/*
  This shows some of the details involved in a GUI application that uses
  Botan. Actually most of the code is just dealing with GTK+, but it shows how
  the password callback and pulse function stuff works. (See gtk_ui.cpp for the
  acutal password callback code.)

  The major points of interest (assuming what you care about is how to use
  Botan from a GUI, and not looking at my terrible GTK code) are gtk_ui.cpp
  and, in this file, GTK_Pulse, gen_key(), and get_key():

     gtk_ui.cpp and get_key() show how to get a passphrase from a user for
     decrypting (well, in theory, anything), but in this case, PKCS #8 private
     keys. Which is coincidentally the only thing Botan currently uses UI
     objects for, though that will probably change eventually. GTK_UI does
     double duty, for getting passphrases for encryption as well (in
     do_save_key).

     gen_key() and GTK_Pulse show how to do an activity meter while doing a
     long-term operation inside Botan. Since, typically, the only operations
     which take a long time and can't be broken up into smaller parts are prime
     generation/testing, that is currently where the pulse hooks are
     called. It's certainly not the most general callback method in the world,
     but it's general enough that it's usable without getting in the way too
     much. The callbacks will eventually be extended to other parts of the
     library (Pipe, maybe) where it's useful.

  This program is in the public domain.
*/
#include <fstream>
#include <iostream>
#include <memory>

#include <botan/botan.h>
#include <botan/libstate.h>
#include <botan/look_pk.h>
#include <botan/filters.h>
#include <botan/dsa.h>
// we don't have a 'using namespace' here, so it's easy to grep for code that
// is actually dealing with the library (rather than messing around with GTK).

#include <gtk/gtk.h>
#include "gtk_ui.h"

/*************************************************
* Pop up an message box                          *
*************************************************/
static void show_dialog(const std::string& about_message,
                        const std::string& dialog_name)
   {
   GtkDialogFlags flags =
      (GtkDialogFlags)(GTK_DIALOG_DESTROY_WITH_PARENT | GTK_DIALOG_MODAL);

   GtkWidget* dialog = gtk_dialog_new_with_buttons(dialog_name.c_str(),
                                                   NULL, flags,
                                                   GTK_STOCK_OK,
                                                   GTK_RESPONSE_NONE,
                                                   NULL);
   GtkWidget* label = gtk_label_new(NULL);
   gtk_label_set_markup(GTK_LABEL(label), about_message.c_str());
   gtk_label_set_justify(GTK_LABEL(label), GTK_JUSTIFY_CENTER);

   g_signal_connect_swapped(GTK_OBJECT(dialog), "response",
                            G_CALLBACK(gtk_widget_destroy),
                            GTK_OBJECT(dialog));

   gtk_container_add(GTK_CONTAINER(GTK_DIALOG(dialog)->vbox), label);
   gtk_widget_show_all(dialog);
   }

/*************************************************
* Pop up an About box                            *
*************************************************/
static void show_about()
   {
   const std::string about_message =
      "<big>DSA Utility</big>\n"
      "\n"
      "A simple application showing how to use Botan within a GUI.\n"
      "It lets you generate or load keys, and sign text files.\n"
      "\n"
      "Send comments/questions to <tt>lloyd@randombit.net</tt>";

   show_dialog(about_message, "About");
   }

/*************************************************
* Pop up a help box                              *
*************************************************/
static void show_help()
   {
   const std::string help_message =
      "<big>DSA Utility Help</big>\n"
      "\n"
      "Simply, this is a (very) simple text editor, with the added ability\n"
      "of being able to generate or read a DSA private key, and sign the\n"
      "text buffer using that key.\n"
      "\n"
      "You can load, edit, and save text files as you would normally. If a\n"
      "key is loaded (done using the commands in the Keys menu), you can\n"
      "also use the Sign command (in the Signing menu) to generate a\n"
      "signature for the current file. It will be displayed at the bottom\n"
      "of the screen (if it has been calculated for the current buffer\n"
      "contents), and can be saved using the \"Save Sig\" command.\n"
      "\n"
      "Signatures generated by this program can be verified using a the\n"
      "<tt>dsa_ver</tt> example included in the Botan distribution.\n";

   show_dialog(help_message, "Help");
   }

/*************************************************
* Get and return a filename from the user        *
*************************************************/
static std::string get_filename(const std::string& title)
   {
   GtkWidget* dialog = gtk_file_selection_new(title.c_str());

   /* Some window managers don't display the titles of transient windows,
      put a message elsewhere for those people.
   */
   GtkWidget* label = gtk_label_new(title.c_str());
   gtk_container_add(GTK_CONTAINER(GTK_DIALOG(dialog)->vbox), label);

   std::string fsname;

   gtk_widget_show(label); /* dialog_run won't show sub-widgets */
   if(gtk_dialog_run(GTK_DIALOG(dialog)) == GTK_RESPONSE_OK)
      fsname = gtk_file_selection_get_filename(GTK_FILE_SELECTION(dialog));
   gtk_widget_destroy(dialog);

