<?php

// Включаем отображение всех ошибок для отладки
error_reporting(E_ALL);
ini_set('display_errors', 1);
ini_set('log_errors', 1);

session_start();

try {
    error_log("=== MERGE CHUNKS START ===");

    require_once __DIR__ . '/config.php';
    require_once __DIR__ . '/functions.php';

    // Проверка авторизации
    if (!isset($_SESSION['logged_in'])) {
        error_log("ERROR: User not logged in");
        http_response_code(403);
        echo "Not authorized";
        exit;
    }

    // Получение и проверка JSON данных
    $input = file_get_contents('php://input');
    error_log("Input data: " . $input);

    $data = json_decode($input, true);
    if (json_last_error() !== JSON_ERROR_NONE) {
        error_log("ERROR: JSON decode error: " . json_last_error_msg());
        http_response_code(400);
        echo "Invalid JSON data";
        exit;
    }

    error_log("Decoded data: " . print_r($data, true));

    // Проверка CSRF токена
    $csrf_token = $data['csrf_token'] ?? '';
    if (!verifyCSRFToken($csrf_token)) {
        error_log("ERROR: CSRF token verification failed");
        http_response_code(403);
        echo "CSRF token verification failed";
        exit;
    }

    $filename = getSafeFileName($data['filename'] ?? '');
    $total = intval($data['total'] ?? 0);

    error_log("Processing merge: filename='$filename', total=$total");

    // Валидация данных
    if (empty($filename) || $total <= 0) {
        error_log("ERROR: Invalid parameters");
        http_response_code(400);
        echo "Invalid parameters";
        exit;
    }

    // Валидация имени файла
    if (!validateFileName($filename)) {
        error_log("ERROR: Invalid filename: $filename");
        http_response_code(400);
        echo "Invalid filename";
        exit;
    }

    $tmpDir = CHUNK_DIR . $filename;
    $finalPath = UPLOAD_DIR . $filename;

    error_log("Chunk directory: $tmpDir");
    error_log("Final path: $finalPath");

    // Проверка существования директории с чанками
    if (!file_exists($tmpDir)) {
        error_log("ERROR: Chunk directory does not exist: $tmpDir");
        http_response_code(400);
        echo "Chunk directory not found";
        exit;
    }

    // Проверка всех чанков и подсчет общего размера
    $totalSize = 0;
    $missingChunks = [];

    for ($i = 0; $i < $total; $i++) {
        $partPath = "$tmpDir/$i.part";
        if (!file_exists($partPath)) {
            $missingChunks[] = $i;
        } else {
            $chunkSize = filesize($partPath);
            $totalSize += $chunkSize;
            error_log("Chunk $i size: $chunkSize bytes");
        }
    }

    if (!empty($missingChunks)) {
        error_log("ERROR: Missing chunks: " . implode(', ', $missingChunks));
        http_response_code(400);
        echo "Missing chunks: " . implode(', ', $missingChunks);
        exit;
    }

    error_log("Total file size: $totalSize bytes");
    error_log("Max allowed size: " . getMaxFileSize() . " bytes");

    // Проверка размера файла
    if ($totalSize > getMaxFileSize()) {
        error_log("ERROR: File too large");
        // Очистка чанков
        for ($i = 0; $i < $total; $i++) {
            @unlink("$tmpDir/$i.part");
        }
        @rmdir($tmpDir);
        http_response_code(413); // Payload Too Large
        echo "File too large";
        exit;
    }

    // Проверка прав на запись в директорию загрузок
    if (!is_writable(UPLOAD_DIR)) {
        error_log("ERROR: Upload directory is not writable: " . UPLOAD_DIR);
        http_response_code(500);
        echo "Upload directory is not writable";
        exit;
    }

    // Объединение чанков
    error_log("Starting file merge");
    $out = fopen($finalPath, 'wb');
    if (!$out) {
        error_log("ERROR: Cannot create final file: $finalPath");
        http_response_code(500);
        echo "Cannot create final file";
        exit;
    }

    for ($i = 0; $i < $total; $i++) {
        $partPath = "$tmpDir/$i.part";
        error_log("Merging chunk $i from $partPath");

        $in = fopen($partPath, 'rb');
        if (!$in) {
            error_log("ERROR: Cannot open chunk $i");
            fclose($out);
            @unlink($finalPath);
            http_response_code(500);
            echo "Cannot open chunk $i";
            exit;
        }

        $copied = stream_copy_to_stream($in, $out);
        fclose($in);

        error_log("Copied $copied bytes from chunk $i");

        // Удаление чанка после успешного копирования
        if (!unlink($partPath)) {
            error_log("WARNING: Cannot delete chunk $i");
        }
    }

    fclose($out);

    // Удаление директории чанков
    if (!rmdir($tmpDir)) {
        error_log("WARNING: Cannot delete chunk directory: $tmpDir");
    }

    $finalSize = filesize($finalPath);
    error_log("Final file size: $finalSize bytes");
    error_log("SUCCESS: File merged successfully");

    http_response_code(200);
    echo "OK";

    error_log("=== MERGE CHUNKS END ===");
} catch (Exception $e) {
    error_log("EXCEPTION in merge_chunks.php: " . $e->getMessage());
    error_log("Stack trace: " . $e->getTraceAsString());
    http_response_code(500);
    echo "Server error: " . $e->getMessage();
} catch (Error $e) {
    error_log("FATAL ERROR in merge_chunks.php: " . $e->getMessage());
    error_log("Stack trace: " . $e->getTraceAsString());
    http_response_code(500);
    echo "Fatal error: " . $e->getMessage();
}