package librato

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/internal"
	"github.com/influxdata/telegraf/plugins/outputs"
	"github.com/influxdata/telegraf/plugins/serializers/graphite"
)

type Librato struct {
	ApiUser      string
	ApiToken     string
	Debug        bool
	NameFromTags bool
	SourceTag    string
	Timeout      internal.Duration
	Template     string

	apiUrl string
	client *http.Client
}

var sampleConfig = `
  ## Librator API Docs
  ## http://dev.librato.com/v1/metrics-authentication
  ## Librato API user
  api_user = "telegraf@influxdb.com" # required.
  ## Librato API token
  api_token = "my-secret-token" # required.
  ## Debug
  # debug = false
  ## Tag Field to populate source attribute (optional)
  ## This is typically the _hostname_ from which the metric was obtained.
  source_tag = "host"
  ## Connection timeout.
  # timeout = "5s"
  ## Output Name Template (same as graphite buckets)
  ## see https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_OUTPUT.md#graphite
  template = "host.tags.measurement.field"
`

type LMetrics struct {
	Gauges []*Gauge `json:"gauges"`
}

type Gauge struct {
	Name        string  `json:"name"`
	Value       float64 `json:"value"`
	Source      string  `json:"source"`
	MeasureTime int64   `json:"measure_time"`
}

const librato_api = "https://metrics-api.librato.com/v1/metrics"

func NewLibrato(apiUrl string) *Librato {
	return &Librato{
		apiUrl: apiUrl,
	}
}

func (l *Librato) Connect() error {
	if l.ApiUser == "" || l.ApiToken == "" {
		return fmt.Errorf("api_user and api_token are required fields for librato output")
	}
	l.client = &http.Client{
		Timeout: l.Timeout.Duration,
	}
	return nil
}

func (l *Librato) Write(metrics []telegraf.Metric) error {
	if len(metrics) == 0 {
		return nil
	}
	lmetrics := LMetrics{}
	tempGauges := []*Gauge{}
	metricCounter := 0

	for _, m := range metrics {
		if gauges, err := l.buildGauges(m); err == nil {
			for _, gauge := range gauges {
				tempGauges = append(tempGauges, gauge)
				metricCounter++
				if l.Debug {
					log.Printf("[DEBUG] Got a gauge: %v\n", gauge)
				}
			}
		} else {
			log.Printf("unable to build Gauge for %s, skipping\n", m.Name())
			if l.Debug {
				log.Printf("[DEBUG] Couldn't build gauge: %v\n", err)
			}
		}
	}

	lmetrics.Gauges = make([]*Gauge, metricCounter)
	copy(lmetrics.Gauges, tempGauges[0:])
	metricsBytes, err := json.Marshal(lmetrics)
	if err != nil {
		return fmt.Errorf("unable to marshal Metrics, %s\n", err.Error())
	} else {
		if l.Debug {
			log.Printf("[DEBUG] Librato request: %v\n", string(metricsBytes))
		}
	}
	req, err := http.NewRequest("POST", l.apiUrl, bytes.NewBuffer(metricsBytes))
	if err != nil {
		return fmt.Errorf("unable to create http.Request, %s\n", err.Error())
	}
	req.Header.Add("Content-Type", "application/json")
	req.SetBasicAuth(l.ApiUser, l.ApiToken)

	resp, err := l.client.Do(req)
	if err != nil {
		if l.Debug {
			log.Printf("[DEBUG] Error POSTing metrics: %v\n", err.Error())
		}
		return fmt.Errorf("error POSTing metrics, %s\n", err.Error())
	} else {
		if l.Debug {
			htmlData, err := ioutil.ReadAll(resp.Body)
			if err != nil {
				log.Printf("[DEBUG] Couldn't get response! (%v)\n", err)
			} else {
				log.Printf("[DEBUG] Librato response: %v\n", string(htmlData))
			}
		}
	}

	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		return fmt.Errorf("received bad status code, %d\n", resp.StatusCode)
	}

	return nil
}

func (l *Librato) SampleConfig() string {
	return sampleConfig
}

func (l *Librato) Description() string {
	return "Configuration for Librato API to send metrics to."
}

func (l *Librato) buildGauges(m telegraf.Metric) ([]*Gauge, error) {
	gauges := []*Gauge{}
	bucket := graphite.SerializeBucketName(m.Name(), m.Tags(), l.Template, "")
	for fieldName, value := range m.Fields() {
		gauge := &Gauge{
			Name:        graphite.InsertField(bucket, fieldName),
			MeasureTime: m.Time().Unix(),
		}
		if !gauge.verifyValue(value) {
			continue
		}
		if err := gauge.setValue(value); err != nil {
			return gauges, fmt.Errorf("unable to extract value from Fields, %s\n",
				err.Error())
		}
		if l.SourceTag != "" {
			if source, ok := m.Tags()[l.SourceTag]; ok {
				gauge.Source = source
			} else {
				return gauges,
					fmt.Errorf("undeterminable Source type from Field, %s\n",
						l.SourceTag)
			}
		}
		gauges = append(gauges, gauge)
	}
	if l.Debug {
		fmt.Printf("[DEBUG] Built gauges: %v\n", gauges)
	}
	return gauges, nil
}

func (g *Gauge) verifyValue(v interface{}) bool {
	switch v.(type) {
	case string:
		return false
	}
	return true
}

func (g *Gauge) setValue(v interface{}) error {
	switch d := v.(type) {
	case int:
		g.Value = float64(int(d))
	case int32:
		g.Value = float64(int32(d))
	case int64:
		g.Value = float64(int64(d))
	case float32:
		g.Value = float64(d)
	case float64:
		g.Value = float64(d)
	default:
		return fmt.Errorf("undeterminable type %+v", d)
	}
	return nil
}

func (l *Librato) Close() error {
	return nil
}

func init() {
	outputs.Add("librato", func() telegraf.Output {
		return NewLibrato(librato_api)
	})
}