using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Windows.Forms;

namespace Steganography
{
	public partial class Form1 : Form
	{
		private const int encodingBitMask = ~3;
		private const int decodingBitMask = 3;
		private const int bitMaskA = 3;
		private const int bitMaskB = 3 << 2;
		private const int bitMaskG = 3 << 4;
		private const int bitMaskR = 3 << 6;

		private string imagePath = "";
		private string textToHide = "";

		private Bitmap image;
		private Bitmap encodedImage;

		private bool fileHideSet; // False by default
		private bool fileEncodeSet;

		public Form1()
		{
			InitializeComponent();
			// Add event handlers
			btnFileHide.Click += btnFileHide_Click;
			btnFileEncode.Click += btnFileEncode_Click;

			ofdFileEncode.Filter = @"Image Files (PNG)|*.PNG";
		}

		private static bool isValidPath(string path)
		{
			if (path == "")
			{
				MessageBox.Show(@"Please provide an image path.");
				return false;
			}

			if (!File.Exists(path))
			{
				MessageBox.Show(@"Couldn't find the file");
				return false;
			}

			string ext = Path.GetExtension(path);

			if (ext == null || ext.ToLower() != ".png")
			{
				MessageBox.Show(@"Sorry, this only works with images with alpha channels. I.e. PNGs");
				return false;
			}

			return true;
		}

		private static Color encode(Color pixel, char c)
		{
			int r = (c & bitMaskR) >> 6;
			int g = (c & bitMaskG) >> 4;
			int b = (c & bitMaskB) >> 2;
			int a = (c & bitMaskA);

			int red   = (pixel.R & encodingBitMask) | r;
			int green = (pixel.G & encodingBitMask) | g;
			int blue  = (pixel.B & encodingBitMask) | b;
			int alpha = (pixel.A & encodingBitMask) | a;

			return Color.FromArgb(alpha, red, green, blue);
		}

		private static char decode(Color pixel)
		{
			int red   = pixel.R & decodingBitMask;
			int green = pixel.G & decodingBitMask;
			int blue  = pixel.B & decodingBitMask;
			int alpha = pixel.A & decodingBitMask;

			return (char)((red << 6) | (green << 4) | (blue << 2) | alpha);
		}

		private void btnHideText_Click(object sender, EventArgs e)
		{
			imagePath  = tbImagePath.Text;
			textToHide = tbTextToAdd.Text;

			if (!isValidPath(imagePath))
				return;

			// Open the image
			image = new Bitmap(imagePath);

			encodedImage = new Bitmap(image.Width, image.Height);

			int charCounter = 0;

			for (int x = 0; x < image.Width; x++)
			{
				for (int y = 0; y < image.Height; y++)
				{
					// Store current character in least significant bits of current pixel's components
					Color currentPixel = image.GetPixel(x, y);

					encodedImage.SetPixel(x, y, encode(currentPixel, textToHide[charCounter]));

					charCounter = charCounter == textToHide.Length - 1 ? 0 : charCounter + 1;
				}
			}
			image.Dispose();
			string saveName = Path.ChangeExtension(imagePath, null) + "_encoded.png";
			encodedImage.Save(saveName, ImageFormat.Png);
			encodedImage.Dispose();
			MessageBox.Show(@"Saved new image successfully");
		}

		private void btnReadText_Click(object sender, EventArgs e)
		{
			imagePath = tbImagePath.Text;
			if (!isValidPath(imagePath))
				return;

			// Open the image
			image = new Bitmap(imagePath);

			string str = "";

			int maxChars = 16;
			for (int i = 0; i < maxChars; i++)
			{
				Color currentPixel = image.GetPixel(i / image.Width, i % image.Width);

				str += decode(currentPixel);
			}
			image.Dispose();
			MessageBox.Show(@"This image contains the message: " + str + @" (first 16 characters).");
		}

		// Select File To Hide Inside The Other File
		private void btnFileHide_Click(object sender, EventArgs e)
		{
			if (ofdFileToHide.ShowDialog() != DialogResult.OK) return;
			fileHideSet = true;
		}

		// Select File To Hide The Other File Inside Of
		// Or to read an already hidden file from
		private void btnFileEncode_Click(object sender, EventArgs e)
		{
			if (ofdFileEncode.ShowDialog() != DialogResult.OK) return;
			fileEncodeSet = true;
		}

		// TODO: Test this
		// TODO: Hide file type and length within encoded image
		private void btnEncode_Click(object sender, EventArgs e)
		{
			if (!fileHideSet)
			{
				MessageBox.Show(@"You must select a file to hide");
				return;
			}

			if (!fileEncodeSet)
			{
				MessageBox.Show(@"You must select an image to hide the file in");
				return;
			}

			if (Path.GetExtension(ofdFileEncode.FileName) != ".png")
			{
				MessageBox.Show(@"You must hide your file in a png image");
				return;
			}

			var fileHideInfo   = new FileInfo(ofdFileToHide.FileName);
			var fileEncodeInfo = new FileInfo(ofdFileEncode.FileName);

			if (fileHideInfo.Length > fileEncodeInfo.Length)
			{
				MessageBox.Show(@"The file you are trying to hide must be smaller than the one you are trying to hide it in");
				return;
			}

			image = new Bitmap(ofdFileEncode.FileName);
			encodedImage = new Bitmap(image.Width, image.Height);
			StreamReader sr = new StreamReader(ofdFileToHide.FileName);
			int charCounter = 0;

			for (int x = 0; x < image.Width; x++)
			{
				for (int y = 0; y < image.Height; y++)
				{
					Color currentPixel = image.GetPixel(x, y);
					char[] currentChar = new char[1];
					sr.Read(currentChar, charCounter, 1);
					encodedImage.SetPixel(x, y, encode(currentPixel, currentChar[0]));
					charCounter = charCounter == fileHideInfo.Length - 1 ? 0 : charCounter + 1;
				}
			}

			sr.Close();
			image.Dispose();

			string saveName = Path.ChangeExtension(ofdFileEncode.FileName, null) + "_encoded.png";
			encodedImage.Save(saveName, ImageFormat.Png);
			encodedImage.Dispose();
			MessageBox.Show(@"Saved new image successfully");
		}

		private void btnDecode_Click(object sender, EventArgs e)
		{

		}
	}
}