<?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
set_error_handler(function($errno, $errstr, $errfile, $errline) {
    // Log detailed error server-side
    error_log("PHP Error in ticket_dependencies.php: $errstr in $errfile:$errline");
    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__) . '/models/DependencyModel.php';
require_once dirname(__DIR__) . '/models/AuditLogModel.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();
}

$userId = $_SESSION['user']['user_id'];

// 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::forbidden('Invalid CSRF token');
    }
}

// Create database connection
$conn = new mysqli(
    $GLOBALS['config']['DB_HOST'],
    $GLOBALS['config']['DB_USER'],
    $GLOBALS['config']['DB_PASS'],
    $GLOBALS['config']['DB_NAME']
);

if ($conn->connect_error) {
    ResponseHelper::serverError('Database connection failed');
}

// 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.');
}

try {
    $dependencyModel = new DependencyModel($conn);
    $auditLog = new AuditLogModel($conn);
} catch (Exception $e) {
    error_log('Failed to initialize models in ticket_dependencies.php: ' . $e->getMessage());
    ResponseHelper::serverError('Failed to initialize required components');
}

$method = $_SERVER['REQUEST_METHOD'];

try {
switch ($method) {
    case 'GET':
        // Get dependencies for a ticket
        $ticketId = $_GET['ticket_id'] ?? null;

        if (!$ticketId) {
            ResponseHelper::error('Ticket ID required');
        }

        try {
            $dependencies = $dependencyModel->getDependencies($ticketId);
            $dependents = $dependencyModel->getDependentTickets($ticketId);
        } catch (Exception $e) {
            error_log('Query error in ticket_dependencies.php GET: ' . $e->getMessage());
            ResponseHelper::serverError('Failed to retrieve dependencies');
        }

        ResponseHelper::success([
            'dependencies' => $dependencies,
            'dependents' => $dependents
        ]);
        break;

    case 'POST':
        // Add a new dependency
        $data = json_decode(file_get_contents('php://input'), true);

        $ticketId = $data['ticket_id'] ?? null;
        $dependsOnId = $data['depends_on_id'] ?? null;
        $type = $data['dependency_type'] ?? 'blocks';

        if (!$ticketId || !$dependsOnId) {
            ResponseHelper::error('Both ticket_id and depends_on_id are required');
        }

        $result = $dependencyModel->addDependency($ticketId, $dependsOnId, $type, $userId);

        if ($result['success']) {
            // Log to audit
            $auditLog->log($userId, 'create', 'dependency', (string)$result['dependency_id'], [
                'ticket_id' => $ticketId,
                'depends_on_id' => $dependsOnId,
                'type' => $type
            ]);

            ResponseHelper::created($result);
        } else {
            ResponseHelper::error($result['error']);
        }
        break;

    case 'DELETE':
        // Remove a dependency
        $data = json_decode(file_get_contents('php://input'), true);

        $dependencyId = $data['dependency_id'] ?? null;

        // Alternative: delete by ticket IDs
        if (!$dependencyId && isset($data['ticket_id']) && isset($data['depends_on_id'])) {
            $ticketId = $data['ticket_id'];
            $dependsOnId = $data['depends_on_id'];
            $type = $data['dependency_type'] ?? 'blocks';

            $result = $dependencyModel->removeDependencyByTickets($ticketId, $dependsOnId, $type);

            if ($result) {
                $auditLog->log($userId, 'delete', 'dependency', null, [
                    'ticket_id' => $ticketId,
                    'depends_on_id' => $dependsOnId,
                    'type' => $type
                ]);
                ResponseHelper::success([], 'Dependency removed');
            } else {
                ResponseHelper::error('Failed to remove dependency');
            }
        } elseif ($dependencyId) {
            $result = $dependencyModel->removeDependency($dependencyId);

            if ($result) {
                $auditLog->log($userId, 'delete', 'dependency', (string)$dependencyId);
                ResponseHelper::success([], 'Dependency removed');
            } else {
                ResponseHelper::error('Failed to remove dependency');
            }
        } else {
            ResponseHelper::error('Dependency ID or ticket IDs required');
        }
        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');
}

$conn->close();