<?php
// api/upload_file.php - Upload file to Google Drive via Apps Script Web App
header('Content-Type: application/json; charset=utf-8');
header('Access-Control-Allow-Origin: *');

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

// Set higher limits for large file uploads to GAS (70MB+ requires a lot of memory for base64 & JSON)
set_time_limit(600);
ini_set('memory_limit', '1024M');
ini_set('post_max_size', '128M');
ini_set('upload_max_filesize', '128M');

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    echo json_encode(['status' => 'error', 'message' => 'Invalid request method']);
    exit;
}

if (!isset($_FILES['file']) || $_FILES['file']['error'] !== UPLOAD_ERR_OK) {
    echo json_encode(['status' => 'error', 'message' => 'No file uploaded or upload error']);
    exit;
}

$folderId = $_POST['folderId'] ?? '';
if (empty($folderId)) {
    echo json_encode(['status' => 'error', 'message' => 'Missing Google Drive Folder ID. ผู้ดูแลระบบยังไม่ได้ตั้งค่า Folder ID ให้กับหน่วยงานนี้']);
    exit;
}

try {
    $dbInfo = getDbConnection();
    $pdo = $dbInfo['pdo'];

    // Get GAS URL from system settings
    $settingsStmt = $pdo->query("SELECT setting_value FROM system_settings WHERE setting_key = 'gdrive_gas_url'");
    $gasUrlRow = $settingsStmt->fetch();
    $gasUrl = $gasUrlRow ? $gasUrlRow['setting_value'] : '';

    if (empty($gasUrl)) {
        echo json_encode(['status' => 'error', 'message' => 'Super Admin ยังไม่ได้ตั้งค่า Google Apps Script Web App URL']);
        exit;
    }

    $fileTmpPath = $_FILES['file']['tmp_name'];
    $fileName = $_FILES['file']['name'];
    $fileMimeType = mime_content_type($fileTmpPath);
    if (!$fileMimeType) {
        $fileMimeType = $_FILES['file']['type'];
    }

    $fileData = file_get_contents($fileTmpPath);
    $base64 = base64_encode($fileData);

    $payload = json_encode([
        'filename' => $fileName,
        'mimeType' => $fileMimeType,
        'base64' => $base64,
        'folderId' => $folderId
    ]);

    // Send to GAS via cURL
    $ch = curl_init($gasUrl);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, false); // Handle redirect manually to prevent POST/GET confusion
    curl_setopt($ch, CURLOPT_HEADER, true); // Include headers to parse Location
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
    curl_setopt($ch, CURLOPT_TIMEOUT, 120);
    curl_setopt($ch, CURLOPT_HTTPHEADER, [
        'Content-Type: application/json'
    ]);

    $response = curl_exec($ch);
    if(curl_errno($ch)) {
        throw new \Exception(curl_error($ch));
    }
    
    $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
    $headerSize = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
    $headerStr = substr($response, 0, $headerSize);
    $bodyStr = substr($response, $headerSize);
    curl_close($ch);

    // If GAS rejects because payload is too large
    if ($httpCode === 413) {
        echo json_encode(['status' => 'error', 'message' => 'ขนาดไฟล์ใหญ่เกินกว่าที่ Google Drive จะรับได้ (จำกัดการส่งข้อมูลที่ 50MB)']);
        exit;
    }

    // If GAS returns a redirect (e.g. 302, 307)
    if ($httpCode >= 300 && $httpCode < 400) {
        if (preg_match('/^Location:\s*([^\r\n]+)/im', $headerStr, $matches)) {
            $redirectUrl = trim($matches[1]);
            
            // Force a GET request to the redirect URL
            $ch2 = curl_init($redirectUrl);
            curl_setopt($ch2, CURLOPT_RETURNTRANSFER, true);
            curl_setopt($ch2, CURLOPT_FOLLOWLOCATION, true); 
            curl_setopt($ch2, CURLOPT_HTTPGET, true); // Force GET
            curl_setopt($ch2, CURLOPT_TIMEOUT, 60);
            
            $bodyStr = curl_exec($ch2);
            if(curl_errno($ch2)) {
                throw new \Exception(curl_error($ch2));
            }
            curl_close($ch2);
        } else {
            throw new \Exception("GAS returned redirect but no Location header found.");
        }
    }

    $resData = json_decode($bodyStr, true);
    if ($resData && isset($resData['status']) && $resData['status'] === 'success') {
        echo json_encode([
            'status' => 'success',
            'message' => 'File uploaded to Google Drive',
            'fileId' => $resData['fileId'] ?? null,
            'url' => $resData['url'] ?? null,
            'fileName' => $fileName,
            'fileSize' => $_FILES['file']['size']
        ]);
    } else {
        echo json_encode(['status' => 'error', 'message' => 'Google Apps Script Error: ' . ($resData['message'] ?? $response)]);
    }

} catch (\Exception $e) {
    echo json_encode(['status' => 'error', 'message' => 'Upload Error: ' . $e->getMessage()]);
}
?>