import {
    WebSocketGateway,
    WebSocketServer,
    OnGatewayInit,
    OnGatewayConnection,
    OnGatewayDisconnect,
    SubscribeMessage,
} from '@nestjs/websockets';
import { Server, Socket } from 'socket.io';
import { PrometheusService } from './prometheus.service';
import { Logger } from '@nestjs/common';

@WebSocketGateway({
    cors: {
        origin: process.env.FRONTEND_URL,
        methods: ['GET', 'POST'],
        credentials: true
    },
    namespace: '/api/metrics-ws'
})
export class MetricsGateway implements OnGatewayInit, OnGatewayConnection, OnGatewayDisconnect {
    @WebSocketServer() server: Server;
    private readonly logger = new Logger(MetricsGateway.name);
    private activeSockets: Map<string, Socket> = new Map();
    private metricSubscriptions = new Map<string, {
        stopUpdates: () => void;
        clients: Set<string>;
    }>();

    constructor(private readonly prometheusService: PrometheusService) { }

    afterInit(server: Server) {
        this.logger.log('WebSocket Gateway initialized');
    }

    handleConnection(client: Socket) {
        this.logger.log(`Client connected: ${client.id}`);
        this.activeSockets.set(client.id, client);
    }

    handleDisconnect(client: Socket) {
        this.logger.log(`Client disconnected: ${client.id}`);
        this.activeSockets.delete(client.id);

        // Очистка всех подписок этого клиента
        for (const [metric, subscription] of this.metricSubscriptions) {
            subscription.clients.delete(client.id);
            if (subscription.clients.size === 0) {
                subscription.stopUpdates();
                this.metricSubscriptions.delete(metric);
            }
        }
    }

    @SubscribeMessage('unsubscribe-all')
    handleUnsubscribeAll(client: Socket) {
        for (const [metric, subscription] of this.metricSubscriptions) {
            subscription.clients.delete(client.id);
            if (subscription.clients.size === 0) {
                subscription.stopUpdates();
                this.metricSubscriptions.delete(metric);
            }
        }
    }

    @SubscribeMessage('get-metrics')
    async handleGetMetrics(client: Socket, payload: any) {
        const { metric, start, end, step, isRangeQuery, requestId, filters = {} } = payload;

        if (!metric) {
            client.emit('metrics-error', {
                error: 'Metric name is required',
                requestId
            });
            return;
        }

        if (isRangeQuery) {
            try {
                const data = await this.prometheusService.fetchMetricsRange(metric, start, end, step, filters);
                client.emit('metrics-data', { metric, data, requestId });
                return;
            } catch (error) {
                client.emit('metrics-error', {
                    error: error.message,
                    requestId
                });
                return;
            }
        }

        try {
            const stopUpdates = await this.sendPeriodicUpdates(
                metric,
                step || 5000,
                (data) => {
                    client.emit('metrics-data', { metric, data, requestId });
                },
                filters
            );

            const cleanup = () => {
                stopUpdates();
                client.off('disconnect', cleanup);
                client.off('unsubscribe-metric', cleanup);
            };

            client.on('disconnect', cleanup);
            client.on('unsubscribe-metric', cleanup);

        } catch (error) {
            client.emit('metrics-error', {
                error: error.message,
                requestId
            });
        }
    }

    private getSubscriptionKey(metric: string, filters: Record<string, string>): string {
        // Создаём уникальный ключ на основе метрики и фильтров
        const filterKeys = Object.keys(filters).sort();
        const filterString = filterKeys.map(k => `${k}=${filters[k]}`).join('&');
        return `${metric}${filterString ? `?${filterString}` : ''}`;
    }

    @SubscribeMessage('subscribe-metric')
    async handleSubscribeMetric(
        client: Socket,
        payload: {
            metric: string;
            interval?: number;
            filters?: Record<string, string>;
        }
    ) {
        const { metric, interval = 5000, filters = {} } = payload;
        const subscriptionKey = this.getSubscriptionKey(metric, filters);

        if (!this.metricSubscriptions.has(subscriptionKey)) {
            const stopUpdates = await this.sendPeriodicUpdates(
                metric,
                interval,
                (data) => {
                    // Отправляем только подписчикам этой конкретной метрики с фильтрами
                    this.server.emit('metrics-data', {
                        metric: subscriptionKey,
                        data
                    });
                },
                filters
            );

            this.metricSubscriptions.set(subscriptionKey, {
                stopUpdates,
                clients: new Set([client.id])
            });
        } else {
            this.metricSubscriptions.get(subscriptionKey)?.clients.add(client.id);
        }

        const unsubscribe = () => {
            const subscription = this.metricSubscriptions.get(subscriptionKey);
            if (subscription) {
                subscription.clients.delete(client.id);
                if (subscription.clients.size === 0) {
                    subscription.stopUpdates();
                    this.metricSubscriptions.delete(subscriptionKey);
                }
            }
        };

        client.on('disconnect', unsubscribe);
        client.on('unsubscribe-metric', unsubscribe);
    }

    async sendPeriodicUpdates(
        metric: string,
        interval: number,
        callback: (data: any) => void,
        filters: Record<string, string> = {}
    ) {
        const timer = setInterval(async () => {
            try {
                const data = await this.prometheusService.fetchMetricsWithFilters(metric, filters);
                callback(data);
            } catch (error) {
                this.logger.error(`Error in periodic update for ${metric}:`, error.message);
            }
        }, interval);

        return () => {
            clearInterval(timer);
            this.logger.log(`Stopped updates for ${metric}`);
        };
    }
}