   /* If it's a directory, that's no good */
   if(fsname.size() && fsname[fsname.size()-1] == '/')
      return "";

   return fsname;
   }

/*************************************************
* Global state                                   *
*************************************************/
static Botan::DSA_PrivateKey* key = 0; // our key
static GtkTextBuffer* buffer = 0; // the text buffer
static std::string buffer_source;
  // what file (if any) the buffer's data came from
static GtkWidget* sig_view = 0; // the signature

/*************************************************
* Zap the currently set signature (if any)       *
*************************************************/
static void zap_sig()
   {
   gtk_editable_delete_text(GTK_EDITABLE(sig_view), 0, -1);
   }

/*************************************************
* Save the current key                           *
*************************************************/
static void do_save_key(const std::string& title)
   {
   if(key == 0)
      return;

   std::string filename = get_filename(title.c_str());

   if(filename != "")
      {
      const std::string msg = "Select a passphrase to encrypt the key:";

      std::ofstream out_priv(filename.c_str());

      GTK_UI ui;
      Botan::User_Interface::UI_Result result;
      std::string passphrase = ui.get_passphrase(msg, result);

      if(result == Botan::User_Interface::OK)
         out_priv << Botan::PKCS8::PEM_encode(*key, passphrase);
      else
         out_priv << Botan::PKCS8::PEM_encode(*key);

      // for testing
      //std::cout << X509::PEM_encode(*key);
      }
   }

/*************************************************
* Generate a signature for the text buffer       *
*************************************************/
static void sign_buffer()
   {
   /* No key? Ignore request. */
   if(key == 0)
      return;

   /* same format as the text-mode dsa_sign example */
   Botan::Pipe pipe(new Botan::PK_Signer_Filter(
                       Botan::get_pk_signer(*key, "EMSA1(SHA-1)")
                       ),
                    new Botan::Base64_Encoder
      );

   /* It would probably be smart to do this a little bit at a time */
   GtkTextIter start, end;
   gtk_text_buffer_get_bounds(buffer, &start, &end);
   gchar* bits = gtk_text_buffer_get_text(buffer, &start, &end, FALSE);
   size_t length = strlen(bits);

   pipe.start_msg();
   pipe.write((unsigned char*)bits, length);
   pipe.end_msg();

   std::string sig = pipe.read_all_as_string();

   zap_sig();

   gint position = 0;
   gtk_editable_insert_text(GTK_EDITABLE(sig_view), sig.c_str(), sig.length(),
                            &position);

   g_free(bits);
   }

/*************************************************
* GTK+ pulse callback                            *
*************************************************/
class GTK_Pulse : public Botan::Library_State::UI
   {
   public:
      void pulse(Botan::Pulse_Type);
   };

void GTK_Pulse::pulse(Botan::Pulse_Type)
   {
   /* We need this to flush the updates, otherwise GTK+ will wait until we're
   done with the computation before doing any updates (generally the right
   thing, but not with a progress bar).
   */

   while(gtk_events_pending())
      gtk_main_iteration();
   }

/*************************************************
* Actual do the pulse (as a GTK+ timeout func)   *
*************************************************/
static gboolean gtk_pulse_timeout(void* pbar)
   {
   GtkWidget* progress_bar = (GtkWidget*)pbar;
   gtk_progress_bar_pulse(GTK_PROGRESS_BAR(progress_bar));
   return TRUE; /* keep calling us */
   }

/*************************************************
* Generate a new key                             *
*************************************************/
static void gen_key()
   {
   /* This gives a nice smooth progress bar, though we do use up quite a bit of
      CPU for it. Keep in mind that if PULSE_INTERVAL is significantly less
      than the average time between pulses from the library, the progress bar
      will jerk around going slower or faster. Keep it at at least 50ms.
   */
   const double PROGRESS_PER_PULSE = .01; /* % of bar */
   const guint32 PULSE_INTERVAL = 30; /* ms */

   delete key;

   GtkDialogFlags flags =
      (GtkDialogFlags)(GTK_DIALOG_DESTROY_WITH_PARENT | GTK_DIALOG_MODAL);

   GtkWidget* dialog =
      gtk_dialog_new_with_buttons("Generating Key", NULL, flags, NULL);

   GtkWidget* label = gtk_label_new(" Generating new key, please wait...  \n");
   gtk_container_add(GTK_CONTAINER(GTK_DIALOG(dialog)->vbox), label);

