                !IsColorEqualApprox(tileTypeColor, DarkGrassColor)) {
                nextHexCost = 0;
            }
        }

        return nextHexCost;
    }

    public float GetMoveCost(Entity entity, HexCell currentHex, HexCell nextHex) {
        if (GetHexCost(entity, nextHex) == 0) {
            return 0;
        }

        return HexGrid.GetMoveCost(currentHex.AxialCoords,
            new HexCell(nextHex.AxialCoords - currentHex.AxialCoords).CubeCoords);
    }

    public List<HexCell> FindPath(Entity entity, HexCell startHex, HexCell goalHex) {
        if (State != GenerationState.Done) {
            return new List<HexCell>();
        }

        Vector2 goalAxialCoords = goalHex.AxialCoords;

        SimplePriorityQueue<Vector2, float> frontier = new();
        frontier.Enqueue(startHex.AxialCoords, 0);
        System.Collections.Generic.Dictionary<Vector2, Vector2> cameFrom = new();
        System.Collections.Generic.Dictionary<Vector2, float> costSoFar = new();

        cameFrom.Add(startHex.AxialCoords, startHex.AxialCoords);
        costSoFar.Add(startHex.AxialCoords, 0);

        int FindPathCheckedCellCount = 0;

        while (frontier.Any()) {
            FindPathCheckedCellCount++;
            HexCell currentHex = new(frontier.Dequeue());
            Vector2 currentAxial = currentHex.AxialCoords;

            if (currentHex == goalHex) {
                break;
            }

            foreach (HexCell nextHex in currentHex.GetAllAdjacent()) {
                Vector2 nextAxial = nextHex.AxialCoords;

                float moveCost = GetMoveCost(entity, currentHex, nextHex);

                if (nextHex == goalHex && moveCost == 0 && GetHexCost(entity, nextHex) == 0) {
                    // Goal ist an obstacle
                    cameFrom[nextHex.AxialCoords] = currentHex.AxialCoords;
                    frontier.Clear();
                    break;
                }

                if (moveCost == 0) {
                    continue;
                }

                moveCost += costSoFar[currentHex.AxialCoords];
                if (!costSoFar.ContainsKey(nextHex.AxialCoords) || moveCost < costSoFar[nextHex.AxialCoords]) {
                    costSoFar[nextHex.AxialCoords] = moveCost;
                    float priority = moveCost + nextHex.DistanceTo(goalHex);

                    frontier.Enqueue(nextHex.AxialCoords, priority);
                    cameFrom[nextHex.AxialCoords] = currentHex.AxialCoords;
                }
            }
        }

        // GD.Print("Checked Cell Count: " + FindPathCheckedCellCount);

        List<HexCell> result = new();
        if (!cameFrom.ContainsKey(goalHex.AxialCoords)) {
            GD.Print("Failed to find path from " + startHex + " to " + goalHex);
            return result;
        }

        if (HexGrid.GetHexCost(goalAxialCoords) != 0) {
            result.Add(goalHex);
        }

        HexCell pathHex = goalHex;
        while (pathHex != startHex) {
            pathHex = new HexCell(cameFrom[pathHex.AxialCoords]);
            result.Insert(0, pathHex);
        }

        return result;
    }

    public override void _Process(float delta) {
        GenerationState oldState = State;

        UpdateGenerationState();

        if (oldState != GenerationState.Done && State == GenerationState.Done) {
            UpdateWorldViewTexture();
        }

        while (_removedSpatialNodes.Count > 0) {
            GD.Print("Queueing deletion of " + _removedSpatialNodes[0]);
            _removedSpatialNodes[0].QueueFree();
            _removedSpatialNodes.RemoveAt(0);
        }
    }

    private void UpdateGenerationState() {
        if (State == GenerationState.Heightmap) {
            int numChunksGeneratingHeightmap = 0;
            foreach (Vector2 chunkIndex in _addedChunkIndices) {
                WorldChunk chunk = _cachedWorldChunks[chunkIndex];
                if (chunk.HeightMapFrameCount > 0) {
                    numChunksGeneratingHeightmap++;
                }
            }

            if (numChunksGeneratingHeightmap == 0) {
                // assign height map images
                foreach (Vector2 chunkIndex in _addedChunkIndices) {
                    WorldChunk chunk = _cachedWorldChunks[chunkIndex];
                    chunk.SetHeightmap(chunk.HeightmapOffscreenViewport.GetTexture());
                }

                State = GenerationState.TileType;
            }
        } else if (State == GenerationState.TileType) {
            int numChunksGeneratingTileType = 0;
            foreach (Vector2 chunkIndex in _addedChunkIndices) {
                WorldChunk chunk = _cachedWorldChunks[chunkIndex];
                if (chunk.TileTypeMapFrameCount > 0) {
                    numChunksGeneratingTileType++;
                }
            }

            if (numChunksGeneratingTileType == 0) {
                State = GenerationState.Objects;
            }
        } else if (State == GenerationState.Objects) {
            // generate objects
            foreach (Vector2 chunkIndex in _addedChunkIndices) {
                PopulateChunk(_cachedWorldChunks[chunkIndex]);
            }

            _addedChunkIndices.Clear();

            State = GenerationState.Done;
        }
    }

    private void OnEntityClicked(Entity entity) {
        EmitSignal("EntityClicked", entity);
    }

    public void OnTileClicked(HexTile3D tile) {
        EmitSignal("TileClicked", tile);
    }

    public void OnTileHovered(HexTile3D tile) {
        EmitSignal("TileHovered", tile);
    }

    public void OnBlockingSpatialRemoved(Spatial spatialNode) {
        if (spatialNode.IsQueuedForDeletion()) {
            return;
        }

        HexGrid.RemoveObstacle(HexGrid.GetHexAt(new Vector2(spatialNode.GlobalTranslation.x,
            spatialNode.GlobalTranslation.z)));
        _removedSpatialNodes.Add(spatialNode);
    }
}