using System.Text;
using DotNext;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Formats.Jpeg;
using SixLabors.ImageSharp.PixelFormats;

namespace Common;

/// <summary>
/// 图像处理工具
/// </summary>
public class Image
{
    /// <summary>
    /// 将 RGB565 格式转换为 RGB24 格式
    /// RGB565: 5位红色 + 6位绿色 + 5位蓝色 = 16位 (2字节)
    /// RGB24: 8位红色 + 8位绿色 + 8位蓝色 = 24位 (3字节)
    /// </summary>
    /// <param name="rgb565Data">RGB565格式的原始数据</param>
    /// <param name="width">图像宽度</param>
    /// <param name="height">图像高度</param>
    /// <param name="isLittleEndian">是否为小端序（默认为true）</param>
    /// <returns>RGB24格式的转换后数据</returns>
    public static Result<byte[]> ConvertRGB565ToRGB24(byte[] rgb565Data, int width, int height, bool isLittleEndian = true)
    {
        if (rgb565Data == null)
            return new(new ArgumentNullException(nameof(rgb565Data)));

        if (width <= 0 || height <= 0)
            return new(new ArgumentException("Width and height must be positive"));

        // 计算像素数量
        var expectedPixelCount = width * height;
        var actualPixelCount = rgb565Data.Length / 2;

        if (actualPixelCount < expectedPixelCount)
        {
            return new(new ArgumentException(
                $"RGB565 data length insufficient. Expected: {expectedPixelCount * 2} bytes, Actual: {rgb565Data.Length} bytes"));
        }

        try
        {
            var pixelCount = Math.Min(actualPixelCount, expectedPixelCount);
            var rgb24Data = new byte[pixelCount * 3];

            for (int i = 0; i < pixelCount; i++)
            {
                // 读取 RGB565 数据
                var rgb565Index = i * 2;
                if (rgb565Index + 1 >= rgb565Data.Length) break;

                // 组合成16位值
                UInt16 rgb565;
                if (isLittleEndian)
                {
                    rgb565 = (UInt16)(rgb565Data[rgb565Index] | (rgb565Data[rgb565Index + 1] << 8));
                }
                else
                {
                    rgb565 = (UInt16)((rgb565Data[rgb565Index] << 8) | rgb565Data[rgb565Index + 1]);
                }

                // 提取各颜色分量
                var r5 = (rgb565 >> 11) & 0x1F;  // 高5位为红色
                var g6 = (rgb565 >> 5) & 0x3F;   // 中间6位为绿色
                var b5 = rgb565 & 0x1F;          // 低5位为蓝色

                // 转换为8位颜色值
                var r8 = (byte)((r5 * 255) / 31);  // 5位扩展到8位
                var g8 = (byte)((g6 * 255) / 63);  // 6位扩展到8位
                var b8 = (byte)((b5 * 255) / 31);  // 5位扩展到8位

                // 存储到 RGB24 数组
                var rgb24Index = (i%2 == 0)?((i+1) * 3):((i-1) * 3);
                rgb24Data[rgb24Index] = r8;     // R
                rgb24Data[rgb24Index + 1] = g8; // G
                rgb24Data[rgb24Index + 2] = b8; // B
            }

            return rgb24Data;
        }
        catch (Exception ex)
        {
            return new(ex);
        }
    }

    /// <summary>
    /// 将 RGB24 格式转换为 RGB565 格式
    /// RGB24: 8位红色 + 8位绿色 + 8位蓝色 = 24位 (3字节)
    /// RGB565: 5位红色 + 6位绿色 + 5位蓝色 = 16位 (2字节)
    /// </summary>
    /// <param name="rgb24Data">RGB24格式的原始数据</param>
    /// <param name="width">图像宽度</param>
    /// <param name="height">图像高度</param>
    /// <param name="isLittleEndian">是否为小端序（默认为true）</param>
    /// <returns>RGB565格式的转换后数据</returns>
    public static Result<byte[]> ConvertRGB24ToRGB565(byte[] rgb24Data, int width, int height, bool isLittleEndian = true)
    {
        if (rgb24Data == null)
            return new(new ArgumentNullException(nameof(rgb24Data)));

        if (width <= 0 || height <= 0)
            return new(new ArgumentException("Width and height must be positive"));

        var expectedPixelCount = width * height;
        var actualPixelCount = rgb24Data.Length / 3;

        if (actualPixelCount < expectedPixelCount)
        {
            return new(new ArgumentException(
                $"RGB24 data length insufficient. Expected: {expectedPixelCount * 3} bytes, Actual: {rgb24Data.Length} bytes"));
        }

        try
        {
            var pixelCount = Math.Min(actualPixelCount, expectedPixelCount);
            var rgb565Data = new byte[pixelCount * 2];

            for (int i = 0; i < pixelCount; i++)
            {
                var rgb24Index = i * 3;
                if (rgb24Index + 2 >= rgb24Data.Length) break;

