using System;
using System.Collections.Generic;
using FOU.Scripts.Elements;
using Godot;

namespace FOU.Scripts;

public class Chunk {
    public Element[,] Elements;
    public int Index = -1;
    public Chunk NeighborN = null;
    public Chunk NeighborE = null;
    public Chunk NeighborS = null;
    public Chunk NeighborW = null;

    private readonly Image image;
    private readonly int sizeX;
    private readonly int sizeY;
    private readonly HashSet<Element> activeElements;
    private readonly HashSet<Element> toAddElements = new();
    private readonly HashSet<Element> toRemoveElements = new();

    public Chunk(int x, int y, int index) {
        Index = index;
        sizeX = x;
        sizeY = y;

        Elements = new Element[x, y];
        for (int i = 0; i < sizeX; i++) {
            for (int j = 0; j < sizeY; j++) {
                Elements[i,j] = new Element(i, j, this);
            }
        }

        activeElements = new HashSet<Element>(sizeX * sizeY);

        image = Image.CreateEmpty(sizeX, sizeY, false, Image.Format.Rgb8);
        image.Fill(Colors.Black);
    }

    public void Update() {
        foreach (Element e in activeElements)
            e.Update();

        // apply changes:
        if (toRemoveElements.Count > 0) {
            foreach (Element removeElement in toRemoveElements) {
                activeElements.Remove(removeElement);
                removeElement.ResetColor();
            }
            toRemoveElements.Clear();
        }

        if (toAddElements.Count > 0) {
            foreach (Element addElement in toAddElements) {
                activeElements.Add(addElement);
                addElement.SetDebugColor(Colors.Green);
            }
            toAddElements.Clear();
        }
    }

    public void SetElementActive(Element e, bool active) {
        if (e.GetType() == typeof(Element) && active) return;

        if (active) AddToChunk(e);
        else RemoveFromChunk(e);
    }

    public void WritePixel<T>(int x, int y, int size) {
        int halfsize = size/2;

        Type type = typeof(T);

        for (int i = -halfsize; i <= halfsize; i++) {
            for (int j = -halfsize; j <= halfsize; j++) {
                int X = Mathf.Clamp(x + i, 0, sizeX-1);
                int Y = Mathf.Clamp(y + j, 0, sizeY-1);
                object o = Activator.CreateInstance(type, X, Y, this);

                // check if not empty:
                if (Elements[X,Y].GetType() != typeof(Element)) {
                    return;
                }

                // if (Elements[X,Y].GetType() != type) {
                Elements[X, Y].Chunk.RemoveFromChunk(Elements[X, Y]);
                Elements[X, Y] = o as Element;
                Elements[X, Y].Active = true;
                // }
            }
        }
    }

    public int ActiveElementsCount() {
        return activeElements.Count;
    }

    public void Swap(Element what, Vector2I pos) {
        Swap(what, Get(pos));
    }

    public Element Get(Vector2I pos) {
        Element e = null;

        if (pos.Y < 0) {
            if (NeighborN != null)
                e = NeighborN.Get(pos.X, NeighborN.sizeY + pos.Y);

        } else if (pos.Y >= sizeY) {
            if (NeighborS != null)
                e = NeighborS.Get(pos.X, sizeY - pos.Y);

        } else if (pos.X < 0) {
            if (NeighborE != null)
                e = NeighborE.Get(NeighborE.sizeX + pos.X, pos.Y);

        } else if (pos.X >= sizeX) {
            if (NeighborW != null)
                e = NeighborW.Get(sizeX - pos.X, pos.Y);

        } else e = Get(pos.X, pos.Y);

        return e;
    }

    private Element Get(int x, int y) {
        if (x < 0 || x >= sizeX) return null;
        if (y < 0 || y >= sizeY) return null;

        return Elements[x,y];
    }

    public bool IsEmpty(Vector2I pos) {
        return Get(pos)?.GetType() == typeof(Element);
    }

    private void Swap(Element what, Element swapTo) {
        if (what == null || swapTo == null) {
            GD.PrintErr("Trying to swap null");
            return;
        }

        if (what.Chunk != swapTo.Chunk) {
            what.Chunk.RemoveFromChunk(what);
            swapTo.Chunk.AddToChunk(what);
        }

        Element temp = new Element(what);

        what.Position = swapTo.Position;
        what.Chunk = swapTo.Chunk;
        what.Chunk.Elements[what.Position.X, what.Position.Y] = what;

        swapTo.Position = temp.Position;
        swapTo.Chunk = temp.Chunk;
        swapTo.Chunk.Elements[swapTo.Position.X, swapTo.Position.Y] = swapTo;

        what.Active = true;
        swapTo.Active = true;
    }

    public override string ToString() {
        return $"Chunk {Index}";
    }

    private void RemoveFromChunk(Element e) {
        toRemoveElements.Add(e);
    }

    private void AddToChunk(Element e) {
        toAddElements.Add(e);
    }
}