package metricsapi

import (
	"encoding/json"
	"net/http"

	"github.com/itworx/pulse/internal/auth"
	"github.com/itworx/pulse/internal/metriccatalog"
	"github.com/itworx/pulse/internal/problem"
)

type Handler struct{ Registry metriccatalog.Registry }

func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet || r.URL.Path != "/api/v1/metrics/catalog" {
		http.NotFound(w, r)
		return
	}
	if _, ok := auth.PrincipalFromContext(r.Context()); !ok {
		problem.Write(w, r, http.StatusUnauthorized, "UNAUTHORIZED", "Authentication required", "Authentication is required to read the metric catalog.", nil)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "private, max-age=60")
	w.Header().Set("ETag", `"`+h.Registry.Version()+`"`)
	if r.Header.Get("If-None-Match") == `"`+h.Registry.Version()+`"` {
		w.WriteHeader(http.StatusNotModified)
		return
	}
	if err := json.NewEncoder(w).Encode(h.Registry.Response()); err != nil {
		return
	}
}