frmMain.cs

﻿using System;
using System.IO;
using System.Diagnostics;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using iText;
using iText.Kernel.Geom;
using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Canvas;
using iText.Kernel.Pdf.Xobject;
using Microsoft.VisualBasic;	// LOL

namespace PDFEncrypt
{
	

	public partial class frmMain : Form
	{
		const int PW_LENGTH_MIN = 12;	// Minimum generated password length
		const int PW_LENGTH_MAX = 24;   // Maximum generated password length
		const string PW_CHARS = "abcdefghijkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789";	// List of characters to be used in random passwords


		public frmMain()
		{
			InitializeComponent();
		}

		private void btnInputBrowse_Click(object sender, EventArgs e)
		{
			DialogResult result = dlgOpen.ShowDialog();
			if (result == DialogResult.Cancel) { return; }

			txtInputFile.Text = dlgOpen.FileName;

			// Generate output filename matching input with "-encrypted" if none is specified.
			if (txtOutputFile.Text == "")
			{
				txtOutputFile.Text = System.IO.Path.GetDirectoryName(txtInputFile.Text) + "\\";
				txtOutputFile.Text += System.IO.Path.GetFileNameWithoutExtension(txtInputFile.Text);
				txtOutputFile.Text += "-encrypted.pdf";	
			}
		}

		private void btnOutputBrowse_Click(object sender, EventArgs e)
		{
			DialogResult result = dlgSave.ShowDialog();
			if (result == DialogResult.Cancel) { return; }

			txtOutputFile.Text = dlgSave.FileName;
		}

		private void frmMain_Load(object sender, EventArgs e)
		{
			// Add listener for updated settings
			Settings.notify.Add(settingsChanged);

			// Load settings from registry
			Settings.load();			
		}

		private void settingsChanged()
		{
			// This function is executed when settings change.
			Console.WriteLine("Settings changed notification.");
		}

		private void btnClose_Click(object sender, EventArgs e)
		{
			// Close the app
			this.Close();
		}

		private void btnPasswordGenerate_Click(object sender, EventArgs e)
		{
			// Generate a random password
			var rnd = new System.Random();	// Random number generator
			int length = rnd.Next(PW_LENGTH_MIN, PW_LENGTH_MAX);	// Choose password length.
			string result = "";

			// Pick 'length' characters from the allowed characters.
			for(int i = 0; i<length; i++)
			{
				result += PW_CHARS[rnd.Next(0, PW_CHARS.Length - 1)].ToString();
			}

			// Set password
			txtPassword.Text = result;

			// Copy to clipboard
			btnCopy_Click(sender, e);
		}

		private void btnCopy_Click(object sender, EventArgs e)
		{
			// Copy password to clipboard.
			txtPassword.Focus();
			txtPassword.SelectAll();
			Clipboard.SetText(txtPassword.Text);

			// Show Copied label
			lblCopied.Visible = true;
		}

		private void txtPassword_TextChanged(object sender, EventArgs e)
		{
			// Hide Copied label
			lblCopied.Visible = false;

		}

		private void txtPassword_KeyDown(object sender, KeyEventArgs e)
		{
			// Hide Copied label
			lblCopied.Visible = false;

		}

		private void btnEncrypt_Click(object sender, EventArgs e)
		{
			// Clean up text
			txtInputFile.Text = txtInputFile.Text.Trim();
			txtOutputFile.Text = txtOutputFile.Text.Trim();

			// Ensure input and output are not the same.
			if (txtInputFile.Text.ToLower() == txtOutputFile.Text.ToLower())
			{
				MessageBox.Show("Source and Destination files cannot be the same.", "Invalid source/destination", MessageBoxButtons.OK, MessageBoxIcon.Error);
				txtOutputFile.Focus();
				txtOutputFile.SelectAll();
				return;
			}

			// Ensure input file exists.
			if (!File.Exists(txtInputFile.Text))
			{
				MessageBox.Show("Source file does not exist.");
				txtInputFile.Focus();
				txtInputFile.SelectAll();
				return;
			}

