<?php
/**
 * Download Attachment API
 *
 * Serves file downloads for ticket attachments
 */

session_start();
require_once dirname(__DIR__) . '/config/config.php';
require_once dirname(__DIR__) . '/models/AttachmentModel.php';
require_once dirname(__DIR__) . '/models/TicketModel.php';

// Check authentication
if (!isset($_SESSION['user']) || !isset($_SESSION['user']['user_id'])) {
    http_response_code(401);
    header('Content-Type: application/json');
    echo json_encode(['success' => false, 'error' => 'Authentication required']);
    exit;
}

// Get attachment ID
$attachmentId = $_GET['id'] ?? null;
if (!$attachmentId || !is_numeric($attachmentId)) {
    http_response_code(400);
    header('Content-Type: application/json');
    echo json_encode(['success' => false, 'error' => 'Valid attachment ID is required']);
    exit;
}

$attachmentId = (int)$attachmentId;

try {
    $attachmentModel = new AttachmentModel();

    // Get attachment details
    $attachment = $attachmentModel->getAttachment($attachmentId);
    if (!$attachment) {
        http_response_code(404);
        header('Content-Type: application/json');
        echo json_encode(['success' => false, 'error' => 'Attachment not found']);
        exit;
    }

    // Verify the associated ticket exists and user has access
    $conn = new mysqli(
        $GLOBALS['config']['DB_HOST'],
        $GLOBALS['config']['DB_USER'],
        $GLOBALS['config']['DB_PASS'],
        $GLOBALS['config']['DB_NAME']
    );
    if ($conn->connect_error) {
        http_response_code(500);
        header('Content-Type: application/json');
        echo json_encode(['success' => false, 'error' => 'Database connection failed']);
        exit;
    }

    $ticketModel = new TicketModel($conn);
    $ticket = $ticketModel->getTicketById($attachment['ticket_id']);

    if (!$ticket) {
        $conn->close();
        http_response_code(404);
        header('Content-Type: application/json');
        echo json_encode(['success' => false, 'error' => 'Associated ticket not found']);
        exit;
    }

    // Check if user has access to this ticket based on visibility settings
    if (!$ticketModel->canUserAccessTicket($ticket, $_SESSION['user'])) {
        $conn->close();
        http_response_code(403);
        header('Content-Type: application/json');
        echo json_encode(['success' => false, 'error' => 'Access denied to this ticket']);
        exit;
    }

    $conn->close();

    // Build file path
    $uploadDir = $GLOBALS['config']['UPLOAD_DIR'] ?? dirname(__DIR__) . '/uploads';
    $filePath = $uploadDir . '/' . $attachment['ticket_id'] . '/' . $attachment['filename'];

    // Security: Verify the resolved path is within the uploads directory (prevent path traversal)
    $realUploadDir = realpath($uploadDir);
    $realFilePath = realpath($filePath);

    if ($realFilePath === false || $realUploadDir === false || strpos($realFilePath, $realUploadDir) !== 0) {
        http_response_code(403);
        header('Content-Type: application/json');
        echo json_encode(['success' => false, 'error' => 'Access denied']);
        exit;
    }

    // Check if file exists
    if (!file_exists($realFilePath)) {
        http_response_code(404);
        header('Content-Type: application/json');
        echo json_encode(['success' => false, 'error' => 'File not found on server']);
        exit;
    }

    // Use the validated real path
    $filePath = $realFilePath;

    // Determine if we should display inline or force download
    $inline = isset($_GET['inline']) && $_GET['inline'] === '1';
    $inlineTypes = ['image/jpeg', 'image/png', 'image/gif', 'image/webp', 'application/pdf', 'text/plain'];

    // Set headers
    $disposition = ($inline && in_array($attachment['mime_type'], $inlineTypes)) ? 'inline' : 'attachment';

    // Sanitize filename for Content-Disposition
    $safeFilename = preg_replace('/[^\w\s\-\.]/', '_', $attachment['original_filename']);

    header('Content-Type: ' . $attachment['mime_type']);
    header('Content-Disposition: ' . $disposition . '; filename="' . $safeFilename . '"');
    header('Content-Length: ' . $attachment['file_size']);
    header('Cache-Control: private, max-age=3600');
    header('X-Content-Type-Options: nosniff');

    // Prevent PHP from timing out on large files
    set_time_limit(0);

    // Clear output buffer
    if (ob_get_level()) {
        ob_end_clean();
    }

    // Stream file
    $handle = fopen($filePath, 'rb');
    if ($handle === false) {
        http_response_code(500);
        header('Content-Type: application/json');
        echo json_encode(['success' => false, 'error' => 'Failed to open file']);
        exit;
    }

    while (!feof($handle)) {
        echo fread($handle, 8192);
        flush();
    }

    fclose($handle);
    exit;

} catch (Exception $e) {
    http_response_code(500);
    header('Content-Type: application/json');
    echo json_encode(['success' => false, 'error' => 'Failed to download attachment']);
    exit;
}