<?php
header('Content-Type: application/json');
require_once __DIR__ . '/../db/config.php';
require_once __DIR__ . '/../ai/LocalAIApi.php';

function chatTableExists(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 chatColumnExists(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 chatFetchFaqs(): array
{
    if (!chatTableExists('faqs') || !chatColumnExists('faqs', 'keywords') || !chatColumnExists('faqs', 'answer')) {
        return [];
    }

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

function chatStoreMessage(string $userMessage, string $aiResponse): void
{
    if (!chatTableExists('messages') || !chatColumnExists('messages', 'user_message') || !chatColumnExists('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('DB Save Error: ' . $e->getMessage());
    }
}

$input = json_decode(file_get_contents('php://input'), true);
$message = $input['message'] ?? '';

if (empty($message)) {
    echo json_encode(['reply' => "I didn't catch that. Could you repeat?"]);
    exit;
}

try {
    $faqs = chatFetchFaqs();

    $knowledgeBase = '';
    if ($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, friendly AI assistant for this website. " .
        "Use the provided Knowledge Base to answer user questions accurately. " .
        "If the answer is found in the Knowledge Base, rephrase it naturally. " .
        "If the answer is NOT in the Knowledge Base, use your general knowledge to help, " .
        "but politely mention that you don't have specific information about that if it seems like a site-specific question. " .
        "Keep answers concise and professional.

" .
        $knowledgeBase;

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

    if (!empty($response['success'])) {
        $aiReply = LocalAIApi::extractText($response);
        chatStoreMessage($message, $aiReply);
        echo json_encode(['reply' => $aiReply]);
    } else {
        error_log('AI Error: ' . ($response['error'] ?? 'Unknown'));
        echo json_encode(['reply' => "I'm having trouble connecting to my brain right now. Please try again later."]);
    }
} catch (Throwable $e) {
    error_log('Chat Error: ' . $e->getMessage());
    echo json_encode(['reply' => 'An internal error occurred.']);
}