<?php
declare(strict_types=1);

ini_set('display_errors', '1');
error_reporting(E_ALL);

$config = require __DIR__ . '/../../config/database.php';
$telegramConfig = require __DIR__ . '/../../config/telegram.php';
require_once __DIR__ . '/lib/message_footer.php';
require_once __DIR__ . '/lib/http.php';

$dsn = sprintf(
    'mysql:host=%s;dbname=%s;charset=%s',
    $config['host'],
    $config['dbname'],
    $config['charset'] ?? 'utf8mb4'
);

$pdo = new PDO(
    $dsn,
    $config['user'],
    $config['pass'],
    [
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
    ]
);

function telegramWebhookRespond(array $payload, int $statusCode = 200): never
{
    http_response_code($statusCode);
    header('Content-Type: application/json; charset=utf-8');
    echo json_encode($payload, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
    exit;
}

function telegramSendBotMessage(array $telegramConfig, string $chatId, string $messageText): void
{
    $botToken = trim((string) ($telegramConfig['bot_token'] ?? ''));
    if ($botToken === '' || $chatId === '' || $messageText === '') {
        return;
    }

    telegramHttpPostJson(
        'https://api.telegram.org/bot' . $botToken . '/sendMessage',
        [
            'chat_id' => $chatId,
            'text' => appendTelegramServiceFooter($messageText),
        ]
    );
}

$expectedSecret = trim((string) ($telegramConfig['webhook_secret'] ?? ''));
if ($expectedSecret !== '') {
    $providedSecret = (string) ($_SERVER['HTTP_X_TELEGRAM_BOT_API_SECRET_TOKEN'] ?? '');
    if (!hash_equals($expectedSecret, $providedSecret)) {
        telegramWebhookRespond(['ok' => false, 'error' => 'invalid_secret'], 403);
    }
}

$rawBody = file_get_contents('php://input');
$update = json_decode((string) $rawBody, true);
if (!is_array($update)) {
    telegramWebhookRespond(['ok' => false, 'error' => 'invalid_json'], 400);
}

$message = $update['message'] ?? $update['edited_message'] ?? null;
if (!is_array($message)) {
    telegramWebhookRespond(['ok' => true, 'status' => 'ignored_no_message']);
}

$chatId = isset($message['chat']['id']) ? (string) $message['chat']['id'] : '';
$telegramUsername = trim((string) ($message['from']['username'] ?? ''));
$text = trim((string) ($message['text'] ?? ''));

if ($chatId === '' || $text === '') {
    telegramWebhookRespond(['ok' => true, 'status' => 'ignored_missing_data']);
}

$token = null;
if (preg_match('/^\/start\s+connect_([A-Fa-f0-9]{32,128})$/', $text, $matches)) {
    $token = strtolower($matches[1]);
} elseif (preg_match('/^connect_([A-Fa-f0-9]{32,128})$/', $text, $matches)) {
    $token = strtolower($matches[1]);
}

if ($token === null) {
    telegramWebhookRespond(['ok' => true, 'status' => 'ignored_no_connect_token']);
}

$stmtUser = $pdo->prepare("
    SELECT `id`
    FROM `app_users`
    WHERE `telegram_link_token` = :token
      AND `telegram_link_token_expires_at` IS NOT NULL
      AND `telegram_link_token_expires_at` > NOW()
    LIMIT 1
");
$stmtUser->execute([':token' => $token]);
$user = $stmtUser->fetch();

if (!$user) {
    telegramWebhookRespond(['ok' => true, 'status' => 'token_not_found_or_expired']);
}

$stmtUpdate = $pdo->prepare("
    UPDATE `app_users`
    SET
        `telegram_username` = :telegram_username,
        `telegram_chat_id` = :telegram_chat_id,
        `telegram_connected_at` = NOW(),
        `telegram_link_token` = NULL,
        `telegram_link_token_expires_at` = NULL,
        `updated_at` = NOW()
    WHERE `id` = :id
");
$stmtUpdate->execute([
    ':telegram_username' => $telegramUsername !== '' ? $telegramUsername : null,
    ':telegram_chat_id' => $chatId,
    ':id' => (int) $user['id'],
]);

$welcomeName = $telegramUsername !== '' ? '@' . ltrim($telegramUsername, '@') : 'bei Telegram';
$welcomeMessage = implode("\n", [
    'Willkommen bei SkyView.',
    '',
    'Dein Telegram-Konto wurde erfolgreich mit deinem SkyView-Benutzer verbunden.',
    'Du kannst jetzt spaeter Hinweise und Inhalte direkt vom Bot erhalten.',
    '',
    'Verbunden als: ' . $welcomeName,
]);

telegramSendBotMessage($telegramConfig, $chatId, $welcomeMessage);

telegramWebhookRespond([
    'ok' => true,
    'status' => 'connected',
    'user_id' => (int) $user['id'],
]);