<?php
session_start();

/**
 * Finds file in a database and shows its content.
 *
 * @copyright Copyright (c) 2017 Paulina Laura Emilia <vilene@posteo.net>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

require_once 'includes/database.inc.php';

// Seconds in one non-leap year
define('ONE_YEAR', 31536000);

/**
 * Converts timestamp to HTTP-date format as defined by RFC 7231.
 *
 * @param int $timestamp
 *
 * @return string
 */
function httpDate($timestamp)
{
    return gmdate('D, d M Y H:i:s T', $timestamp);
}

try {
    // Get file from a database
    $q = $db->prepare('SELECT filename, mime, size, date FROM files
                       WHERE filename = (:filename)');
    $q->bindValue(':filename', $_GET['filename'], PDO::PARAM_STR);

    if ($q->execute()) {
        if ($q->rowCount() > 0) {
            $file = $q->fetch(PDO::FETCH_OBJ);

            // File metadata
            header('Content-Length: ' . $file->size);
            header('Content-Type: ' . $file->mime);

            // Cache control
            header('Cache-Control: public, immutable, max-age=' . ONE_YEAR);
            header('Expires: ' . httpDate(time() + ONE_YEAR));
            header('Last-Modified: ' . httpDate(strtotime($file->date)));
            header('Pragma: public');

            readfile(POMF_FILES_ROOT . $file->filename);
            exit;
        } else {
            throw new Exception('File not found', 404);
        }
    } else {
        $err = $q->errorInfo();
        throw new Exception('SQL error: ' . $err[2], 500);
    }
} catch (Exception $e) {
    header('Content-Type: text/plain', true, $e->getCode());

    echo $e->getCode() . ': ' . $e->getMessage();
    exit;
}