   GtkWidget* progress_bar = gtk_progress_bar_new();
   gtk_progress_bar_set_pulse_step(GTK_PROGRESS_BAR(progress_bar),
                                   PROGRESS_PER_PULSE);
   gtk_container_add(GTK_CONTAINER(GTK_DIALOG(dialog)->vbox), progress_bar);

   guint timer_id = gtk_timeout_add(PULSE_INTERVAL, gtk_pulse_timeout,
                                    progress_bar);

   gtk_widget_show_all(dialog);

   while(gtk_events_pending())
      gtk_main_iteration();

   /* Register gtk_pulse so it will be called every so often when we embark
      on our prime generation quest...
   */
   /* this just updates the GUI; the GTK+ timeout function actually updates
      the progress bar. That's because the amount of time between pulses
      from the library is rather irregular, so the progress bar looks jerky.
   */
   Botan::global_state().set_ui(new GTK_Pulse);

   /* Not generally recommended, since it's slow and there's not much point.
      However, *because* it's slow, we'll want to put up a progress bar or
      something, and part of this whole thing is to show how to do that and get
      the pulse functions to do the right thing.
   */
   Botan::DL_Group group(1024, Botan::DL_Group::DSA_Kosherizer);
   key = new Botan::DSA_PrivateKey(group);

   gtk_timeout_remove(timer_id);
   Botan::global_state().set_ui(0); // unset the pulse function

   gtk_widget_destroy(dialog);

   do_save_key("Save New Key");

   /* new key, any old sigs are no longer useful */
   zap_sig();
   }

/*************************************************
* Load up a key                                  *
*************************************************/
static void get_key()
   {
   std::string fsname = get_filename("Select a DSA Key");

   if(fsname != "")
      {
      try {
         delete key;
         key = 0;
         zap_sig();

         /*
            A GTK_UI is a subclass of User_Interface that pops up a dialog that
            asks the user for a passphrase. It actually works quite well,
            though the fixed upper limit on the passphrase size is not
            ideal. Feel free to use it as-is or modify it however you like
            (gtk_ui.* is public domain).
         */
         GTK_UI ui;
         Botan::PKCS8_PrivateKey* p8_key = Botan::PKCS8::load_key(fsname, ui);
         key = dynamic_cast<Botan::DSA_PrivateKey*>(p8_key);
         if(!key)
            show_dialog("The key in " + fsname + " is not a DSA key",
                        "Failure");
      }
      catch(std::exception)
         {
         key = 0; // make sure it's not something random
         show_dialog("Loading the key from " + fsname + " failed.", "Failure");
         }
      }
   }

static void really_sign_buffer()
   {
   /* No key? Ask the user for one. */
   if(key == 0)
      get_key();
   sign_buffer();
   }

/*************************************************
* Clear the text buffer                          *
*************************************************/
static void new_buffer()
   {
   /*
      In theory, it would be nice to check if this was unsaved text and prompt
      to save it. However, this really isn't supposed to be a GTK+ example, so
      we won't.
   */
   gtk_text_buffer_set_text(buffer, "", -1);
   buffer_source = "";
   }

/*************************************************
* Put the contents of a file into the buffer     *
*************************************************/
static void open_buffer()
   {
   std::string filename = get_filename("Select File");

   if(filename == "")
      return;

   std::ifstream in(filename.c_str());

   new_buffer();
   buffer_source = filename;

   while(in.good())
      {
      char buf[1024] = { 0 };

      in.read(buf, 1024);
      size_t got = in.gcount();

      GtkTextIter iter;
      gtk_text_buffer_get_end_iter(buffer, &iter);
      gtk_text_buffer_insert(buffer, &iter, buf, got);
      }
   }

/*************************************************
* Save the signature to a file                   *
*************************************************/
static void save_sig()
   {
   std::string sig_file = buffer_source;

   /* No sig, nothing to save */
   const gchar* sig = gtk_entry_get_text(GTK_ENTRY(sig_view));
   if(strlen(sig) == 0)
      return;

   if(sig_file == "")
      sig_file = get_filename("Select Signature Output File");
   else
      sig_file += ".sig";

   std::ofstream out(sig_file.c_str());
   out << sig << std::endl;
   }

/*************************************************
* Save the current key                           *
*************************************************/
static void save_key()
   {
   do_save_key("Save Current Key");
   }

/*************************************************
* Common case of Save/Save As                    *
*************************************************/
static void do_save(const std::string& filename)
   {
   std::ofstream out(filename.c_str());

   GtkTextIter start, end;
   gtk_text_buffer_get_bounds(buffer, &start, &end);
   gchar* bits = gtk_text_buffer_get_text(buffer, &start, &end, FALSE);
   out.write(bits, strlen(bits));
   g_free(bits);
   buffer_source = filename;
   }

