using System.Collections.Generic;
using System.Drawing;
using System.IO;
using Syroot.BinaryData;
using Syroot.Worms.Core;
using Syroot.Worms.Core.IO;

namespace Syroot.Worms.Mgame
{
    /// <summary>
    /// Represents an IGD image container.
    /// </summary>
    public class Igd : ILoadableFile
    {
        // ---- CONSTRUCTORS & DESTRUCTOR ------------------------------------------------------------------------------

        /// <summary>
        /// Initializes a new instance of the <see cref="Igd"/> class, loading data from the file with the given
        /// <paramref name="fileName"/>.
        /// </summary>
        /// <param name="fileName">The name of the file to load the data from.</param>
        public Igd(string fileName) => Load(fileName);

        /// <summary>
        /// Initializes a new instance of the <see cref="Igd"/> class, loading data from the given
        /// <paramref name="stream"/>.
        /// </summary>
        /// <param name="stream">The <see cref="Stream"/> to load the data from.</param>
        public Igd(Stream stream) => Load(stream);

        // ---- PROPERTIES ---------------------------------------------------------------------------------------------

        public int UnknownA { get; set; }
        public int UnknownB { get; set; }
        public byte[] UnknownC { get; set; }
        public Point Center { get; set; }
        public Size Size { get; set; }
        public IList<IgdImage> Images { get; set; }

        // ---- METHODS (PUBLIC) ---------------------------------------------------------------------------------------

        /// <inheritdoc/>
        public void Load(string fileName)
        {
            using FileStream stream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
            Load(stream);
        }

        /// <inheritdoc/>
        public void Load(Stream stream)
        {
            UnknownA = stream.ReadInt32();
            UnknownB = stream.ReadInt32();
            UnknownC = stream.ReadBytes(8);
            Center = new Point(stream.ReadInt32(), stream.ReadInt32());
            Size = new Size(stream.ReadInt32(), stream.ReadInt32());

            // Load the palette.
            int colorCount = stream.ReadInt32();
            Color[] palette = new Color[colorCount];
            for (int i = 0; i < colorCount; i++)
            {
                palette[i] = Color.FromArgb(stream.Read1Byte(), stream.Read1Byte(), stream.Read1Byte());
                stream.Seek(1); // Ignore empty alpha.
            }

            // Load the images.
            int imageCount = stream.ReadInt32();
            Images = new List<IgdImage>(imageCount);
            for (int i = 0; i < imageCount; i++)
            {
                IgdImage image = new IgdImage();
                image.UnknownA = stream.ReadInt32();
                int index = stream.ReadInt32();
                if (index != i)
                    throw new InvalidDataException("Read index does not match image index.");
                image.UnknownB = stream.ReadInt32();
                image.UnknownC = stream.ReadInt32();
                image.Size = new Size(stream.ReadInt32(), stream.ReadInt32());
                image.Center = new Point(stream.ReadInt32(), stream.ReadInt32());

                // Decompress the data.
                int dataSize = stream.ReadInt32();
                int dataSizeCompressed = stream.ReadInt32();
                image.RawBitmap = new RawBitmap
                {
                    Size = new Size(Algebra.NextMultiple(image.Size.Width, 4), image.Size.Height),
                    Palette = palette,
                    Data = Decompress(stream, dataSizeCompressed, dataSize)
                };
                Images.Add(image);
            }
        }

        // ---- METHODS (PRIVATE) --------------------------------------------------------------------------------------

        private static byte[] Decompress(Stream stream, int compressedSize, int decompressedSize)
        {
            // Each input byte is either a byte of decompressed data or a marker for a following command (0xFF).
            // A command consists of 4 bytes which specify the range of bytes to copy from already decompressed data.
            byte[] decompressed = new byte[decompressedSize];
            int i = 0;

            long endPosition = stream.Position + compressedSize - 2;
            while (stream.Position < endPosition)
            {
                byte b = stream.Read1Byte();
                if (b == 0xFF)
                {
                    // Copy existing data.
                    byte mask1 = stream.Read1Byte();
                    byte mask2 = stream.Read1Byte();
                    int offset = mask2 & 0x0FFF | ((mask1 & 0x000F) << 8);
                    int bytesToCopy = stream.Read1Byte();
                    for (int j = 0; j < bytesToCopy; j++)
                    {
                        int outIndex = i + j;
                        decompressed[outIndex] = decompressed[outIndex - offset];
                    }
                    i += bytesToCopy;
                }
                else
                {
                    // Raw transfer next byte.
                    decompressed[i++] = b;
                }
            }

            // Validate remaining 2 check bytes and return the decompressed data if valid.
            if (stream.ReadUInt16() != 0x0080)
                throw new InvalidDataException("Invalid check bytes at end of compressed image data.");
            return decompressed;
        }
    }
}