<?php
require_once '../include/init.php';
require_once '../include/auth.php';

// --- Security Check: Only Admin can access this page ---
if (!isAdmin()) {
    header('Content-Type: application/json');
    http_response_code(403); // Forbidden
    echo json_encode(['success' => false, 'message' => 'You do not have permission to perform this action.']);
    exit;
}

header('Content-Type: application/json');

$response = [
    'success' => false,
    'message' => 'An unknown error occurred.',
    'path' => null
];

$uploadDir = '../data/images/backgrounds/';

// Create directory if it doesn't exist
if (!is_dir($uploadDir)) {
    if (!mkdir($uploadDir, 0755, true)) {
        http_response_code(500);
        $response['message'] = 'Failed to create upload directory.';
        echo json_encode($response);
        exit;
    }
}

if (isset($_FILES['background']) && $_FILES['background']['error'] === UPLOAD_ERR_OK) {
    $file = $_FILES['background'];
    $tabId = isset($_POST['tab_id']) ? intval($_POST['tab_id']) : 0;

    // --- Validation ---
    // Size check (e.g., 5MB limit)
    if ($file['size'] > 5 * 1024 * 1024) {
        http_response_code(400);
        $response['message'] = 'File is too large. Maximum size is 5MB.';
        echo json_encode($response);
        exit;
    }

    // Type check
    $allowedTypes = ['image/jpeg', 'image/png', 'image/gif', 'image/webp'];
    $fileInfo = finfo_open(FILEINFO_MIME_TYPE);
    $mimeType = finfo_file($fileInfo, $file['tmp_name']);
    finfo_close($fileInfo);

    if (!in_array($mimeType, $allowedTypes)) {
        http_response_code(400);
        $response['message'] = 'Invalid file type. Only JPG, PNG, GIF, and WEBP are allowed.';
        echo json_encode($response);
        exit;
    }

    // --- File Processing ---
    // Find and delete any existing background for this tab
    $existing_files = glob($uploadDir . 'tab_' . $tabId . '.*');
    foreach ($existing_files as $file_to_delete) {
        unlink($file_to_delete);
    }
    
    $extension = pathinfo($file['name'], PATHINFO_EXTENSION);
    $fileName = 'tab_' . $tabId . '.' . $extension;
    $destination = $uploadDir . $fileName;

    if (move_uploaded_file($file['tmp_name'], $destination)) {
        $response['success'] = true;
        $response['message'] = 'File uploaded successfully.';
        // Return the path relative to the project root with a cache-busting query string
        $response['path'] = 'data/images/backgrounds/' . $fileName . '?v=' . time();
    } else {
        http_response_code(500);
        $response['message'] = 'Failed to move uploaded file.';
    }

} else {
    http_response_code(400);
    switch ($_FILES['background']['error'] ?? UPLOAD_ERR_NO_FILE) {
        case UPLOAD_ERR_INI_SIZE:
        case UPLOAD_ERR_FORM_SIZE:
            $response['message'] = 'File is too large.';
            break;
        case UPLOAD_ERR_NO_FILE:
            $response['message'] = 'No file was uploaded.';
            break;
        default:
            $response['message'] = 'An error occurred during upload.';
            break;
    }
}

echo json_encode($response);