package observability

import (
	"net/http"
)

// MetricsHandler serves Prometheus metrics
type MetricsHandler struct {
	exporter *PrometheusExporter
}

// NewMetricsHandler creates a new metrics handler
func NewMetricsHandler(m *Metrics) *MetricsHandler {
	return &MetricsHandler{
		exporter: NewPrometheusExporter(m),
	}
}

// ServeHTTP implements http.Handler for Prometheus /metrics endpoint
func (h *MetricsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain; version=0.0.4; charset=utf-8")
	w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
	w.Header().Set("Pragma", "no-cache")
	w.Header().Set("Expires", "0")

	w.WriteHeader(http.StatusOK)
	w.Write([]byte(h.exporter.Export()))
}