<?php
require_once '../config.php';

// 🔥 Enable logging (NOT display in production)
ini_set('log_errors', 1);
ini_set('error_log', __DIR__ . '/download_error.log');

$filePath = realpath("../docs") . DIRECTORY_SEPARATOR;
$zipPath  = realpath("../") . "/zip_docs/";

// Ensure zip directory exists
if (!is_dir($zipPath)) {
    mkdir($zipPath, 0775, true);
}

/**
 * ============================
 * VALIDATE INPUT
 * ============================
 */
$list = $_POST['list'] ?? '';

if (is_array($list)) {
    $list = implode(',', $list); // convert array → string
}

$docNos = array_filter(array_map('intval', explode(',', $list)));

if (empty($docNos)) {
    die('Invalid data');
}

/**
 * ============================
 * SINGLE FILE DOWNLOAD
 * ============================
 */
if (count($docNos) === 1) {

    $file = $docNos[0];

    $file1 = $filePath . "$file/$file.xls";
    $file2 = $filePath . "$file/$file.xlsx";

    if (file_exists($file1)) {
        $downloadFile = $file1;
    } elseif (file_exists($file2)) {
        $downloadFile = $file2;
    } else {
        die('File not found');
    }

    // Clean output buffer
    if (ob_get_length()) ob_end_clean();

    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="' . basename($downloadFile) . '"');
    header('Content-Length: ' . filesize($downloadFile));
    header('Cache-Control: no-cache, must-revalidate');

    readfile($downloadFile);
    exit;
}

/**
 * ============================
 * MULTIPLE FILES → ZIP
 * ============================
 */
$zipName = 'assignments_' . time() . '.zip';
$zipFile = $zipPath . $zipName;

$zip = new ZipArchive();

if ($zip->open($zipFile, ZipArchive::CREATE | ZipArchive::OVERWRITE) !== TRUE) {
    die('Could not create ZIP');
}

foreach ($docNos as $file) {

    $file1 = $filePath . "$file/$file.xls";
    $file2 = $filePath . "$file/$file.xlsx";

    if (file_exists($file1)) {
        $zip->addFile($file1, "$file.xls");
    } elseif (file_exists($file2)) {
        $zip->addFile($file2, "$file.xlsx");
    }
}

$zip->close();

if (!file_exists($zipFile)) {
    die('ZIP creation failed');
}

// Clean output buffer
if (ob_get_length()) ob_end_clean();

header('Content-Type: application/zip');
header('Content-Disposition: attachment; filename="' . basename($zipFile) . '"');
header('Content-Length: ' . filesize($zipFile));
header('Cache-Control: no-cache, must-revalidate');

readfile($zipFile);

// Cleanup (important)
unlink($zipFile);

exit;