<?php
require_once __DIR__ . '/../db/config.php';
require_once __DIR__ . '/../ai/LocalAIApi.php';

function telegramTableExists(string $table): bool
{
    static $cache = [];

    $table = strtolower($table);
    if (array_key_exists($table, $cache)) {
        return $cache[$table];
    }

    try {
        $stmt = db()->prepare("SELECT 1 FROM information_schema.TABLES WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = ? LIMIT 1");
        $stmt->execute([$table]);
        $cache[$table] = (bool)$stmt->fetchColumn();
    } catch (Throwable $e) {
        $cache[$table] = false;
    }

    return $cache[$table];
}

function telegramColumnExists(string $table, string $column): bool
{
    static $cache = [];

    $cacheKey = strtolower($table . '.' . $column);
    if (array_key_exists($cacheKey, $cache)) {
        return $cache[$cacheKey];
    }

    try {
        $stmt = db()->prepare("SELECT 1 FROM information_schema.COLUMNS WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = ? AND COLUMN_NAME = ? LIMIT 1");
        $stmt->execute([$table, $column]);
        $cache[$cacheKey] = (bool)$stmt->fetchColumn();
    } catch (Throwable $e) {
        $cache[$cacheKey] = false;
    }

    return $cache[$cacheKey];
}

function telegramSettingValue(string $key): ?string
{
    try {
        if (telegramColumnExists('settings', 'key') && telegramColumnExists('settings', 'value')) {
            $stmt = db()->prepare("SELECT `value` FROM settings WHERE `key` = ? LIMIT 1");
            $stmt->execute([$key]);
            $value = $stmt->fetchColumn();
            return $value === false ? null : (string)$value;
        }

        if (telegramColumnExists('settings', 'setting_key') && telegramColumnExists('settings', 'setting_value')) {
            $stmt = db()->prepare("SELECT setting_value FROM settings WHERE setting_key = ? LIMIT 1");
            $stmt->execute([$key]);
            $value = $stmt->fetchColumn();
            return $value === false ? null : (string)$value;
        }
    } catch (Throwable $e) {
        error_log('Telegram settings error: ' . $e->getMessage());
    }

    return null;
}

function telegramFetchFaqs(): array
{
    if (!telegramTableExists('faqs') || !telegramColumnExists('faqs', 'keywords') || !telegramColumnExists('faqs', 'answer')) {
        return [];
    }

    $stmt = db()->query("SELECT keywords, answer FROM faqs");
    return $stmt ? $stmt->fetchAll(PDO::FETCH_ASSOC) : [];
}

function telegramStoreMessage(string $userMessage, string $aiResponse): void
{
    if (!telegramTableExists('messages') || !telegramColumnExists('messages', 'user_message') || !telegramColumnExists('messages', 'ai_response')) {
        return;
    }

    try {
        $stmt = db()->prepare("INSERT INTO messages (user_message, ai_response) VALUES (?, ?)");
        $stmt->execute([$userMessage, $aiResponse]);
    } catch (Throwable $e) {
        error_log('Telegram DB Save Error: ' . $e->getMessage());
    }
}

function sendTelegramMessage($chatId, $text, $token)
{
    $url = "https://api.telegram.org/bot$token/sendMessage";
    $data = [
        'chat_id' => $chatId,
        'text' => $text,
        'parse_mode' => 'Markdown',
    ];

    $options = [
        'http' => [
            'header' => "Content-type: application/x-www-form-urlencoded
",
            'method' => 'POST',
            'content' => http_build_query($data),
        ],
    ];
    $context = stream_context_create($options);
    return file_get_contents($url, false, $context);
}

$content = file_get_contents('php://input');
$update = json_decode($content, true);

if (!$update || !isset($update['message'])) {
    exit;
}

$message = $update['message'];
$chatId = $message['chat']['id'] ?? null;
$text = $message['text'] ?? '';

if ($chatId === null || $text === '') {
    exit;
}

$token = telegramSettingValue('telegram_token');
if (!$token) {
    error_log('Telegram Error: No bot token found in settings.');
    exit;
}

try {
    $faqs = telegramFetchFaqs();

    $knowledgeBase = '';
    if ($faqs !== []) {
        $knowledgeBase = "Here is the knowledge base for this website:

";
        foreach ($faqs as $faq) {
            $knowledgeBase .= "Q: " . ($faq['keywords'] ?? '') . "
A: " . ($faq['answer'] ?? '') . "
---
";
        }
    }

    $systemPrompt = "You are a helpful AI assistant integrated with Telegram. " .
        "Use the provided Knowledge Base to answer user questions. " .
        "Keep answers concise for mobile reading. Use Markdown for formatting.

" .
        $knowledgeBase;

    $response = LocalAIApi::createResponse([
        'input' => [
            ['role' => 'system', 'content' => $systemPrompt],
            ['role' => 'user', 'content' => $text],
        ],
    ]);

    if (!empty($response['success'])) {
        $aiReply = LocalAIApi::extractText($response);
        telegramStoreMessage('[Telegram] ' . $text, $aiReply);
        sendTelegramMessage($chatId, $aiReply, $token);
    } else {
        sendTelegramMessage($chatId, "I'm sorry, I encountered an error processing your request.", $token);
    }
} catch (Throwable $e) {
    error_log('Telegram Webhook Error: ' . $e->getMessage());
}