using System;
using System.Runtime.InteropServices;


namespace VideoStatusInspectorCSLib
{
    /// <summary>
    /// 图像读入时的模式
    /// </summary>
    public enum EnumImreadMode
    {
        Unchanged = -1,
        Grayscale = 0,
        Color = 1,
        AnyDepth = 2,
        AnyColor = 4,
        LoadGdal = 8,
    }

    /// <summary>
    /// 图像信息
    /// </summary>
    public struct StructImageInfo
    {
        private int _width;
        private int _height;
        private EnumColorType _colorType;
        private IntPtr _dataPointer;

        public int Width
        {
            get => _width;
            set => _width = value;
        }
        public int Height
        {
            get => _height;
            set => _height = value;
        }
        public EnumColorType ColorType
        {
            get => _colorType;
            set => _colorType = value;
        }
        public IntPtr DataPointer
        {
            get => _dataPointer;
            set => _dataPointer = value;
        }
        public StructImageInfo(int width, int height, EnumColorType colorType, IntPtr dataPointer)
        {
            _width = width;
            _height = height;
            _colorType = colorType;
            _dataPointer = dataPointer;
        }

    }

    public class ImageDecode
    {
        [DllImport(@"VideoStatusInspector")]
        [return: MarshalAs(UnmanagedType.I1)]
        internal static extern bool ImgDataDecode(byte[] srcImData, int srcDataSize, EnumImreadMode imreadMode, ref StructImageInfo imageInfo);

        [DllImport(@"VideoStatusInspector")]
        internal static extern int GetDecodedImgSize(byte[] srcImData, int srcDataSize, EnumImreadMode imreadMode);

        private const EnumImreadMode _imreadMode = EnumImreadMode.Unchanged;
        private byte[] _decodedBytes = new byte[0];
        private string _errorMsg;

        public RawImage DecodeOneImage(byte[] bytes)
        {
            try
            {
                var decodedByteCounts = GetDecodedImgSize(bytes, bytes.Length, _imreadMode);
                if (_decodedBytes.Length < decodedByteCounts)
                {
                    Array.Resize(ref _decodedBytes, decodedByteCounts);
                }
                IntPtr dataPointer = Marshal.UnsafeAddrOfPinnedArrayElement(_decodedBytes, 0);
                StructImageInfo imageInfo = new StructImageInfo(0, 0, EnumColorType.Bgr, dataPointer);
                if (!ImgDataDecode(bytes, bytes.Length, _imreadMode, ref imageInfo))
                {
                    _errorMsg = "Failed at ImgDataDecode.";
                    return null;
                }
                return new RawImage(_decodedBytes, imageInfo.Width, imageInfo.Height, imageInfo.ColorType);
            }
            catch (Exception excep)
            {
                _errorMsg = "Failed at DecodeOneImage: "+ excep.Message;
                return null;
            }
        }

        public string GetErrorMsg()
        {
            return _errorMsg;
        }

    }
}