			// If output file exists, prompt to overwrite.
			if (File.Exists(txtOutputFile.Text))
			{
				if(MessageBox.Show("Destination file already exists.  Overwrite this file?","Overwrite file?", MessageBoxButtons.YesNo) != DialogResult.Yes)
				{
					txtOutputFile.Focus();
					txtOutputFile.SelectAll();
					return;
				}
			}

			// Verify password:
			if (txtPassword.Text == "")
			{
				MessageBox.Show("No password specified.");
				txtPassword.Focus();
				return;
			}
			
			// Confirm password:
			if (Settings.password_confirm)
			{
				var input = new frmInputBox();
				input.prompt = "Please retype the password to confirm.";
				input.title = "Confirm password";
				input.ShowDialog();	// Modal, blocking call

				if (input.cancelled) { return;  }

				// If password doesn't match, stop.
				if (input.result != txtPassword.Text)
				{
					MessageBox.Show("Password does not match. Please retry.");
					return;
				}
			}

			// See https://itextpdf.com/en/resources/faq/technical-support/itext-7/how-protect-already-existing-pdf-password
			try
			{

				// Set mouse cursor to wait.
				Cursor.Current = Cursors.WaitCursor;
				Application.DoEvents();

				// Encryption properties:
				int encryption_properties = (int) Settings.encryption_type;
				
				// If specified, disable encrypting metadata.
				if (!Settings.encrypt_metadata)
				{
					encryption_properties |= EncryptionConstants.DO_NOT_ENCRYPT_METADATA;
				}

				// Set document options
				int document_options = 0;
				if (Settings.allow_printing)	{ document_options |= EncryptionConstants.ALLOW_PRINTING; }
				if (Settings.allow_degraded_printing) { document_options |= EncryptionConstants.ALLOW_DEGRADED_PRINTING; }
				if (Settings.allow_modifying) { document_options |= EncryptionConstants.ALLOW_MODIFY_CONTENTS; }
				if (Settings.allow_modifying_annotations) { document_options |= EncryptionConstants.ALLOW_MODIFY_ANNOTATIONS; }
				if (Settings.allow_copying) { document_options |= EncryptionConstants.ALLOW_COPY; }
				if (Settings.allow_form_fill) { document_options |= EncryptionConstants.ALLOW_FILL_IN; }
				if (Settings.allow_assembly) { document_options |= EncryptionConstants.ALLOW_ASSEMBLY; }
				if (Settings.allow_screenreaders) { document_options |= EncryptionConstants.ALLOW_SCREENREADERS; }

				PdfReader reader = new PdfReader(txtInputFile.Text);	// Create a PdfReader with the input file.
				WriterProperties prop = new WriterProperties();	// Set properties of output
				prop.SetStandardEncryption(Encoding.ASCII.GetBytes(txtPassword.Text), null, document_options, encryption_properties);  // Enable encryption
				// Setting Owner Password to null generates random password.

				PdfWriter writer = new PdfWriter(txtOutputFile.Text, prop);	// Set up the output file
				PdfDocument pdf = new PdfDocument(reader, writer);	// Create the new document
				pdf.Close();	// Close the output document.
			}
			catch (Exception ex)
			{
				MessageBox.Show("An error occurred while processing the file: " + ex.Message);
				Cursor.Current = Cursors.Default;
				return;
			}

			// If launching a program:
			if (Settings.run_after)
			{
				// Attempt to run the program, passing the newly encrypted filename.
				Process.Start(Settings.run_after_file, txtOutputFile.Text);
			}

			// If opening the output file:
			if (Settings.open_after)
			{
				// Attempt to launch the default app for the file.
				Process.Start(txtOutputFile.Text);
			}

			// If launching Explorer:
			if (Settings.show_folder_after)
			{
				// Attempt to launch the folder with the file highlighted.
				Process.Start("explorer.exe", "/select," + txtOutputFile.Text);
			}

			// If closing after encryption
			if (Settings.close_after)
			{
				this.Close();
			}

			Cursor.Current = Cursors.Default;	// Return to default cursor.
		}

		private void btnSettings_Click(object sender, EventArgs e)
		{
			var settings = new frmSettings();
			settings.ShowDialog();
		}
	}
}