#!perl
#
###########################################################
# This script is an attempt at creating a cgiapp run mode
# that dynamically generates HTML lines, and displays them
# as soon as they are available. This in contrast
# to the standard cgiapp mode where the HTML content is 
# returned in bulk by the run mode, and cgiapp prints it
# all in one go, at the very end of the transaction.
#
# This particular attempt uses the CGI::Application::Plugin::Streaming
# plugin to stream the dynamically created content to STDOUT.
#
# It's implemented by the stream_dynamic_html() method, which 
# does the following:
#
# - Opens a temporary HTML file
# - invokes the stream_file() method on it
# - Prints the dynamically generated HTML content to the temp file
# - Closes the file.
#
# As it turns out, this does not work for two reasons
#
# a) Invoking stream_file() on a file that is still open
#    and being written to does not work. Instad of
#    receiving an HTML file with the content, the browser
#    receives the streammed content as a text file 
#    which only contains the single digit 1. If I try to
#    write the complete HTML content to the temp file, 
#    then close it and start the file_stream(),
#    then I get the full HTML content, but this content 
#    is not being displayed as you go. It only becomes 
#    available in bulk at the end of the transaction.
#
# b) stream_file() does not actually display the HTML
#    file's content as a page. Instead, it sends it to the 
#    browser as a "file" to be saved to disk or opened with 
#    an appropriate application
#
# To try the code:
# - Create a script cgiapp_streaming_with_authentication.cgi which
#   runs the CgiappStreamingWithAuthentication app.
# - Set $fpath_to_stream and $temp_dynamic_html_fpath 
#   to pathes on your system, which can be written to by 
#   your web server.
# - Clear cookies
# - Load cgiapp_streaming_with_authentication in your 
#   browser
# - Login as u=guest, p=1234
# - Click on the 'Stream static file' link
#   => This will download a text file and ask you to save it
#      to disk, or open it.
# - Click on 'Stream dynamic HTML page' link.
#   => - This will download a file called 
#        streamed_dynamic_content.html
#        (whose content is generated dynamically), and ask 
#        you to save it to disk, or open it.
#      - Notice how it takes a few seconds before it 
#        prompts you to open or save the file (because 
#        the script that generates the HTML content sleeps
#        for one second after each line it prints to the 
#        temp file).
#
#      - Notice how the file does not contain the HTML code 
#        generated by stream_dynamic_html(). It only 
#        contains the single digit 1.
###########################################################

use strict;
use warnings;


package CgiappStreamingWithAuthentication;
use base 'CGI::Application';


my $script_name = 'cgiapp_streaming_with_authentication.cgi';
my $fpath_to_stream = '/hello.txt';
my $file_type = 'text/plain';
my $temp_dynamic_html_fpath = '/streamed_dynamic_content.html';

use CGI::Application::Plugin::Stream (qw/stream_file/);

my $use_authentication = 1;

if ($use_authentication) {
	use CGI::Application::Plugin::Authentication;
	CgiappStreamingWithAuthentication->authen->config(
     		 DRIVER => [ 'Generic', { guest => '1234'} ],
      	 POST_LOGIN_RUNMODE => 'welcome',
   	  	 LOGOUT_RUNMODE => "logout"
	);
	CgiappStreamingWithAuthentication->authen->protected_runmodes(':all');	
}

sub setup {
     my $self = shift;
     $self->start_mode('welcome');
     $self->run_modes(
             'welcome' => "welcome",
             'stream_static_file' => "stream_static_file",
             'stream_dynamic_html' => "stream_dynamic_html",
     );
     $self->mode_param('dlg');
}

sub stream_dynamic_html {
	my ($self) = @_;

	$| = 1;
	
	open TEMP_HTML_FILE, ">$temp_dynamic_html_fpath";
	my $q = $self->query();
	
	print TEMP_HTML_FILE $q->start_html(-title => 'HTML page dynamically streamed to scean');
	print TEMP_HTML_FILE $q->h3('HTML page dynamically streamed to scean');
	
	print TEMP_HTML_FILE $q->p("The following lines will be printed at 1 sec interval.");
	for (my $ii=0; $ii<3; $ii++) {
		print TEMP_HTML_FILE $q->p("This is line $ii.\n");
		sleep(1);
	}

	print TEMP_HTML_FILE $q->p()."\n";
	print TEMP_HTML_FILE "<a href=\"$script_name?dlg=stream_dynamic_html\">Stream dynamic HTML page</a><br/>\n";
	print TEMP_HTML_FILE "<a href=\"$script_name?dlg=stream_static_file\">Stream static file</a><br/>\n";

	print TEMP_HTML_FILE $q->end_html();

	close TEMP_HTML_FILE;
	
	$self->stream_file($temp_dynamic_html_fpath, 10);
	


}

sub stream_static_file {
	my ($self) = @_;
	
	$| = 1;
	$self->stream_file( $fpath_to_stream, 10);
	
}

sub welcome {
     my $self = shift;

     # Get CGI query object
     my $q = $self->query();

     my $output = '';
     $output .= $q->start_html(-title => 'Welcome to CgiappStreamingWithAuthentication!');
     
     my $user_name = $self->authen->username;
     $output .= $q->h3("Hello, '$user_name'");

	 $output .=  $q->p()."\n";
	 $output .=  "<a href=\"$script_name?dlg=stream_dynamic_html\">Stream dynamic HTML page</a><br/>\n";
	 $output .=  "<a href=\"$script_name?dlg=stream_static_file\">Stream static file</a><br/>\n";
	 	     
     $output .= $q->end_html();

     return $output;
}


1;