<?php

/**
 * Recurring Tickets Management API
 * CRUD operations for recurring_tickets table
 */

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

require_once dirname(__DIR__) . '/middleware/RateLimitMiddleware.php';
RateLimitMiddleware::apply('api');

try {
    require_once dirname(__DIR__) . '/config/config.php';
    require_once dirname(__DIR__) . '/helpers/Database.php';
    require_once dirname(__DIR__) . '/models/RecurringTicketModel.php';
    require_once dirname(__DIR__) . '/models/AuditLogModel.php';

    // Check authentication
    if (session_status() === PHP_SESSION_NONE) {
        session_start();
    }
    if (!isset($_SESSION['user']) || !isset($_SESSION['user']['user_id'])) {
        http_response_code(401);
        echo json_encode(['success' => false, 'error' => 'Authentication required']);
        exit;
    }

    // Check admin privileges
    if (!$_SESSION['user']['is_admin']) {
        http_response_code(403);
        echo json_encode(['success' => false, 'error' => 'Admin privileges required']);
        exit;
    }

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

    // CSRF Protection for write operations
    if ($_SERVER['REQUEST_METHOD'] !== 'GET') {
        require_once dirname(__DIR__) . '/middleware/CsrfMiddleware.php';
        $csrfToken = $_SERVER['HTTP_X_CSRF_TOKEN'] ?? '';
        if (!CsrfMiddleware::validateToken($csrfToken)) {
            http_response_code(403);
            echo json_encode(['success' => false, 'error' => 'Invalid CSRF token']);
            exit;
        }
    }

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

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

    $model = new RecurringTicketModel($conn);
    $auditLog = new AuditLogModel($conn);
    $method = $_SERVER['REQUEST_METHOD'];
    $id = isset($_GET['id']) ? (int)$_GET['id'] : null;
    $action = isset($_GET['action']) ? $_GET['action'] : null;

    switch ($method) {
        case 'GET':
            if ($id) {
                $recurring = $model->getById($id);
                echo json_encode(['success' => (bool)$recurring, 'recurring' => $recurring]);
            } else {
                $all = $model->getAll(true);
                echo json_encode(['success' => true, 'recurring_tickets' => $all]);
            }
            break;

        case 'POST':
            if ($action === 'toggle' && $id) {
                $result = $model->toggleActive($id);
                if (!empty($result['success'])) {
                    $auditLog->log($currentUserId, 'update', 'recurring_ticket', (string)$id, [
                        'entity' => 'recurring_ticket',
                        'action' => 'toggle_active'
                    ]);
                }
                echo json_encode($result);
            } else {
                $data = json_decode(file_get_contents('php://input'), true);
                if (!is_array($data) || empty($data['schedule_type']) || empty($data['title_template'])) {
                    echo json_encode(['success' => false, 'error' => 'schedule_type and title_template are required']);
                    exit;
                }

                // Calculate next run time
                $nextRun = calculateNextRun(
                    $data['schedule_type'],
                    $data['schedule_day'] ?? null,
                    $data['schedule_time'] ?? '09:00'
                );

                $data['next_run_at'] = $nextRun;
                $data['is_active'] = isset($data['is_active']) ? (int)$data['is_active'] : 1;
                $data['created_by'] = $currentUserId;

                $result = $model->create($data);
                if (!empty($result['success'])) {
                    $auditLog->log($currentUserId, 'create', 'recurring_ticket', (string)($result['recurring_id'] ?? ''), [
                        'title_template' => $data['title_template'],
                        'schedule_type' => $data['schedule_type'],
                        'schedule_day' => $data['schedule_day'] ?? null,
                        'schedule_time' => $data['schedule_time'] ?? '09:00'
                    ]);
                }
                echo json_encode($result);
            }
            break;

        case 'PUT':
            if (!$id) {
                echo json_encode(['success' => false, 'error' => 'ID required']);
                exit;
            }

            $data = json_decode(file_get_contents('php://input'), true);
            if (!is_array($data) || empty($data['schedule_type'])) {
                echo json_encode(['success' => false, 'error' => 'Invalid request data']);
                exit;
            }

            $existing = $model->getById($id);
            if (!$existing) {
                echo json_encode(['success' => false, 'error' => 'Recurring ticket not found']);
                exit;
            }

            $newDay  = $data['schedule_day'] ?? null;
            $newTime = $data['schedule_time'] ?? '09:00';

            // Only the schedule fields affect when the next occurrence fires.
            $scheduleChanged =
                (string)$existing['schedule_type'] !== (string)$data['schedule_type']
                || (string)($existing['schedule_day'] ?? '') !== (string)($newDay ?? '')
                || substr((string)$existing['schedule_time'], 0, 5) !== substr((string)$newTime, 0, 5);

            $existingNextFuture = !empty($existing['next_run_at'])
                && strtotime($existing['next_run_at']) > time();

