using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Text;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.PixelFormats;

namespace RecrownedAthenaeum.Tools.TextureAtlas
{

    public class TexturePacker : IDisposable
    {
        private enum SupportedExtensions
        {
            jpeg, jpg, png
        }

        int powLimit;

        Rectangle theoreticalSpace;
        Node masterNode;
        ImageHandler[] imageHandlers;
        Queue<ImageHandler> imageHandlerQueue;
        int textureLength;

        /// <summary>
        /// Machine to pack multiple textures into one large texture.
        /// </summary>
        /// <param name="rootDirectoryPath">Path to textures.</param>
        /// <param name="powLimit">Power of two limit for auto expanding texture. Default is 12 which is a 4096x4096 texture.</param>
        /// <param name="startingPower">What power to start at and build up from. Default is 8 which is a 256x256 texture.</param>
        internal TexturePacker(string rootDirectoryPath, int powLimit = 12, int startingPower = 8)
        {
            this.powLimit = powLimit;
            string[] paths = Directory.GetFiles(rootDirectoryPath);
            int currentPoT = startingPower;
            List<ImageHandler> imageHandlers = new List<ImageHandler>();
            for (int pathID = 0; pathID < paths.Length; pathID++)
            {
                SupportedExtensions extension;
                if (Enum.TryParse(Path.GetExtension(paths[pathID]), out extension))
                {
                    ImageHandler image = new ImageHandler(paths[pathID]);
                    imageHandlers.Add(image);
                }
            }
            imageHandlers.Sort();
            this.imageHandlers = imageHandlers.ToArray();
            imageHandlerQueue = new Queue<ImageHandler>(imageHandlers);
            textureLength = currentPoT;
        }

        /// <summary>
        /// Builds a texture atlas.
        /// </summary>
        /// <param name="AutoCorrectAtlasSize">Whether or not to automatically upscale atlas' texture in the case it is too small. Goes up to 4096 by default.</param>
        public void Build(bool AutoCorrectAtlasSize = true)
        {
            masterNode = new Node();
            masterNode.region.Width = textureLength;
            masterNode.region.Height = textureLength;

            ImageHandler imageHandler;
            while (imageHandlerQueue.TryDequeue(out imageHandler))
            {
                try
                {
                    masterNode.InsertImageHandler(imageHandler);
                }
                catch (InvalidOperationException)
                {
                    textureLength *= 2;
                    if (!AutoCorrectAtlasSize || textureLength > Math.Pow(2, powLimit))
                    {
                        throw new InvalidOperationException("Dimensions of texture goes past limit amount of " + powLimit + " which is " + Math.Pow(2, powLimit) + ". New texture size would be " + textureLength + "x" + textureLength + ".");
                    }
                    Build();
                }
            }
        }

        /// <summary>
        /// Renders the build into a PNG file and generates the respective <see cref="TextureAtlasData"/> meant for serialization and later to be loaded.
        /// </summary>
        public void Save()
        {

        }

        public void Dispose()
        {
            foreach (ImageHandler imageHandler in imageHandlers)
            {
                imageHandler.Dispose();
            }
        }

        private class Node
        {
            public Node parent;
            private Node a, b;
            public Node childA { get { if (a == null) a = new Node(this); return a; } set { value.parent = this; a = value; } }
            public Node childB { get { if (b == null) { b = new Node(this); } return b; } set { value.parent = this; b = value; } }
            public Rectangle region;
            public ImageHandler imageHandler;
            public bool Filled { get { return (imageHandler != null) || (a != null && b != null && a.Filled && b.Filled); } }

            public Node(Node parent = null)
            {
                this.parent = parent;
                region = parent.region;
            }

            public void SetNodeRegion(int x, int y, int width, int height, ImageHandler imageHandler)
            {
                region.X = x;
                region.Y = y;
                region.Width = width;
                region.Height = height;
                this.imageHandler = imageHandler;
            }

            public void SetNodeRegion(ImageHandler imageHandler)
            {
                SetNodeRegion(imageHandler.x, imageHandler.y, imageHandler.Width, imageHandler.Height, imageHandler);
            }


            public Node InsertImageHandler(ImageHandler imageHandler)
            {
                if (imageHandler.Width != region.Width)
                {
                    if (imageHandler.Width < region.Width)
                    {
                        if (a == null)
                        {
                            childA.region.Width = imageHandler.Width;
                            childB.region.Width = region.Width - childA.region.Width;
                        }
                        if (!childA.Filled && imageHandler.Width <= childA.region.Width)
                        {
                            return childA.InsertImageHandler(imageHandler);
                        }

                        if (!childB.Filled)
                        {
                            return childB.InsertImageHandler(imageHandler);
                        }
                    }
                }
                else if (imageHandler.Height != region.Height)
                {
                    if (imageHandler.Height < region.Height)
                    {
                        if (a == null)
                        {
                            childA.region.Height = imageHandler.Height;
                            childB.region.Height = region.Height - childA.region.Height;
                        }

                        if (!childA.Filled && imageHandler.Width <= childA.region.Width)
                        {
                            return childA.InsertImageHandler(imageHandler);
                        }

                        if (!childB.Filled)
                        {
                            return childB.InsertImageHandler(imageHandler);
                        }
                    }
                }
                else
                {
                    imageHandler.x = region.X;
                    imageHandler.y = region.Y;
                    this.imageHandler = imageHandler;
                    return this;
                }

                throw new ArgumentException();
            }
        }

        private class ImageHandler : IComparable<ImageHandler>, IDisposable
        {
            public readonly string path;
            public readonly Image<Rgba32> image;
            public int Area { get { return image.Width * image.Height; } }
            public string Name { get { return Path.GetFileName(path); } }
            public int Width { get { return image.Width; } }
            public int Height { get { return image.Height; } }
            public int x, y;

            internal ImageHandler(String path)
            {
                this.path = path;
                using (FileStream stream = new FileStream(path, FileMode.Open))
                {
                    image = Image.Load(stream);
                }
            }

            public int CompareTo(ImageHandler tImage)
            {
                return Area - tImage.Area;
            }

            public void Dispose()
            {
                image.Dispose();
            }
        }
    }
}