ch10.067_best

Perl Best Practices the source code

##############################################################################
##   Code fragment (Recommended) from Chapter 10 of "Perl Best Practices"   ##
##     Copyright (c) O'Reilly & Associates, 2005. All Rights Reserved.      ##
##  See: http://www.oreilly.com/pub/a/oreilly/ask_tim/2001/codepolicy.html  ##
##############################################################################


# Standard modules...
use strict;
use warnings;
use IO::Prompt;
use Carp;
use English qw( -no_match_vars );
use Data::Alias;
use Readonly;


Readonly my @CONFIG_PATHS
    => qw( dev/config dev/config/alt ~/config /usr/config );

Readonly my $REMOTE_SERVER => '[e-mail]';
Readonly my $MAX_TRIES     => 100;

Readonly my $QUIT => qr/\A q(?:uit)? \z/ixms;

sub init_from  {
    return sleep 2;
}

sub connect_to {
    my ($server, $opt_ref) = @_;
    sleep $opt_ref->{timeout};
    return rand 0 > 0.7 ? 'pipe' : undef;
}

sub fibonacci {
    my ($n) = @_;
    return 1 if $n < 2;
    return fibonacci($n-1) + fibonacci($n-2);
}

my $prompt_str = '> ';

# Initialize from any config files...
print {*STDERR} 'Initializing...';

for my $possible_config ( @CONFIG_PATHS ) {
    print {*STDERR} '.';
    init_from($possible_config);
}
print {*STDERR} "done\n";
 
# Connect to remote server...
print {*STDERR} 'Connecting to server...';

my $connection;
TRY:
for my $try (1..$MAX_TRIES) {
    print {*STDERR} '.';
    $connection = connect_to($REMOTE_SERVER, { timeout => fibonacci($try) });
    last TRY if $connection;
}
croak "Can't contact server ($REMOTE_SERVER)"
    if not $connection;
print {*STDERR} "done\n";
 
# Interactive portion of the program starts here...

while (my $cmd = prompt($prompt_str, -fail_if=>$QUIT)) {
    remote_execute($connection, $cmd) 
        or carp "Unknown command: $cmd";
}



sub remote_execute {
    my ($connection, $cmd) = @_;
    print "remotely executing via $connection: $cmd\n";
    return 1;
}