<?php
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

session_start();

$logFile = __DIR__ . '/error.log';
// Clear the log file for each request to ensure we're only seeing the latest error.
file_put_contents($logFile, ""); 

// This is the top-level error handler.
// It will catch any exception that isn't caught elsewhere.
set_exception_handler(function($exception) use ($logFile) {
    http_response_code(500);
    $error = [
        'error' => 'An unexpected error occurred.',
        'message' => $exception->getMessage(),
        'file' => $exception->getFile(),
        'line' => $exception->getLine(),
    ];
    file_put_contents($logFile, json_encode($error, JSON_PRETTY_PRINT));
    // We must output valid JSON, otherwise the frontend will get a syntax error.
    echo json_encode($error); 
});

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

// The main try-catch block for the application logic.
try {
    
    // Check if it's a POST request
    if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
        http_response_code(405); // Method Not Allowed
        throw new Exception('Only POST requests are allowed.');
    }

    // Get the user's message from the request body
    $json_data = file_get_contents('php://input');
    $data = json_decode($json_data);
    $user_message = $data->message ?? '';

    if (empty($user_message)) {
        http_response_code(400); // Bad Request
        throw new Exception('Message is required.');
    }

    // --- Database Interaction ---
    $pdo = db();
    if (empty($_SESSION['chat_session_id'])) {
        $_SESSION['chat_session_id'] = bin2hex(random_bytes(16));
    }
    $chat_session_id = $_SESSION['chat_session_id'];

    // Log the user's message
    $stmt = $pdo->prepare("INSERT INTO chat_log (session_id, sender, message) VALUES (?, ?, ?)");
    $stmt->execute([$chat_session_id, 'user', $user_message]);

    // --- OpenAI API Call ---
    $bot_response_data = OpenAIService::getCompletion($user_message);

    if (isset($bot_response_data['error'])) {
        throw new Exception('OpenAI API Error: ' . $bot_response_data['error']);
    }
    $bot_response = $bot_response_data['reply'];

    // Log the bot's response
    $stmt = $pdo->prepare("INSERT INTO chat_log (session_id, sender, message) VALUES (?, ?, ?)");
    $stmt->execute([$chat_session_id, 'bot', $bot_response]);
    
    // --- Send Response ---
    header('Content-Type: application/json');
    echo json_encode(['reply' => $bot_response]);

} catch (Throwable $e) {
    // This will catch both Exceptions and Errors
    http_response_code(500);
    $errorDetails = [
        'error' => 'Caught in main try-catch',
        'message' => $e->getMessage(),
        'file' => $e->getFile(),
        'line' => $e->getLine(),
        'trace' => $e->getTraceAsString()
    ];
    file_put_contents($logFile, date('Y-m-d H:i:s') . " - " . json_encode($errorDetails, JSON_PRETTY_PRINT) . "
", FILE_APPEND);
    // Ensure a JSON response is sent on error
    header('Content-Type: application/json');
    echo json_encode($errorDetails);
}