                // 读取 RGB24 数据
                var r8 = rgb24Data[rgb24Index];
                var g8 = rgb24Data[rgb24Index + 1];
                var b8 = rgb24Data[rgb24Index + 2];

                // 转换为5位、6位、5位
                var r5 = (UInt16)((r8 * 31) / 255);
                var g6 = (UInt16)((g8 * 63) / 255);
                var b5 = (UInt16)((b8 * 31) / 255);

                // 组合成16位值
                var rgb565 = (UInt16)((r5 << 11) | (g6 << 5) | b5);

                // 存储到 RGB565 数组
                var rgb565Index = i * 2;
                if (isLittleEndian)
                {
                    rgb565Data[rgb565Index] = (byte)(rgb565 & 0xFF);
                    rgb565Data[rgb565Index + 1] = (byte)(rgb565 >> 8);
                }
                else
                {
                    rgb565Data[rgb565Index] = (byte)(rgb565 >> 8);
                    rgb565Data[rgb565Index + 1] = (byte)(rgb565 & 0xFF);
                }
            }

            return rgb565Data;
        }
        catch (Exception ex)
        {
            return new(ex);
        }
    }

    /// <summary>
    /// 将 RGB24 数据转换为 JPEG 格式
    /// </summary>
    /// <param name="rgb24Data">RGB24格式的图像数据</param>
    /// <param name="width">图像宽度</param>
    /// <param name="height">图像高度</param>
    /// <param name="quality">JPEG质量（1-100，默认80）</param>
    /// <returns>JPEG格式的字节数组</returns>
    public static Result<byte[]> ConvertRGB24ToJpeg(byte[] rgb24Data, int width, int height, int quality = 80)
    {
        if (rgb24Data == null)
            return new(new ArgumentNullException(nameof(rgb24Data)));

        if (width <= 0 || height <= 0)
            return new(new ArgumentException("Width and height must be positive"));

        if (quality < 1 || quality > 100)
            return new(new ArgumentException("Quality must be between 1 and 100"));

        var expectedDataLength = width * height * 3;
        if (rgb24Data.Length < expectedDataLength)
        {
            return new(new ArgumentException(
                $"RGB24 data length insufficient. Expected: {expectedDataLength} bytes, Actual: {rgb24Data.Length} bytes"));
        }

        try
        {
            using var image = new SixLabors.ImageSharp.Image<Rgb24>(width, height);

            // 将 RGB 数据复制到 ImageSharp 图像
            for (int y = 0; y < height; y++)
            {
                for (int x = 0; x < width; x++)
                {
                    int index = (y * width + x) * 3;
                    if (index + 2 < rgb24Data.Length)
                    {
                        var pixel = new Rgb24(rgb24Data[index], rgb24Data[index + 1], rgb24Data[index + 2]);
                        image[x, y] = pixel;
                    }
                }
            }

            using var stream = new MemoryStream();
            image.SaveAsJpeg(stream, new JpegEncoder { Quality = quality });
            return stream.ToArray();
        }
        catch (Exception ex)
        {
            return new(ex);
        }
    }

    /// <summary>
    /// 将 RGB565 数据直接转换为 JPEG 格式
    /// </summary>
    /// <param name="rgb565Data">RGB565格式的图像数据</param>
    /// <param name="width">图像宽度</param>
    /// <param name="height">图像高度</param>
    /// <param name="quality">JPEG质量（1-100，默认80）</param>
    /// <param name="isLittleEndian">是否为小端序（默认为true）</param>
    /// <returns>JPEG格式的字节数组</returns>
    public static Result<byte[]> ConvertRGB565ToJpeg(byte[] rgb565Data, int width, int height, int quality = 80, bool isLittleEndian = true)
    {
        // 先转换为RGB24
        var rgb24Result = ConvertRGB565ToRGB24(rgb565Data, width, height, isLittleEndian);
        if (!rgb24Result.IsSuccessful)
        {
            return new(rgb24Result.Error);
        }

