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lib/Weather/GHCN/CacheURI.pm  view on Meta::CPAN

            $self->store($key, $content) if $content;
            return ($FROM_URI, $content);
        } else {
            # page is unchanged, so use the cached file
            my $content = $self->load($key);
            return ($FROM_CACHE, $content);
        }
    }

    # there's no cached file, so get the page from the URI and cache it
    my $content = get($uri);
    $self->store($key, $content) if $content;
    return ($FROM_URI, $content);
}

method _fetch_refresh_n_days ($uri, $cutoff_mtime) {
    # check whether the cache or page is older than N days
    # if the cache file is younger than N days ago, use it
    # otherwise get the latest page from the server
    # check the server if the file is older than this year

    my $key = $self->_uri_to_key($uri);
    my $file = $self->_path_to_key($key);

    my $st = stat $file;

    if ($st and $st->mtime >= $cutoff_mtime) {
        # the cached file we have is at or new than the cutoff, so we'll use it
        my $content = $self->load($key);
        return ($FROM_CACHE, $content);
    }

    # get the mtime for the URI
    my ($ctype, $doclen, $mtime, $exp, $svr) = head($uri)
        or croak '*E* unable to fetch header for: ' . $uri;

    # our cached file is older than the cutoff, but if it's up to date
    # with the web page then we can use it
    if ($st and $st->mtime >= $mtime) {
        # web page hasn't changed since it was cached. so we'll use it
        my $content = $self->load($key);
        return ($FROM_CACHE, $content);
    }

    # there's no cached file, or the cached file is out of date, so
    # we get the page from the URI and cache it
    my $content = get($uri);
    $self->store($key, $content) if $content;
    return ($FROM_URI, $content);
}

method _fetch_without_cache ($uri) {
    # check for a fresher copy on the server
    my $key = $self->_uri_to_key($uri);

    my $content = get($uri);
    return ($FROM_URI, $content);
}

method _uri_to_key ($uri) {
    my @parts = split m{ $FSLASH }xms, $uri;
    my $key = $parts[-1];  # use the last part as the key

    # this transformation is for testing using CPAN pages and is not
    # necessary for the NOAA GHCN pages we actually deal with
    $key =~ s{ [:] }{}xmsg;

    return $key;
}

method _path_to_key ($uri) {
    return if not defined $uri;

    my $key = $self->_uri_to_key( $uri );

    my $filepath = path($_cachedir)->child($key)->stringify;

    return $filepath;
}

######################################################################
# Private subroutines
######################################################################

sub _read_file ( $file ) {
    return path($file)->slurp_utf8;
}

sub _write_file ( $file, $data ) {
    return path($file)->spew_utf8( $data );
}


1;

__END__

=head1 AUTHOR

Gary Puckering (jgpuckering@rogers.com)

=head1 LICENSE AND COPYRIGHT

Copyright 2022, Gary Puckering

=cut