<?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("=== UPLOAD CHUNK START ===");
    error_log("POST data: " . print_r($_POST, true));
    error_log("FILES data: " . print_r($_FILES, true));
    error_log("Session data: " . print_r($_SESSION, true));

    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;
    }

    // Проверка CSRF токена
    $csrf_token = $_POST['csrf_token'] ?? '';
    error_log("CSRF token from POST: " . $csrf_token);
    error_log("CSRF token from session: " . ($_SESSION['csrf_token'] ?? 'NOT SET'));

    if (!verifyCSRFToken($csrf_token)) {
        error_log("ERROR: CSRF token verification failed");
        http_response_code(403);
        echo "CSRF token verification failed";
        exit;
    }

    // Проверка данных POST
    if (!isset($_POST['filename']) || !isset($_POST['index'])) {
        error_log("ERROR: Missing POST parameters");
        http_response_code(400);
        echo "Missing parameters";
        exit;
    }

    // Проверка загруженного файла
    if (!isset($_FILES['chunk']) || $_FILES['chunk']['error'] !== UPLOAD_ERR_OK) {
        error_log("ERROR: File upload error. Error code: " . ($_FILES['chunk']['error'] ?? 'NO_FILE'));
        http_response_code(400);
        echo "File upload error: " . ($_FILES['chunk']['error'] ?? 'NO_FILE');
        exit;
    }

    $filename = getSafeFileName($_POST['filename']);
    $index = intval($_POST['index']);

    error_log("Processing chunk: filename='$filename', index=$index");

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

    // Создание директории для чанков
    $tmpDir = CHUNK_DIR . $filename;
    error_log("Chunk directory: $tmpDir");

    if (!file_exists($tmpDir)) {
        if (!mkdir($tmpDir, 0755, true)) {
            error_log("ERROR: Cannot create chunk directory: $tmpDir");
            http_response_code(500);
            echo "Cannot create chunk directory";
            exit;
        }
        error_log("Created chunk directory: $tmpDir");
    }

    // Проверка прав на запись
    if (!is_writable($tmpDir)) {
        error_log("ERROR: Chunk directory is not writable: $tmpDir");
        http_response_code(500);
        echo "Chunk directory is not writable";
        exit;
    }

    $chunkPath = "$tmpDir/$index.part";
    error_log("Chunk path: $chunkPath");
    error_log("Temporary file: " . $_FILES['chunk']['tmp_name']);
    error_log("Chunk size: " . $_FILES['chunk']['size']);

    // Перемещение загруженного чанка
    if (move_uploaded_file($_FILES['chunk']['tmp_name'], $chunkPath)) {
        error_log("SUCCESS: Chunk saved to $chunkPath");
        http_response_code(200);
        echo "OK";
    } else {
        error_log("ERROR: Cannot move uploaded file to $chunkPath");
        error_log("PHP error: " . error_get_last()['message'] ?? 'Unknown error');
        http_response_code(500);
        echo "Cannot save chunk";
    }

    error_log("=== UPLOAD CHUNK END ===");
} catch (Exception $e) {
    error_log("EXCEPTION in upload_chunk.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 upload_chunk.php: " . $e->getMessage());
    error_log("Stack trace: " . $e->getTraceAsString());
    http_response_code(500);
    echo "Fatal error: " . $e->getMessage();
}