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package Config::Autoload;

use strict;
use warnings;
use Carp qw/croak/;

our $VERSION = '0.01';

sub new {

    my $class = shift;
    my $file = shift;
    my $construct = shift;

    if ( ! -f $file ) {
        croak "The config file doesn't exist";
    } elsif ( ! -r $file ) {
        croak "The config file isn't readable";
    }

    if ( defined($construct) && ref($construct) ne 'CODE' ) {
        croak "The second argument for new() must be a coderef";
    }

    my $mtime = (stat($file))[9];
    my $c;

    if ( defined $construct ) {
        $c = $construct->($file);
        unless (ref($c) eq 'HASH') {
            croak "Not a hashref returned from the subroutine";
        }
    } else {
        $c = _construct($file);
    }

    bless { file => $file, mtime => $mtime, 
            c => $c, construct => $construct }, $class;
}
        
sub _construct {

    my $file = shift;
    my %hash;

    open HD,$file or croak $!;
    while(<HD>) {
        next if /^#|^$/;
        chomp;
        my ($k,$v) = split;
        $hash{$k} = $v;
    }
    close HD;

    return \%hash;
}

sub load_key {

    my $self = shift;
    my $key = shift;

    return undef unless defined $key;

    my $file = $self->{file}; 

    if ( ! -f $file ) {
        for (0..3) {
            select(undef,undef,undef,0.25);
            last if -f $file;
        }
    }

    croak "The config file seems not exists" unless -f $file;
    my $mtime = (stat($file))[9];

    if ( $mtime != $self->{mtime} ) {
        $self = __PACKAGE__->new($file,$self->{construct});
    }

    return $self->{c}->{$key};
}

1;


=head1 NAME

Config::Autoload - Autoloads the config file whenever it is changed

=head1 VERSION

Version 0.01


=head1 SYNOPSIS

    use Config::Autoload;

    my $config = Config::Autoload->new("/path/sample.conf");
    my $value = $config->load_key('key');

    # or

    my $config = Config::Autoload->new("/path/sample.conf",\&construct);
    my $value = $config->load_key('key');

    sub construct {

        my $file = shift;
        my %hash;

        open FD,$file or die $!;
        while(<FD>) {
            next if /^#|^$/;
            chomp;
            my ($k,$v) = split/ = /,$_;
            $hash{$k} =$v;
        }
        close FD;

        \%hash;
    }


=head1 METHODS

=head2 new()

Create an object. The full path to the config file is required.

    my $config = Config::Autoload->new("/path/sample.conf");

If the second argument is ignored, new() uses a defalut construct()
to built up a hash for storing the keys/values in the config file.