//go:generate ../../../tools/readme_config_includer/generator
package nomad

import (
	_ "embed"
	"encoding/json"
	"fmt"
	"net/http"
	"time"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/config"
	"github.com/influxdata/telegraf/internal"
	"github.com/influxdata/telegraf/plugins/common/tls"
	"github.com/influxdata/telegraf/plugins/inputs"
)

//go:embed sample.conf
var sampleConfig string

const timeLayout = "2006-01-02 15:04:05 -0700 MST"

type Nomad struct {
	URL             string          `toml:"url"`
	ResponseTimeout config.Duration `toml:"response_timeout"`
	tls.ClientConfig

	roundTripper http.RoundTripper
}

func (*Nomad) SampleConfig() string {
	return sampleConfig
}

func (n *Nomad) Init() error {
	if n.URL == "" {
		n.URL = "http://127.0.0.1:4646"
	}

	tlsCfg, err := n.ClientConfig.TLSConfig()
	if err != nil {
		return fmt.Errorf("setting up TLS configuration failed: %w", err)
	}

	n.roundTripper = &http.Transport{
		TLSHandshakeTimeout:   5 * time.Second,
		TLSClientConfig:       tlsCfg,
		ResponseHeaderTimeout: time.Duration(n.ResponseTimeout),
	}

	return nil
}

func (n *Nomad) Gather(acc telegraf.Accumulator) error {
	summaryMetrics := &metricsSummary{}
	err := n.loadJSON(n.URL+"/v1/metrics", summaryMetrics)
	if err != nil {
		return err
	}

	err = buildNomadMetrics(acc, summaryMetrics)
	if err != nil {
		return err
	}

	return nil
}

func (n *Nomad) loadJSON(url string, v interface{}) error {
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return err
	}

	resp, err := n.roundTripper.RoundTrip(req)
	if err != nil {
		return fmt.Errorf("error making HTTP request to %q: %w", url, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("%s returned HTTP status %s", url, resp.Status)
	}

	err = json.NewDecoder(resp.Body).Decode(v)
	if err != nil {
		return fmt.Errorf("error parsing json response: %w", err)
	}

	return nil
}

// buildNomadMetrics, it builds all the metrics and adds them to the accumulator)
func buildNomadMetrics(acc telegraf.Accumulator, summaryMetrics *metricsSummary) error {
	t, err := internal.ParseTimestamp(timeLayout, summaryMetrics.Timestamp, nil)
	if err != nil {
		return fmt.Errorf("error parsing time: %w", err)
	}

	for _, counters := range summaryMetrics.Counters {
		tags := counters.DisplayLabels

		fields := map[string]interface{}{
			"count": counters.Count,
			"rate":  counters.Rate,
			"sum":   counters.Sum,
			"sumsq": counters.SumSq,
			"min":   counters.Min,
			"max":   counters.Max,
			"mean":  counters.Mean,
		}
		acc.AddCounter(counters.Name, fields, tags, t)
	}

	for _, gauges := range summaryMetrics.Gauges {
		tags := gauges.DisplayLabels

		fields := map[string]interface{}{
			"value": gauges.Value,
		}

		acc.AddGauge(gauges.Name, fields, tags, t)
	}

	for _, points := range summaryMetrics.Points {
		tags := make(map[string]string)

		fields := map[string]interface{}{
			"value": points.Points,
		}

		acc.AddFields(points.Name, fields, tags, t)
	}

	for _, samples := range summaryMetrics.Samples {
		tags := samples.DisplayLabels

		fields := map[string]interface{}{
			"count":  samples.Count,
			"rate":   samples.Rate,
			"sum":    samples.Sum,
			"stddev": samples.Stddev,
			"sumsq":  samples.SumSq,
			"min":    samples.Min,
			"max":    samples.Max,
			"mean":   samples.Mean,
		}
		acc.AddCounter(samples.Name, fields, tags, t)
	}

	return nil
}

func init() {
	inputs.Add("nomad", func() telegraf.Input {
		return &Nomad{
			ResponseTimeout: config.Duration(5 * time.Second),
		}
	})
}