<?php

/**
 * Ticket Dependencies API
 */

// Immediately set JSON header and start output buffering
ob_start();
header('Content-Type: application/json');

// Register shutdown function to catch fatal errors
register_shutdown_function(function () {
    $error = error_get_last();
    if ($error && in_array($error['type'], [E_ERROR, E_PARSE, E_CORE_ERROR, E_COMPILE_ERROR])) {
        // Log detailed error server-side
        error_log('Fatal error in ticket_dependencies.php: ' . $error['message'] . ' in ' . $error['file'] . ':' . $error['line']);
        ob_end_clean();
        http_response_code(500);
        header('Content-Type: application/json');
        echo json_encode([
            'success' => false,
            'error' => 'A server error occurred'
        ]);
    }
});

ini_set('display_errors', 0);
error_reporting(E_ALL);

// Custom error handler. Only genuine errors abort the request; notices,
// warnings and deprecations (e.g. new deprecations on a PHP upgrade) are
// logged but must not take the endpoint down with a 500.
set_error_handler(function ($errno, $errstr, $errfile, $errline) {
    // Respect the @-operator / error_reporting.
    if (!(error_reporting() & $errno)) {
        return false;
    }
    error_log("PHP Error in ticket_dependencies.php: $errstr in $errfile:$errline");
    if (!in_array($errno, [E_ERROR, E_USER_ERROR, E_RECOVERABLE_ERROR, E_PARSE], true)) {
        // Non-fatal: log and continue.
        return true;
    }
    ob_end_clean();
    http_response_code(500);
    header('Content-Type: application/json');
    echo json_encode([
        'success' => false,
        'error' => 'A server error occurred'
    ]);
    exit;
});

// Custom exception handler
set_exception_handler(function ($e) {
    // Log detailed error server-side
    error_log('Exception in ticket_dependencies.php: ' . $e->getMessage() . ' in ' . $e->getFile() . ':' . $e->getLine());
    ob_end_clean();
    http_response_code(500);
    header('Content-Type: application/json');
    echo json_encode([
        'success' => false,
        'error' => 'A server error occurred'
    ]);
    exit;
});

// Apply rate limiting (also starts session)
require_once dirname(__DIR__) . '/middleware/RateLimitMiddleware.php';
RateLimitMiddleware::apply('api');

// Ensure session is started
if (session_status() === PHP_SESSION_NONE) {
    session_start();
}

require_once dirname(__DIR__) . '/config/config.php';
require_once dirname(__DIR__) . '/helpers/Database.php';
require_once dirname(__DIR__) . '/services/DependencyService.php';
require_once dirname(__DIR__) . '/helpers/ResponseHelper.php';

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

// Check authentication
if (!isset($_SESSION['user']) || !isset($_SESSION['user']['user_id'])) {
    ResponseHelper::unauthorized();
}

$currentUser = $_SESSION['user'];

// CSRF Protection for POST/DELETE
if ($_SERVER['REQUEST_METHOD'] === 'POST' || $_SERVER['REQUEST_METHOD'] === 'DELETE') {
    require_once dirname(__DIR__) . '/middleware/CsrfMiddleware.php';
    $csrfToken = $_SERVER['HTTP_X_CSRF_TOKEN'] ?? '';
    if (!CsrfMiddleware::validateToken($csrfToken)) {
        ResponseHelper::error('Invalid CSRF token', 403, ['csrf_token' => CsrfMiddleware::getToken()]);
    }
}

// Use centralized database connection
$conn = Database::getConnection();

// Check if ticket_dependencies table exists
$tableCheck = $conn->query("SHOW TABLES LIKE 'ticket_dependencies'");
if ($tableCheck->num_rows === 0) {
    ResponseHelper::serverError('Ticket dependencies feature not available. The ticket_dependencies table does not exist. Please run the migration.');
}

$method = $_SERVER['REQUEST_METHOD'];

try {
    switch ($method) {
        case 'GET':
            // Get dependencies for a ticket
            $result = DependencyService::list($conn, $currentUser, $_GET['ticket_id'] ?? null);
            if (!$result['success']) {
                ResponseHelper::error($result['error'], $result['http_status']);
            }
            ResponseHelper::success([
                'dependencies' => $result['dependencies'],
                'dependents' => $result['dependents']
            ]);
            break;

        case 'POST':
            // Add a new dependency
            $data = json_decode(file_get_contents('php://input'), true);
            if (!is_array($data)) {
                ResponseHelper::error('Invalid JSON');
            }

            $result = DependencyService::add($conn, $currentUser, $data);
            if (!$result['success']) {
                ResponseHelper::error($result['error'], $result['http_status']);
            }
            ResponseHelper::created($result);
            break;

        case 'DELETE':
            // Remove a dependency, by dependency_id or by ticket IDs + type
            $data = json_decode(file_get_contents('php://input'), true);
            if (!is_array($data)) {
                ResponseHelper::error('Invalid JSON');
            }

            $result = DependencyService::remove($conn, $currentUser, $data);
            if (!$result['success']) {
                ResponseHelper::error($result['error'], $result['http_status']);
            }
            ResponseHelper::success([], 'Dependency removed');
            break;

        default:
            ResponseHelper::error('Method not allowed', 405);
    }
} catch (Exception $e) {
    // Log detailed error server-side
    error_log('Ticket dependencies API error: ' . $e->getMessage() . ' in ' . $e->getFile() . ':' . $e->getLine());
    ResponseHelper::serverError('An error occurred while processing the dependency request');
};