            // Recompute only when the schedule actually changed (or the stored
            // next_run is already in the past). Editing an unrelated field (e.g.
            // title) must NOT move next_run_at backwards past an occurrence that
            // may already have fired, which would double-create a ticket.
            if ($scheduleChanged || !$existingNextFuture) {
                $data['next_run_at'] = calculateNextRun(
                    $data['schedule_type'],
                    $newDay,
                    $newTime
                );
            } else {
                $data['next_run_at'] = $existing['next_run_at'];
            }
            $data['is_active'] = isset($data['is_active']) ? (int)$data['is_active'] : 1;

            $result = $model->update($id, $data);
            if (!empty($result['success'])) {
                $auditLog->log($currentUserId, 'update', 'recurring_ticket', (string)$id, [
                    'entity' => 'recurring_ticket',
                    'title_template' => $data['title_template'] ?? null,
                    'schedule_type' => $data['schedule_type'],
                    'schedule_day' => $newDay,
                    'schedule_time' => $newTime
                ]);
            }
            echo json_encode($result);
            break;

        case 'DELETE':
            if (!$id) {
                echo json_encode(['success' => false, 'error' => 'ID required']);
                exit;
            }

            $toDelete = $model->getById($id);
            $result = $model->delete($id);
            if (!empty($result['success'])) {
                $auditLog->log($currentUserId, 'delete', 'recurring_ticket', (string)$id, [
                    'entity' => 'recurring_ticket',
                    'title_template' => $toDelete['title_template'] ?? 'unknown'
                ]);
            }
            echo json_encode($result);
            break;

        default:
            http_response_code(405);
            echo json_encode(['success' => false, 'error' => 'Method not allowed']);
    }
} catch (Exception $e) {
    error_log("Recurring tickets API error: " . $e->getMessage());
    http_response_code(500);
    echo json_encode(['success' => false, 'error' => 'An internal error occurred']);
}

/**
 * Compute the SOONEST FUTURE occurrence matching the schedule.
 *
 * Returns 'Y-m-d H:i:s' in the app-configured timezone. The current period is
 * NOT skipped: a schedule whose time today/this-month is still in the future
 * fires then, not one period later.
 *
 * @param string        $scheduleType daily|weekly|monthly
 * @param int|null      $scheduleDay  1-7 (ISO, 1=Mon..7=Sun) weekly; 1-31 monthly
 * @param string        $scheduleTime HH:MM or HH:MM:SS
 * @param DateTime|null $now          Injected "now" for testing
 */
function calculateNextRun($scheduleType, $scheduleDay, $scheduleTime, ?DateTime $now = null)
{
    $tz = new DateTimeZone($GLOBALS['config']['TIMEZONE'] ?? date_default_timezone_get());
    $now = $now ? $now : new DateTime('now', $tz);

    $parts  = explode(':', $scheduleTime ?: '09:00');
    $hour   = (int)($parts[0] ?? 9);
    $minute = (int)($parts[1] ?? 0);
    $second = (int)($parts[2] ?? 0);

    $next = clone $now;

    switch ($scheduleType) {
        case 'weekly':
            $targetDow = (int)$scheduleDay;
            if ($targetDow < 1 || $targetDow > 7) {
                $targetDow = 1;
            }
            $next->setTime($hour, $minute, $second);
            $currentDow = (int)$next->format('N'); // 1=Mon .. 7=Sun
            $daysAhead = ($targetDow - $currentDow + 7) % 7;
            // Same weekday but the time already passed today -> next week.
            if ($daysAhead === 0 && $next <= $now) {
                $daysAhead = 7;
            }
            if ($daysAhead > 0) {
                $next->modify("+{$daysAhead} day");
                $next->setTime($hour, $minute, $second);
            }
            break;

        case 'monthly':
            $day = max(1, min(31, (int)$scheduleDay));
            // This month first, clamped to the month's length (e.g. day 31 -> Feb 28/29).
            $daysInMonth = (int)$now->format('t');
            $next->setDate((int)$now->format('Y'), (int)$now->format('n'), min($day, $daysInMonth));
            $next->setTime($hour, $minute, $second);
            if ($next <= $now) {
                // Already passed this month -> first day of next month, then clamp.
                $firstNext = clone $now;
                $firstNext->modify('first day of next month');
                $daysInMonth = (int)$firstNext->format('t');
                $next->setDate(
                    (int)$firstNext->format('Y'),
                    (int)$firstNext->format('n'),
                    min($day, $daysInMonth)
                );
                $next->setTime($hour, $minute, $second);
            }
            break;

        case 'daily':
        default:
            $next->setTime($hour, $minute, $second);
            if ($next <= $now) {
                $next->modify('+1 day');
                $next->setTime($hour, $minute, $second);
            }
            break;
    }

    return $next->format('Y-m-d H:i:s');
}