package observability

import (
	"fmt"
	"net/http"

	"github.com/prometheus/client_golang/prometheus/promhttp"
	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
)

// NewLogger creates a zap production logger at the given level.
func NewLogger(level string) (*zap.Logger, error) {
	cfg := zap.NewProductionConfig()
	lvl, err := zapcore.ParseLevel(level)
	if err != nil {
		lvl = zapcore.InfoLevel
	}
	cfg.Level = zap.NewAtomicLevelAt(lvl)
	return cfg.Build()
}

// ServeMetrics starts a Prometheus /metrics endpoint on the given port.
// It blocks until the server exits.
func ServeMetrics(port int) error {
	mux := http.NewServeMux()
	mux.Handle("/metrics", promhttp.Handler())
	mux.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte("ok"))
	})
	addr := fmt.Sprintf(":%d", port)
	return http.ListenAndServe(addr, mux)
}