package collector

import (
	"fmt"

	"github.com/elastic/beats/libbeat/common"
	"github.com/elastic/beats/libbeat/common/cfgwarn"
	"github.com/elastic/beats/metricbeat/helper"
	"github.com/elastic/beats/metricbeat/mb"
	"github.com/elastic/beats/metricbeat/mb/parse"
)

const (
	defaultScheme = "http"
	defaultPath   = "/metrics"
)

var (
	hostParser = parse.URLHostParserBuilder{
		DefaultScheme: defaultScheme,
		DefaultPath:   defaultPath,
		PathConfigKey: "metrics_path",
	}.Build()
)

func init() {
	if err := mb.Registry.AddMetricSet("prometheus", "collector", New, hostParser); err != nil {
		panic(err)
	}
}

type MetricSet struct {
	mb.BaseMetricSet
	prometheus *helper.Prometheus
	namespace  string
}

func New(base mb.BaseMetricSet) (mb.MetricSet, error) {
	cfgwarn.Beta("The prometheus collector metricset is beta")

	config := struct {
		Namespace string `config:"namespace" validate:"required"`
	}{}
	err := base.Module().UnpackConfig(&config)
	if err != nil {
		return nil, err
	}

	return &MetricSet{
		BaseMetricSet: base,
		prometheus:    helper.NewPrometheusClient(base),
		namespace:     config.Namespace,
	}, nil
}

func (m *MetricSet) Fetch() ([]common.MapStr, error) {
	families, err := m.prometheus.GetFamilies()

	if err != nil {
		return nil, fmt.Errorf("Unable to decode response from prometheus endpoint")
	}

	eventList := map[string]common.MapStr{}

	for _, family := range families {
		promEvents := GetPromEventsFromMetricFamily(family)

		for _, promEvent := range promEvents {
			if _, ok := eventList[promEvent.labelHash]; !ok {
				eventList[promEvent.labelHash] = common.MapStr{}

				// Add labels
				if len(promEvent.labels) > 0 {
					eventList[promEvent.labelHash]["label"] = promEvent.labels
				}
			}

			eventList[promEvent.labelHash][promEvent.key] = promEvent.value
		}
	}

	// Converts hash list to slice
	events := []common.MapStr{}
	for _, e := range eventList {
		e[mb.NamespaceKey] = m.namespace
		events = append(events, e)
	}

	return events, err
}