import { context, metrics, SpanStatusCode, trace } from "@opentelemetry/api";
import type { MiddlewareHandler } from "hono";

const tracer = trace.getTracer("processor.http");
const meter = metrics.getMeter("processor.http");

const requestCount = meter.createCounter("processor.http.server.requests", {
    description: "Total number of processor HTTP requests",
});

const requestDuration = meter.createHistogram(
    "processor.http.server.duration",
    {
        description: "Processor HTTP request duration",
        unit: "ms",
    },
);

const activeRequests = meter.createUpDownCounter(
    "processor.http.server.active_requests",
    {
        description: "Number of in-flight processor HTTP requests",
    },
);

export const httpTelemetryMiddleware: MiddlewareHandler = async (c, next) => {
    const startedAt = performance.now();
    const method = c.req.method;
    const route = c.req.path;

    const span = tracer.startSpan(`http ${method} ${route}`, {
        attributes: {
            "http.request.method": method,
            "url.path": route,
        },
    });

    activeRequests.add(1, {
        "http.request.method": method,
        "url.path": route,
    });

    try {
        await context.with(trace.setSpan(context.active(), span), next);

        span.setAttribute("http.response.status_code", c.res.status);
        span.setStatus({
            code:
                c.res.status >= 500
                    ? SpanStatusCode.ERROR
                    : SpanStatusCode.OK,
        });
    } catch (error) {
        span.recordException(error as Error);
        span.setStatus({
            code: SpanStatusCode.ERROR,
            message: "Unhandled processor request error",
        });
        throw error;
    } finally {
        const durationMs = performance.now() - startedAt;
        const attrs = {
            "http.request.method": method,
            "http.response.status_code": c.res.status,
            "url.path": route,
        };

        requestCount.add(1, attrs);
        requestDuration.record(durationMs, attrs);
        activeRequests.add(-1, {
            "http.request.method": method,
            "url.path": route,
        });

        span.end();
    }
};