// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.

using System;
using System.Linq;
using System.Numerics;

using SixLabors.ImageSharp.Formats.Jpeg.Components;
using SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.PixelFormats;

namespace SixLabors.ImageSharp.Tests.Formats.Jpg.Utils
{
    internal static partial class LibJpegTools
    {
        /// <summary>
        /// Stores spectral blocks for jpeg components.
        /// </summary>
        public class ComponentData : IEquatable<ComponentData>, IJpegComponent
        {
            public ComponentData(int widthInBlocks, int heightInBlocks, int index)
            {
                this.HeightInBlocks = heightInBlocks;
                this.WidthInBlocks = widthInBlocks;
                this.Index = index;
                this.SpectralBlocks = Configuration.Default.MemoryAllocator.Allocate2D<Block8x8>(this.WidthInBlocks, this.HeightInBlocks);
            }

            public Size Size => new Size(this.WidthInBlocks, this.HeightInBlocks);

            public int Index { get; }

            public Size SizeInBlocks => new Size(this.WidthInBlocks, this.HeightInBlocks);

            public Size SamplingFactors => throw new NotSupportedException();

            public Size SubSamplingDivisors => throw new NotSupportedException();

            public int HeightInBlocks { get; }

            public int WidthInBlocks { get; }

            public int QuantizationTableIndex => throw new NotSupportedException();

            public Buffer2D<Block8x8> SpectralBlocks { get; private set; }

            public short MinVal { get; private set; } = short.MaxValue;

            public short MaxVal { get; private set; } = short.MinValue;

            internal void MakeBlock(short[] data, int y, int x)
            {
                this.MinVal = Math.Min(this.MinVal, data.Min());
                this.MaxVal = Math.Max(this.MaxVal, data.Max());
                this.SpectralBlocks[x, y] = new Block8x8(data);
            }

            public static ComponentData Load(JpegComponent c, int index)
            {
                var result = new ComponentData(
                    c.WidthInBlocks,
                    c.HeightInBlocks,
                    index);

                for (int y = 0; y < result.HeightInBlocks; y++)
                {
                    Span<Block8x8> blockRow = c.SpectralBlocks.GetRowSpan(y);
                    for (int x = 0; x < result.WidthInBlocks; x++)
                    {
                        short[] data = blockRow[x].ToArray();
                        result.MakeBlock(data, y, x);
                    }
                }

                return result;
            }

            public Image<Rgba32> CreateGrayScaleImage()
            {
                var result = new Image<Rgba32>(this.WidthInBlocks * 8, this.HeightInBlocks * 8);

                for (int by = 0; by < this.HeightInBlocks; by++)
                {
                    for (int bx = 0; bx < this.WidthInBlocks; bx++)
                    {
                        this.WriteToImage(bx, by, result);
                    }
                }

                return result;
            }

            internal void WriteToImage(int bx, int by, Image<Rgba32> image)
            {
                Block8x8 block = this.SpectralBlocks[bx, by];

                for (int y = 0; y < 8; y++)
                {
                    for (int x = 0; x < 8; x++)
                    {
                        float val = this.GetBlockValue(block, x, y);

                        var v = new Vector4(val, val, val, 1);
                        Rgba32 color = default;
                        color.FromVector4(v);

                        int yy = (by * 8) + y;
                        int xx = (bx * 8) + x;
                        image[xx, yy] = color;
                    }
                }
            }

            internal float GetBlockValue(Block8x8 block, int x, int y)
            {
                float d = this.MaxVal - this.MinVal;
                float val = block[y, x];
                val -= this.MinVal;
                val /= d;
                return val;
            }

            public bool Equals(ComponentData other)
            {
                if (other is null)
                {
                    return false;
                }

                if (ReferenceEquals(this, other))
                {
                    return true;
                }

                bool ok = this.Index == other.Index && this.HeightInBlocks == other.HeightInBlocks
                          && this.WidthInBlocks == other.WidthInBlocks;
                if (!ok)
                {
                    return false;
                }

                for (int y = 0; y < this.HeightInBlocks; y++)
                {
                    for (int x = 0; x < this.WidthInBlocks; x++)
                    {
                        Block8x8 a = this.SpectralBlocks[x, y];
                        Block8x8 b = other.SpectralBlocks[x, y];
                        if (!a.Equals(b))
                        {
                            return false;
                        }
                    }
                }

                return true;
            }

            public override bool Equals(object obj)
            {
                if (obj is null)
                {
                    return false;
                }

                if (object.ReferenceEquals(this, obj))
                {
                    return true;
                }

                if (obj.GetType() != this.GetType())
                {
                    return false;
                }

                return this.Equals((ComponentData)obj);
            }

            public override int GetHashCode()
            {
                return HashCode.Combine(this.Index, this.HeightInBlocks, this.WidthInBlocks, this.MinVal, this.MaxVal);
            }

            public ref Block8x8 GetBlockReference(int column, int row)
            {
                throw new NotImplementedException();
            }

            public static bool operator ==(ComponentData left, ComponentData right)
            {
                return object.Equals(left, right);
            }

            public static bool operator !=(ComponentData left, ComponentData right)
            {
                return !object.Equals(left, right);
            }
        }
    }
}