package pidfile;

use 5.006;
use strict;
use warnings;

our $VERSION = '0.0.1';

use Carp;
use IO::File;
use Fcntl qw(:flock);
use File::Basename;
use File::Spec;

our %PF_Default = (
    path => '/tmp',
    name => basename($0),
    mode => 0644,
);

# Preloaded methods go here.

sub new {
    my ( $class, %args ) = @_;
    my %pf = ( %PF_Default, %args );
    croak "path => $pf{path} is not a directory" unless -d $pf{path};
    croak "path => $pf{path} is not readable"    unless -r _;
    croak "path => $pf{path} is not writeable"   unless -w _;
    croak "name must be set" unless defined $pf{name} and length $pf{name};

    return bless \%pf, $class;
}

sub pidfile {
    my $s = shift;
    return $s->{file} ||= File::Spec->catfile($s->{path}, $s->{name}.".pid");
}

sub activate {
    my $s = shift;
    croak sprintf "%s contains a living pid %d\n", $s->pidfile, $s->getpid
      if ( $s->is_alive );
    $s->setpid;
}

sub setpid {
    my $s = shift;
    my $f = IO::File->new( $s->pidfile, O_RDWR | O_CREAT, $PF_Default{mode} );
    croak sprintf "can't open %s for writing: $!\n", $s->pidfile
      unless defined $f;
    croak sprintf "can't lock_ex %s: $!\n", $s->pidfile
      unless flock $f, LOCK_EX;
    $f->setpos(0);
    $f->truncate(0);
    $f->print( "$$", $/ );
    $f->close;
    return 1;
}

sub getpid {
    my $s = shift;
    my $f = IO::File->new( $s->pidfile, O_RDONLY );
    croak sprintf "can't open %s for reading: $!\n", $s->pidfile
      unless defined $f;
    croak sprintf "can't lock_sh %s: $!\n", $s->pidfile
      unless flock $f, LOCK_SH;
    my $l = $f->getline; 
    $f->close; 
    chomp $l;
    croak sprintf "%s contained non-numeric pid\n", $s->pidfile
      unless $l == $l + 0;
    return $l+0;
}

sub is_alive {
    my $s = shift;
    return 0 unless -f $s->pidfile;
    return kill 0, $s->getpid;
}   

sub is_self {
    my $s = shift;
    return 0 unless -f $s->pidfile;
    return $$ == $s->getpid;
}
    
sub DESTROY {
    my $s = shift;
    unlink $s->pidfile if $s->is_self;
}   
    
1;  
__END__