<?php

class PHP_DW {
    private $dw_dir = 'downloads';
    private $cnt_dir = '.count';

    function __construct($dw_dir = false, $cnt_dir = false) {

        if ($dw_dir) {
            $this->dw_dir = $dw_dir;
        }

        if ($cnt_dir) {
            $this->cnt_dir = $cnt_dir;
        }
    }

    private function __get_full_path($path) {
        if (basename($path) !== $path) {
            return null;
        }

        return $this->dw_dir . '/' . $path;
    }

    private function __incr_count($filename) {
        $fh = @fopen($this->cnt_dir . '/' . $filename . '.cnt', "a+");

        if (is_resource($fh) and flock($fh, LOCK_EX)) {
            rewind($fh);

            $count = fgets($fh);

            if ($count === false)
                $count = 0;

            $count++;

            ftruncate($fh, 0);
            fwrite($fh, $count);

            flock($fh, LOCK_UN);

            fclose($fh);
        }
    }

    public function download($filename) {
        /* according to stat(2) */
        define('S_IFMT', 0170000);
        define('S_IFREG', 0100000);

        $path = $this->__get_full_path($filename) or die('invalid file');

        $fh = @fopen($path, 'rb');

        if ($fh) {
            $fstats = fstat($fh);

            /* check if the target is a regular file */
            if (S_IFREG == ($fstats['mode'] & S_IFMT)) {
                $this->__incr_count($filename);

                header('Content-Description: File Transfer');
                header('Content-Disposition: attachment; filename=' . $filename);
                header('Content-Length: '. $fstats['size']);
                header('Cache-Control: private');

                echo(fread($fh, $fstats['size']));
            } else {
                echo($path . ': is not a regular file');
            }

            fclose($fh);
        } else {
            echo($path . ': no such file or directory');
        }
    }

    public function get_count($filename) {
        if (!$this->__get_full_path($filename))
            return 0;

        $fh = @fopen($this->cnt_dir . '/' . $filename . '.cnt', "r");

        if (!is_resource($fh))
            return 0;

        $count = fgets($fh) or '0';

        fclose($fh);

        return $count;
    }

    public function get_count_dir() {
        return $this->cnt_dir;
    }

    public function get_download_dir() {
        return $this->dw_dir;
    }
}
?>