#!/usr/bin/perl

#  main.fcgi is part of Calliope, an open source music management system.
#  main.fcgi is the same as home.fcgi, they function as protected and
#  unprotected gateways to calliope, respectively.
#
#  This is the interface between the apache fast cgi module, and the
#  Dispatch module of calliope, which accepts all incoming web requests.
#  It's based on several snippets of example code I found on the web, 
#  which i can no longer find.
#
#  Changes Copyright (C) 02006-02007 Neil Verplank
#  http://neil.verplank.org/opensource/calliope/
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 1, or (at your option)
#  version 2.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  See ~/LICENSE for more details.


use lib "/usr/local/calliope/lib";
use strict;
use Web::Dispatch ();
use CGI::Fast;

my $handling_request = 0;
my $exit_requested = 0;

my $request;


# sig_handler is "called by" fastcgi when it decides to terminate
# a no longer needed thread.  exiting directly causes an error, 
# because this thread is also in an infinite while loop,
# and must receive one more request in order to terminate
# gracefully.  so, we set the global exit flag, and return a
# thumbs up.
sub sig_handler {
    $exit_requested = 1;
    return 1;
}

$SIG{USR1} = \&sig_handler;
$SIG{TERM} = \&sig_handler;
$SIG{PIPE} = sub {die 'SIGPIPE\n';};

# the main entry point - receives incoming requests, attempts to handle
# them and their potential failure gracefully, and aborts upon a fatal
# error or SIGPIPE.
while ($request = new CGI::Fast) {
    eval {&abort_request;} if (!eval {&do_request;} && $@ ne 'SIGPIPE\n');
    $handling_request = 0;
    last if $exit_requested;
}

exit(0);

# sends a received request to calliope's web entry point, Dispatch.
sub do_request() {
    $handling_request = 1;
    my $result = &Web::Dispatch::dispatch($request); # 1 if no DB connection
    return 1;
}

# what to do when it all goes pear-shaped.
sub abort_request() {
    $exit_requested = 1; # assume the error isn't recoverable
    print STDERR "fatal error in process $$ (fastcgi), request aborted, shutting down: $@\n";
}