<?php
/**
 * Server-Sent Events (SSE) Handler for Mobile App
 *
 * Provides real-time updates for queue state, incoming calls, and agent status
 */
class TWP_Mobile_SSE {

    private $auth;

    /**
     * Constructor
     */
    public function __construct() {
        require_once plugin_dir_path(__FILE__) . 'class-twp-mobile-auth.php';
        $this->auth = new TWP_Mobile_Auth();
    }

    /**
     * Register SSE endpoint
     */
    public function register_endpoints() {
        add_action('rest_api_init', function() {
            register_rest_route('twilio-mobile/v1', '/stream/events', array(
                'methods' => 'GET',
                'callback' => array($this, 'stream_events'),
                'permission_callback' => array($this->auth, 'verify_token')
            ));
        });
    }

    /**
     * Stream events to mobile app
     */
    public function stream_events($request) {
        $user_id = $this->auth->get_current_user_id();

        if (!$user_id) {
            return new WP_Error('unauthorized', 'Invalid token', array('status' => 401));
        }

        // Set headers for SSE
        header('Content-Type: text/event-stream');
        header('Cache-Control: no-cache');
        header('Connection: keep-alive');
        header('X-Accel-Buffering: no'); // Disable nginx buffering

        // Disable PHP output buffering
        if (function_exists('apache_setenv')) {
            @apache_setenv('no-gzip', '1');
        }
        @ini_set('zlib.output_compression', 0);
        @ini_set('implicit_flush', 1);
        ob_implicit_flush(1);
        while (ob_get_level() > 0) {
            ob_end_flush();
        }

        // Send initial connection event
        $this->send_event('connected', array('user_id' => $user_id, 'timestamp' => time()));

        // Get initial state
        $last_check = time();
        $previous_state = $this->get_current_state($user_id);

        // Stream loop - check for changes every 2 seconds
        $max_duration = 300; // 5 minutes max connection time
        $start_time = time();

        while (time() - $start_time < $max_duration) {
            // Check if connection is still alive
            if (connection_aborted()) {
                break;
            }

            // Get current state
            $current_state = $this->get_current_state($user_id);

            // Compare and send updates
            $this->check_and_send_updates($previous_state, $current_state);

            // Update previous state
            $previous_state = $current_state;

            // Send heartbeat every 15 seconds
            if (time() - $last_check >= 15) {
                $this->send_event('heartbeat', array('timestamp' => time()));
                $last_check = time();
            }

            // Sleep for 2 seconds
            sleep(2);
        }

        // Connection closing
        $this->send_event('disconnect', array('reason' => 'timeout', 'timestamp' => time()));
        exit;
    }

    /**
     * Get current state for agent
     */
    private function get_current_state($user_id) {
        global $wpdb;

        $state = array(
            'agent_status' => $this->get_agent_status($user_id),
            'queues' => $this->get_queues_state($user_id),
            'current_call' => $this->get_current_call($user_id)
        );

        return $state;
    }

    /**
     * Get agent status
     */
    private function get_agent_status($user_id) {
        global $wpdb;
        $table = $wpdb->prefix . 'twp_agent_status';

        $status = $wpdb->get_row($wpdb->prepare(
            "SELECT status, is_logged_in, current_call_sid FROM $table WHERE user_id = %d",
            $user_id
        ));

        if (!$status) {
            return array('status' => 'offline', 'is_logged_in' => false, 'current_call_sid' => null);
        }

        return array(
            'status' => $status->status,
            'is_logged_in' => (bool)$status->is_logged_in,
            'current_call_sid' => $status->current_call_sid
        );
    }

    /**
     * Get queues state
     */
    private function get_queues_state($user_id) {
        global $wpdb;
        $queues_table = $wpdb->prefix . 'twp_call_queues';
        $calls_table = $wpdb->prefix . 'twp_queued_calls';
        $assignments_table = $wpdb->prefix . 'twp_queue_assignments';

        // Get queue IDs
        $queue_ids = $wpdb->get_col($wpdb->prepare(
            "SELECT queue_id FROM $assignments_table WHERE user_id = %d",
            $user_id
        ));

        $personal_queue_ids = $wpdb->get_col($wpdb->prepare(
            "SELECT id FROM $queues_table WHERE user_id = %d",
            $user_id
        ));