/*************************************************
* Save the buffer                                *
*************************************************/
static void save_buffer_as()
   {
   std::string filename = get_filename("Select Output File");
   if(filename != "")
      do_save(filename);
   }

/*************************************************
* Save the buffer                                *
*************************************************/
static void save_buffer()
   {
   if(buffer_source != "")
      do_save(buffer_source);
   else
      save_buffer_as();
   }

/*************************************************
* Make a menubar for the app                     *
*************************************************/
static GtkWidget* make_menubar(GtkWidget *window)
   {
   static GtkItemFactoryEntry menu_items[] = {
      { "/_File",          NULL,           NULL, 0, "<Branch>", NULL },
      { "/File/_New",      "<control>N",   new_buffer, 0, NULL, NULL },
      { "/File/_Open",     "<control>O",   open_buffer, 0, NULL, NULL },
      { "/File/_Save",     "<control>S",   save_buffer, 0, NULL, NULL },
      { "/File/Save _As",  NULL,           save_buffer_as, 0, NULL, NULL },
      { "/File/sep1",      NULL,           NULL, 0, "<Separator>", NULL },
      { "/File/Save Sig",  NULL,           save_sig, 0, NULL, NULL },
      { "/File/sep2",      NULL,           NULL, 0, "<Separator>", NULL },
      { "/File/_Quit",     "<control>Q",   gtk_main_quit, 0, NULL, NULL },

      { "/_Keys",          NULL,           NULL, 0, "<Branch>", NULL },
      { "/Keys/Open",      NULL,           get_key, 0, NULL, NULL },
      { "/Keys/_Generate", NULL,           gen_key, 0, NULL, NULL },
      { "/Keys/Save Current", NULL,        save_key, 0, NULL, NULL },

      { "/Signing",        NULL,           NULL, 0, "<Branch>", NULL },
      { "/Signing/Sign",   NULL,           really_sign_buffer, 0, NULL, NULL },

      { "/_Help",          NULL,           NULL, 0, "<LastBranch>", NULL },
      { "/Help/Help",      NULL,           show_help, 0, NULL, NULL },
      { "/Help/sep1",      NULL,           NULL, 0, "<Separator>", NULL },
      { "/Help/About",     NULL,           show_about, 0, NULL, NULL },
   };

   GtkAccelGroup* accel_group = gtk_accel_group_new();
   GtkItemFactory* item_factory =
      gtk_item_factory_new(GTK_TYPE_MENU_BAR, "<main>", accel_group);
   const gint nmenu_items = sizeof(menu_items) / sizeof(menu_items[0]);
   gtk_item_factory_create_items(item_factory, nmenu_items, menu_items, NULL);
   gtk_window_add_accel_group(GTK_WINDOW(window), accel_group);
   return gtk_item_factory_get_widget(item_factory, "<main>");
   }

int main(int argc, char *argv[])
   {
   gtk_init(&argc, &argv);

   try {
      Botan::LibraryInitializer init;

      /* Create a new top-level window */
      GtkWidget* window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
      gtk_window_set_title(GTK_WINDOW(window), "DSA Utility");
      gtk_signal_connect(GTK_OBJECT(window), "delete_event",
                         gtk_main_quit, NULL);

      /* Create the vbox to hold our stuff */
      GtkWidget* vbox = gtk_vbox_new(FALSE, 0);
      gtk_container_border_width(GTK_CONTAINER(vbox), 1);
      gtk_container_add(GTK_CONTAINER(window), vbox);

      /* Create the menu bar */
      GtkWidget *menubar = make_menubar(window);

      /* Create the entry that holds the signature */
      sig_view = gtk_entry_new();
      gtk_editable_set_editable(GTK_EDITABLE(sig_view), FALSE);

      /* Create the text box */
      GtkWidget* view = gtk_text_view_new();
      buffer = gtk_text_view_get_buffer(GTK_TEXT_VIEW(view));

      gtk_widget_set_size_request(view, 640, 480);
      gtk_text_buffer_set_text(buffer, "Some initial contents.", -1);

      // Resign it on each change: fast enough, but probably not really useful
      //g_signal_connect(G_OBJECT(buffer), "changed", sign_buffer, 0);
      g_signal_connect(G_OBJECT(buffer), "changed", zap_sig, 0);

      gtk_container_add(GTK_CONTAINER(vbox), menubar);
      gtk_container_add(GTK_CONTAINER(vbox), view);
      gtk_container_add(GTK_CONTAINER(vbox), sig_view);

      gtk_widget_show_all(window);

      gtk_main();
   }
   catch(std::exception& e)
      {
      std::cout << e.what() << std::endl;
      }
   return 0;
   }