// LegacyDelete returns a handler that accepts delete requests. It deals with
// the deprecated API.
//
// The returned handler is already instrumented for Prometheus.
func LegacyDelete(ms storage.MetricStore) func(http.ResponseWriter, *http.Request, httprouter.Params) {
	var ps httprouter.Params
	var mtx sync.Mutex // Protects ps.

	instrumentedHandlerFunc := prometheus.InstrumentHandlerFunc(
		"delete",
		func(w http.ResponseWriter, _ *http.Request) {
			job := ps.ByName("job")
			instance := ps.ByName("instance")
			mtx.Unlock()

			if job == "" {
				http.Error(w, "job name is required", http.StatusBadRequest)
				return
			}
			labels := map[string]string{"job": job}
			if instance != "" {
				labels["instance"] = instance
			}
			ms.SubmitWriteRequest(storage.WriteRequest{
				Labels:    labels,
				Timestamp: time.Now(),
			})
			w.WriteHeader(http.StatusAccepted)
		},
	)

	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
		mtx.Lock()
		ps = params
		instrumentedHandlerFunc(w, r)
	}
}

// Delete returns a handler that accepts delete requests.
//
// The returned handler is already instrumented for Prometheus.
func Delete(ms storage.MetricStore) func(http.ResponseWriter, *http.Request, httprouter.Params) {
	var ps httprouter.Params
	var mtx sync.Mutex // Protects ps.

	instrumentedHandlerFunc := prometheus.InstrumentHandlerFunc(
		"delete",
		func(w http.ResponseWriter, _ *http.Request) {
			job := ps.ByName("job")
			labelsString := ps.ByName("labels")
			mtx.Unlock()

			labels, err := splitLabels(labelsString)
			if err != nil {
				http.Error(w, err.Error(), http.StatusBadRequest)
				return
			}
			if job == "" {
				http.Error(w, "job name is required", http.StatusBadRequest)
				return
			}
			labels["job"] = job
			ms.SubmitWriteRequest(storage.WriteRequest{
				Labels:    labels,
				Timestamp: time.Now(),
			})
			w.WriteHeader(http.StatusAccepted)
		},
	)
	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
		mtx.Lock()
		ps = params
		instrumentedHandlerFunc(w, r)
	}
}

// Status serves the status page.
func Status(
	ms storage.MetricStore,
	assetFunc func(string) ([]byte, error),
	flags map[string]string,
) func(http.ResponseWriter, *http.Request) {
	birth := time.Now()
	return func(w http.ResponseWriter, _ *http.Request) {
		t := template.New("status")
		t.Funcs(template.FuncMap{
			"value": func(f float64) string {
				return strconv.FormatFloat(f, 'f', -1, 64)
			},
		})
		tpl, err := assetFunc("template.html")
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		_, err = t.Parse(string(tpl))
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}

		buildInfo := map[string]string{
			"version":   version.Version,
			"revision":  version.Revision,
			"branch":    version.Branch,
			"buildUser": version.BuildUser,
			"buildDate": version.BuildDate,
			"goVersion": version.GoVersion,
		}

		d := &data{
			MetricGroups: ms.GetMetricFamiliesMap(),
			Flags:        flags,
			BuildInfo:    buildInfo,
			Birth:        birth,
		}
		err = t.Execute(w, d)
		if err != nil {
			// Hack to get a visible error message right at the top.
			fmt.Fprintf(w, `<div id="template-error" class="alert alert-danger">Error executing template: %s</div>`, html.EscapeString(err.Error()))
			fmt.Fprintln(w, `<script>$("#template-error").prependTo("body")</script>`)
		}
	}
}

// Push returns an http.Handler which accepts samples over HTTP and stores them
// in the MetricStore. If replace is true, all metrics for the job and instance
// given by the request are deleted before new ones are stored.
//
// The returned handler is already instrumented for Prometheus.
func Push(
	ms storage.MetricStore, replace bool,
) func(http.ResponseWriter, *http.Request, httprouter.Params) {
	var ps httprouter.Params
	var mtx sync.Mutex // Protects ps.

	instrumentedHandlerFunc := prometheus.InstrumentHandlerFunc(
		"push",
		func(w http.ResponseWriter, r *http.Request) {
			job := ps.ByName("job")
			labelsString := ps.ByName("labels")
			mtx.Unlock()

			labels, err := splitLabels(labelsString)
			if err != nil {
				http.Error(w, err.Error(), http.StatusBadRequest)
				return
			}
			if job == "" {
				http.Error(w, "job name is required", http.StatusBadRequest)
				return
			}
			labels["job"] = job

			if replace {
				ms.SubmitWriteRequest(storage.WriteRequest{
					Labels:    labels,
					Timestamp: time.Now(),
				})
			}

			var metricFamilies map[string]*dto.MetricFamily
			ctMediatype, ctParams, ctErr := mime.ParseMediaType(r.Header.Get("Content-Type"))
			if ctErr == nil && ctMediatype == "application/vnd.google.protobuf" &&
				ctParams["encoding"] == "delimited" &&
				ctParams["proto"] == "io.prometheus.client.MetricFamily" {
				metricFamilies = map[string]*dto.MetricFamily{}
				for {
					mf := &dto.MetricFamily{}
					if _, err = pbutil.ReadDelimited(r.Body, mf); err != nil {
						if err == io.EOF {
							err = nil
						}
						break
					}
					metricFamilies[mf.GetName()] = mf
				}
			} else {
				// We could do further content-type checks here, but the
				// fallback for now will anyway be the text format
				// version 0.0.4, so just go for it and see if it works.
				var parser text.Parser
				metricFamilies, err = parser.TextToMetricFamilies(r.Body)
			}
			if err != nil {
				http.Error(w, err.Error(), http.StatusInternalServerError)
				return
			}
			sanitizeLabels(metricFamilies, labels)
			ms.SubmitWriteRequest(storage.WriteRequest{
				Labels:         labels,
				Timestamp:      time.Now(),
				MetricFamilies: metricFamilies,
			})
			w.WriteHeader(http.StatusAccepted)
		},
	)

	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
		mtx.Lock()
		ps = params
		instrumentedHandlerFunc(w, r)
	}
}