const express = require("express");
const cors = require("cors");
const WebSocket = require("ws");
const app = express();

const PORT_HTTP = 4005;
const PORT_WS = 4006;
const PUSHGATEWAY = "http://pushgateway:9091";

// --- HTTP server ---
app.use(cors({ origin: "*", methods: ["GET", "POST"], allowedHeaders: ["Content-Type"], credentials: true }));
app.use(express.json({ limit: "50mb" }));

app.post("/push", (req, res) => {
    const metric = req.body;
    if (metric) pushToProm(metric);
    res.send("ok");
});

// --- WS server ---
const wss = new WebSocket.Server({ port: PORT_WS });
wss.on("connection", ws => {
    console.log("New WS connection. Online users:", wss.clients.size);
    pushOnlineCount();

    ws.on("message", msg => {
        try {
            const m = JSON.parse(msg);
            pushToProm(m);
        } catch (e) {
            console.error("Invalid WS message:", e);
        }
    });

    ws.on("close", () => pushOnlineCount());
});

// --- Push metrics to Pushgateway ---
async function pushToProm(metric) {
    if (!metric || !metric.type) return;

    const lines = [];
    let job = "webapp"; // default job
    let groupingKey = {};

    switch (metric.type) {
        case "frontend_metrics":
            job = "webapp_frontend";

            lines.push(`# HELP frontend_load_time Frontend page load time in ms`);
            lines.push(`# TYPE frontend_load_time gauge`);
            lines.push(`frontend_load_time{instance="${metric.id || 'default'}"} ${metric.navigation?.loadEventEnd || 0}`);

            if (metric.memory?.usedJSHeapSize) {
                lines.push(`# HELP frontend_memory_used JS heap used in MB`);
                lines.push(`# TYPE frontend_memory_used gauge`);
                lines.push(`frontend_memory_used{instance="${metric.id || 'default'}"} ${metric.memory.usedJSHeapSize / 1024 / 1024}`);
            }

            if (metric.resources?.length) {
                lines.push(`# HELP frontend_resource_count Number of resources loaded`);
                lines.push(`# TYPE frontend_resource_count gauge`);
                lines.push(`frontend_resource_count{instance="${metric.id || 'default'}"} ${metric.resources.length}`);
            }

            break;

        case "rest":
            job = "webapp_api";
            lines.push(`# HELP rest_request_duration_ms REST request duration in ms`);
            lines.push(`# TYPE rest_request_duration_ms gauge`);
            lines.push(`rest_request_duration_ms{path="${metric.path}",status="${metric.status}"} ${metric.time}`);
            break;

        case "ws_in":
            job = "webapp_ws";
            lines.push(`# HELP ws_in_bytes_total WS bytes in`);
            lines.push(`# TYPE ws_in_bytes_total counter`);
            lines.push(`ws_in_bytes_total ${metric.length}`);
            break;

        case "ws_out":
            job = "webapp_ws";
            lines.push(`# HELP ws_out_bytes_total WS bytes out`);
            lines.push(`# TYPE ws_out_bytes_total counter`);
            lines.push(`ws_out_bytes_total ${metric.length}`);
            break;

        case "connection_status":
            job = "webapp_connection";
            lines.push(`# HELP users_online Users online`);
            lines.push(`# TYPE users_online gauge`);
            lines.push(`users_online ${metric.count || wss.clients.size}`);

            const putBody = lines.join("\n") + "\n";

            // Отправляем как PUT для Gauge, чтобы сбросить старые значения
            return await pushToPrometheus(`${PUSHGATEWAY}/metrics/job/${job}`, putBody, "PUT");
    }

    const body = lines.join("\n") + "\n";
    console.log(`Pushing metric for job=${job}:\n${body}\n`);

    // Используем POST по умолчанию для инкремента/добавления
    await pushToPrometheus(`${PUSHGATEWAY}/metrics/job/${job}`, body, "POST");
}

async function pushToPrometheus(url, body, method) {
    try {
        const response = await fetch(url, {
            method: method,
            headers: { "Content-Type": "text/plain" },
            body
        });
        if (response.status !== 200) {
            console.error(`PushGateway error (${method} ${url}):`, response.status, await response.text());
        }
    } catch (err) {
        console.error("PushGateway network error:", err.message);
    }
}


function pushOnlineCount() {
    pushToProm({ type: "connection_status", count: wss.clients.size });
}

// --- Start HTTP server ---
app.listen(PORT_HTTP, () => console.log("Metrics HTTP listening on", PORT_HTTP));
console.log("Metrics WS listening on", PORT_WS);

// Запуск интервала после инициализации wss
setInterval(pushOnlineCount, 5000);