        $all_queue_ids = array_unique(array_merge($queue_ids, $personal_queue_ids));

        if (empty($all_queue_ids)) {
            return array();
        }

        $queue_ids_str = implode(',', array_map('intval', $all_queue_ids));

        $queues = $wpdb->get_results("
            SELECT
                q.id,
                q.queue_name,
                COUNT(c.id) as waiting_count,
                MIN(c.enqueued_at) as oldest_call_time
            FROM $queues_table q
            LEFT JOIN $calls_table c ON q.id = c.queue_id AND c.status = 'waiting'
            WHERE q.id IN ($queue_ids_str)
            GROUP BY q.id
        ");

        $result = array();
        foreach ($queues as $queue) {
            $result[$queue->id] = array(
                'id' => (int)$queue->id,
                'name' => $queue->queue_name,
                'waiting_count' => (int)$queue->waiting_count,
                'oldest_call_time' => $queue->oldest_call_time
            );
        }

        return $result;
    }

    /**
     * Get current call for agent
     */
    private function get_current_call($user_id) {
        global $wpdb;
        $calls_table = $wpdb->prefix . 'twp_queued_calls';

        $agent_number = get_user_meta($user_id, 'twp_agent_phone', true);

        if (!$agent_number) {
            return null;
        }

        $call = $wpdb->get_row($wpdb->prepare(
            "SELECT call_sid, from_number, queue_id, status, joined_at
             FROM $calls_table
             WHERE agent_phone = %s AND status IN ('connecting', 'in_progress')
             ORDER BY joined_at DESC
             LIMIT 1",
            $agent_number
        ));

        if (!$call) {
            return null;
        }

        return array(
            'call_sid' => $call->call_sid,
            'from_number' => $call->from_number,
            'queue_id' => (int)$call->queue_id,
            'status' => $call->status,
            'duration' => time() - strtotime($call->joined_at)
        );
    }

    /**
     * Check state changes and send updates
     */
    private function check_and_send_updates($previous, $current) {
        // Check agent status changes
        if ($previous['agent_status'] !== $current['agent_status']) {
            $this->send_event('agent_status_changed', $current['agent_status']);
        }

        // Check queue changes
        $this->check_queue_changes($previous['queues'], $current['queues']);

        // Check current call changes
        if ($previous['current_call'] !== $current['current_call']) {
            if ($current['current_call'] && !$previous['current_call']) {
                // New call started
                $this->send_event('call_started', $current['current_call']);
            } elseif (!$current['current_call'] && $previous['current_call']) {
                // Call ended
                $this->send_event('call_ended', $previous['current_call']);
            } elseif ($current['current_call'] && $previous['current_call']) {
                // Call status changed
                if ($current['current_call']['status'] !== $previous['current_call']['status']) {
                    $this->send_event('call_status_changed', $current['current_call']);
                }
            }
        }
    }

    /**
     * Check for queue changes
     */
    private function check_queue_changes($previous_queues, $current_queues) {
        foreach ($current_queues as $queue_id => $current_queue) {
            $previous_queue = $previous_queues[$queue_id] ?? null;

            if (!$previous_queue) {
                // New queue added
                $this->send_event('queue_added', $current_queue);
                continue;
            }

            // Check for waiting count changes
            if ($current_queue['waiting_count'] !== $previous_queue['waiting_count']) {
                if ($current_queue['waiting_count'] > $previous_queue['waiting_count']) {
                    // New call in queue
                    $this->send_event('call_enqueued', array(
                        'queue_id' => $queue_id,
                        'queue_name' => $current_queue['name'],
                        'waiting_count' => $current_queue['waiting_count']
                    ));
                } else {
                    // Call removed from queue
                    $this->send_event('call_dequeued', array(
                        'queue_id' => $queue_id,
                        'queue_name' => $current_queue['name'],
                        'waiting_count' => $current_queue['waiting_count']
                    ));
                }
            }
        }

        // Check for removed queues
        foreach ($previous_queues as $queue_id => $previous_queue) {
            if (!isset($current_queues[$queue_id])) {
                $this->send_event('queue_removed', array('queue_id' => $queue_id));
            }
        }
    }

    /**
     * Send SSE event
     */
    private function send_event($event_type, $data) {
        echo "event: $event_type\n";
        echo "data: " . json_encode($data) . "\n\n";

        if (ob_get_level() > 0) {
            ob_flush();
        }
        flush();
    }
}