using Sarand.Net.Standard.Base.App;
using Sarand.Net.Standard.Base.Core;
using Sarand.Net.Standard.Base.Helpers;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Advanced;
using SixLabors.ImageSharp.Formats;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace Sarand.Net.Standard.Base.Utils
{
	//=======================================================================
	// Image handling methods utilising SixLabors ImageSharp package.
	//=======================================================================
	public static class ImageUtils
	{
		//-------------------------------------------------------------------
		private static readonly String className = typeof(ImageUtils).ToString();

		//-------------------------------------------------------------------
		public class ImageConfig
		{
			public byte[] ImageData { get; set; }
			public string ImageFormatName;
			public string DefaultMimeType;
			public Sacs.MimeType MimeType;
			public bool ValidImage { get; set; }
			public int Width { get; set; }
			public int Height { get; set; }
		}

		//-------------------------------------------------------------------
		public static bool IsSvg(byte[] imageData)
		{
			try
			{
				if (!imageData.Contains((byte)'<')) return false;
				String imageText = Encoding.UTF8.GetString(imageData);
				if (!imageText.ContainsCI("<svg")) return false;
				if (!imageText.ContainsCI(" xmlns=\"http://www.w3.org/2000/svg\"")) return false;
				return true;
			}
			catch (Exception) { }
			return false;
		}

		//-------------------------------------------------------------------
		/// <summary>
		/// Convert the data stream to an image and extract width and height.
		/// </summary>
		/// <param name="imageData"></param>
		/// <returns>Flag to indicate whether interpretation of image data succeeded.</returns>
		public static ImageConfig VerifyImageData(byte[] imageData)
		{
			ImageConfig imageConfig = new ImageConfig();
			imageConfig.ImageData = imageData;
			try
			{
				IImageFormat imageFormat = null;
				using (var image = LoadImage(imageData, out imageFormat))
				{
					if (image == null) return imageConfig;
					imageConfig.ImageFormatName = imageFormat.Name;
					imageConfig.DefaultMimeType = imageFormat.DefaultMimeType;
					imageConfig.MimeType = EnumUtil.ParseEnum(imageConfig.ImageFormatName, Sacs.MimeType.Unknown);
					imageConfig.Width = image.Width;
					imageConfig.Height = image.Height;
				}
				imageConfig.ValidImage = true;
			}
			catch (Exception exc)
			{
				SaLogger.Warn($"{SysUtil.Fn} {ExceptionUtil.GetLogMessage(exc)}");
			}
			return imageConfig;
		}

		//-------------------------------------------------------------------
		/// <summary>
		/// Convert the SVG data stream to an image and extract width and height.
		/// </summary>
		/// <param name="imageData"></param>
		/// <returns>Flag to indicate whether interpretation of image data succeeded.</returns>
		public static ImageConfig VerifySvgImageData(byte[] imageData)
		{
			ImageConfig imageConfig = new ImageConfig();
			imageConfig.ImageData = imageData;
			imageConfig.ImageFormatName = "svg";
			imageConfig.DefaultMimeType = "svg";
			imageConfig.MimeType = EnumUtil.ParseEnum(imageConfig.ImageFormatName, Sacs.MimeType.Unknown);
			imageConfig.Width = 0;
			imageConfig.Height = 0;
			imageConfig.ValidImage = true;
			return imageConfig;
		}

		//-------------------------------------------------------------------
		// Load from byte array.
		/// <summary>Convert the data stream to an image.</summary>
		public static SixLabors.ImageSharp.Image LoadImage(byte[] imageData)
		{
			var image = Image.Load<Rgba32>(imageData);
			return image;
		}
		/// <summary>
		/// Convert the data stream to an image.
		/// <para>Identify the image's format on load.</para>
		/// </summary>
		public static SixLabors.ImageSharp.Image LoadImage(byte[] imageData, out IImageFormat format)
		{
			var image = Image.Load<Rgba32>(imageData);
			format = Image.DetectFormat(imageData);
			return image;
		}

		//-------------------------------------------------------------------
		// Convert to byte array.
		/// <summary>Convert the data stream to an image.</summary>
		public static Byte[] GetImageData(this SixLabors.ImageSharp.Image image, IImageFormat imageFormat)
		{
			using (MemoryStream ms = new MemoryStream())
			{
				var imageEncoder = image.Configuration.ImageFormatsManager.GetEncoder(imageFormat);
				image.Save(ms, imageEncoder);
				return ms.ToArray();
			}
		}

		//-------------------------------------------------------------------
		/// <summary>
		/// Resize the image with the specified limits, if required.
		/// </summary>
		/// <param name="config">Image data</param>
		/// <param name="widthMax"></param>
		/// <param name="heightMax"></param>
		/// <returns>Flag to indicate whether operation was successful.</returns>
		public static bool ConstrainImage(ImageConfig config, ushort widthMax, ushort heightMax)
		{
			if (config.Width == 0 || config.Height == 0) return true;
			if (widthMax < 1 || heightMax < 1) return false;
			if (config.Width <= widthMax && config.Height <= heightMax) return true;
			config.ValidImage = false;

			try
			{
				// Resize the image.
				IImageFormat imageFormat = null;
				using (var image = LoadImage(config.ImageData, out imageFormat))
				{
					double resizeProportion = Math.Min(widthMax / (double)image.Width, heightMax / (double)image.Height);
					image.Mutate(img => img.Resize((int)(image.Width * resizeProportion), (int)(image.Height * resizeProportion)));
					config.ImageData = image.GetImageData(imageFormat);
					config.Width = image.Width;
					config.Height = image.Height;
					config.ValidImage = true;
				}
			}
			catch (Exception exc)
			{
				SaLogger.Warn($"{SysUtil.Fn} {ExceptionUtil.GetLogMessage(exc)}");
			}

			return config.ValidImage;
		}

		//-------------------------------------------------------------------
	}
	//=======================================================================
}