#!/usr/bin/env perl
use strict;
use warnings;
use DBI;
use Carp;
use English;

my $dbh = DBI->connect('dburl', 'dbuser', 'dbpassword', {AutoCommit => 0, RaiseError => 0}) or croak($EVAL_ERROR);

foreach my $fname (qw[pdi pitchover contactlight engineshutdown]) {
    print "Executing file $fname\n";
    open($my $ifh, '<', $fname) or croak($ERRNO);
    while((my $line = <$ifh>)) {
        chomp $line; # Remove linebreak character
  
        # Ignore empty lines and comments
        next if($line eq '' || $line =~ /^\#/);

        if(!$dbh->do($line)) {
            # It's a 1202 program alarm, abort the landing
            $dbh->rollback;
            croak($dbh->errstr);
        }
    }
    close $ifh;
}

# Tranquility base here, the Eagle has landed
$dbh->commit;

##</code><code>##

#!/usr/bin/env perl
use strict;
use warnings;
use DBI;
use Carp;
use English;

# Load the .pm files from the current directory. Not really recommended, but it's fine for testing and debugging
BEGIN {
    unshift @INC, '.';
};
use PDI;
use Pitchover;
use ContactLight;
use EngineShutdown;

my $dbh = DBI->connect('dburl', 'dbuser', 'dbpassword', {AutoCommit => 0, RaiseError => 0}) or croak($EVAL_ERROR);

my @modules;

push @modules, PDI->new(dbh => $dbh);
push @modules, Pitchover->new(dbh => $dbh);
push @modules, ContactLight->new(dbh => $dbh);
push @modules, EngineShutdown->new(dbh => $dbh);

foreach my $module (@modules) {
    if(!$module->executeProgram()) {
        $dbh->rollback;
        croak("Abort!");
    }
}

# Tranquility base here, the Eagle has landed
$dbh->commit;

##</code><code>##

package PDI;

use strict;
use warnings;
use English;

sub new {
    my ($proto, %config) = @_;
    my $class = ref($proto) || $proto;

    my $self = bless \%config, $class;

    return $self;
}

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

    # Slew to PDI attitude
    if(!$self->{dbh}->do("firststatement")) {
        return 0;
    }

    # Calculate burn time
    if(!$self->{dbh}->do("secondstatement")) {
        return 0;
    }

    # do some more complex stuff, like reading data from the database and using that to
    # decide if we need to open the helium valves
    my $selsth = $self->{dbh}->prepare_cached("SELECT valvename, valvestate FROM descentstage") or return 0;
    if(!$selsth->execute) {
        return 0;
    }
    while((my $line = $selsth->fetchrow_hashref)) {
        # complex logic here
    }
    $selsth->finish;

    return 1;
}

1;