        // 再转换为JPEG
        return ConvertRGB24ToJpeg(rgb24Result.Value, width, height, quality);
    }

    /// <summary>
    /// 创建 MJPEG 帧头部
    /// </summary>
    /// <param name="frameDataLength">帧数据长度</param>
    /// <param name="boundary">边界字符串（默认为"--boundary"）</param>
    /// <returns>MJPEG帧头部字节数组</returns>
    public static byte[] CreateMjpegFrameHeader(int frameDataLength, string boundary = "--boundary")
    {
        var header = $"{boundary}\r\nContent-Type: image/jpeg\r\nContent-Length: {frameDataLength}\r\n\r\n";
        return Encoding.ASCII.GetBytes(header);
    }

    /// <summary>
    /// 创建 MJPEG 帧尾部
    /// </summary>
    /// <returns>MJPEG帧尾部字节数组</returns>
    public static byte[] CreateMjpegFrameFooter()
    {
        return Encoding.ASCII.GetBytes("\r\n");
    }

    /// <summary>
    /// 创建完整的 MJPEG 帧数据
    /// </summary>
    /// <param name="jpegData">JPEG数据</param>
    /// <param name="boundary">边界字符串（默认为"--boundary"）</param>
    /// <returns>完整的MJPEG帧数据</returns>
    public static Result<byte[]> CreateMjpegFrame(byte[] jpegData, string boundary = "--boundary")
    {
        if (jpegData == null)
            return new(new ArgumentNullException(nameof(jpegData)));

        try
        {
            var header = CreateMjpegFrameHeader(jpegData.Length, boundary);
            var footer = CreateMjpegFrameFooter();

            var totalLength = header.Length + jpegData.Length + footer.Length;
            var frameData = new byte[totalLength];

            var offset = 0;
            Array.Copy(header, 0, frameData, offset, header.Length);
            offset += header.Length;

            Array.Copy(jpegData, 0, frameData, offset, jpegData.Length);
            offset += jpegData.Length;

            Array.Copy(footer, 0, frameData, offset, footer.Length);

            return frameData;
        }
        catch (Exception ex)
        {
            return new(ex);
        }
    }

    /// <summary>
    /// 验证图像数据长度是否正确
    /// </summary>
    /// <param name="data">图像数据</param>
    /// <param name="width">图像宽度</param>
    /// <param name="height">图像高度</param>
    /// <param name="bytesPerPixel">每像素字节数</param>
    /// <returns>验证结果</returns>
    public static bool ValidateImageDataLength(byte[] data, int width, int height, int bytesPerPixel)
    {
        if (data == null || width <= 0 || height <= 0 || bytesPerPixel <= 0)
            return false;

        var expectedLength = width * height * bytesPerPixel;
        return data.Length >= expectedLength;
    }

    /// <summary>
    /// 获取图像格式信息
    /// </summary>
    /// <param name="format">图像格式枚举</param>
    /// <returns>格式信息</returns>
    public static ImageFormatInfo GetImageFormatInfo(ImageFormat format)
    {
        return format switch
        {
            ImageFormat.RGB565 => new ImageFormatInfo("RGB565", 2, "16-bit RGB format (5R+6G+5B)"),
            ImageFormat.RGB24 => new ImageFormatInfo("RGB24", 3, "24-bit RGB format (8R+8G+8B)"),
            ImageFormat.RGBA32 => new ImageFormatInfo("RGBA32", 4, "32-bit RGBA format (8R+8G+8B+8A)"),
            ImageFormat.Grayscale8 => new ImageFormatInfo("Grayscale8", 1, "8-bit grayscale format"),
            _ => new ImageFormatInfo("Unknown", 0, "Unknown image format")
        };
    }
}

/// <summary>
/// 图像格式枚举
/// </summary>
public enum ImageFormat
{
    /// <summary>
    /// RGB565
    /// </summary>
    RGB565,

    /// <summary>
    /// RGB888 / RGB24
    /// </summary>
    RGB24,

    /// <summary>
    /// RGBA8888 / RGBA32
    /// </summary>
    RGBA32,

    /// <summary>
    /// 灰度图
    /// </summary>
    Grayscale8
}

/// <summary>
/// 图像格式信息
/// </summary>
public record ImageFormatInfo(string Name, int BytesPerPixel, string Description);
