package influxdb

import (
	"errors"
	"fmt"
	"log"
	"math/rand"
	"net/url"
	"strings"
	"sync"
	"time"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/internal"
	"github.com/influxdata/telegraf/plugins/outputs"

	"github.com/influxdata/influxdb/client/v2"
)

type InfluxDB struct {
	// URL is only for backwards compatability
	URL              string
	URLs             []string `toml:"urls"`
	Username         string
	Password         string
	Database         string
	UserAgent        string
	RetentionPolicy  string
	WriteConsistency string
	Timeout          internal.Duration
	UDPPayload       int `toml:"udp_payload"`
	Downsampler      *Downsampling

	// Path to CA file
	SSLCA string `toml:"ssl_ca"`
	// Path to host cert file
	SSLCert string `toml:"ssl_cert"`
	// Path to cert key file
	SSLKey string `toml:"ssl_key"`
	// Use SSL but skip chain & host verification
	InsecureSkipVerify bool

	// Precision is only here for legacy support. It will be ignored.
	Precision string

	conns []client.Client
}

var sampleConfig = `
  ## The full HTTP or UDP endpoint URL for your InfluxDB instance.
  ## Multiple urls can be specified as part of the same cluster,
  ## this means that only ONE of the urls will be written to each interval.
  # urls = ["udp://localhost:8089"] # UDP endpoint example
  urls = ["http://localhost:8086"] # required
  ## The target database for metrics (telegraf will create it if not exists).
  database = "telegraf" # required

  ## Retention policy to write to. Empty string writes to the default rp.
  retention_policy = ""
  ## Write consistency (clusters only), can be: "any", "one", "quorum", "all"
  write_consistency = "any"

  ## Write timeout (for the InfluxDB client), formatted as a string.
  ## If not provided, will default to 5s. 0s means no timeout (not recommended).
  timeout = "5s"
  # username = "telegraf"
  # password = "metricsmetricsmetricsmetrics"
  ## Set the user agent for HTTP POSTs (can be useful for log differentiation)
  # user_agent = "telegraf"
  ## Set UDP payload size, defaults to InfluxDB UDP Client default (512 bytes)
  # udp_payload = 512

  ## Optional SSL Config
  # ssl_ca = "/etc/telegraf/ca.pem"
  # ssl_cert = "/etc/telegraf/cert.pem"
  # ssl_key = "/etc/telegraf/key.pem"
  ## Use SSL but skip chain & host verification
  # insecure_skip_verify = false
`

func (i *InfluxDB) Connect() error {
	var urls []string
	for _, u := range i.URLs {
		urls = append(urls, u)
	}

	// Backward-compatability with single Influx URL config files
	// This could eventually be removed in favor of specifying the urls as a list
	if i.URL != "" {
		urls = append(urls, i.URL)
	}

	tlsCfg, err := internal.GetTLSConfig(
		i.SSLCert, i.SSLKey, i.SSLCA, i.InsecureSkipVerify)
	if err != nil {
		return err
	}

	var conns []client.Client
	for _, u := range urls {
		switch {
		case strings.HasPrefix(u, "udp"):
			parsed_url, err := url.Parse(u)
			if err != nil {
				return err
			}

			if i.UDPPayload == 0 {
				i.UDPPayload = client.UDPPayloadSize
			}
			c, err := client.NewUDPClient(client.UDPConfig{
				Addr:        parsed_url.Host,
				PayloadSize: i.UDPPayload,
			})
			if err != nil {
				return err
			}
			conns = append(conns, c)
		default:
			// If URL doesn't start with "udp", assume HTTP client
			c, err := client.NewHTTPClient(client.HTTPConfig{
				Addr:      u,
				Username:  i.Username,
				Password:  i.Password,
				UserAgent: i.UserAgent,
				Timeout:   i.Timeout.Duration,
				TLSConfig: tlsCfg,
			})
			if err != nil {
				return err
			}

			err = createDatabase(c, i.Database)
			if err != nil {
				log.Println("Database creation failed: " + err.Error())
				continue
			}

			conns = append(conns, c)
		}
	}

	i.conns = conns
	rand.Seed(time.Now().UnixNano())
	return nil
}

func createDatabase(c client.Client, database string) error {
	// Create Database if it doesn't exist
	_, err := c.Query(client.Query{
		Command: fmt.Sprintf("CREATE DATABASE \"%s\"", database),
	})
	return err
}

func (i *InfluxDB) Close() error {
	var errS string
	for j, _ := range i.conns {
		if err := i.conns[j].Close(); err != nil {
			errS += err.Error()
		}
	}
	if errS != "" {
		return fmt.Errorf("output influxdb close failed: %s", errS)
	}
	return nil
}

func (i *InfluxDB) SampleConfig() string {
	return sampleConfig
}

func (i *InfluxDB) Description() string {
	return "Configuration for influxdb server to send metrics to"
}

func (i *InfluxDB) flush(bp client.BatchPoints) error {
	// This will get set to nil if a successful write occurs
	err := errors.New("Could not write to any InfluxDB server in cluster")
	p := rand.Perm(len(i.conns))
	for _, n := range p {
		if e := i.conns[n].Write(bp); e != nil {
			// Log write failure
			log.Printf("ERROR: %s", e)
			// If the database was not found, try to recreate it
			if strings.Contains(e.Error(), "database not found") {
				if errc := createDatabase(i.conns[n], i.Database); errc != nil {
					log.Printf("ERROR: Database %s not found and failed to recreate\n",
						i.Database)
				}
			}
		} else {
			err = nil
			break
		}
	}
	return err
}

// Choose a random server in the cluster to write to until a successful write
// occurs, logging each unsuccessful. If all servers fail, return error.
func (i *InfluxDB) Write(metrics []telegraf.Metric) error {
	if len(i.conns) == 0 {
		err := i.Connect()
		if err != nil {
			return err
		}
	}
	bp, err := i.batchPointsFromMetrics(metrics...)
	if err != nil {
		return err
	}

	i.Downsampler.Add(metrics...)
	err = i.flush(bp)
	return err
}

func (i *InfluxDB) batchPointsFromMetrics(metrics ...telegraf.Metric) (client.BatchPoints, error) {
	bp, err := client.NewBatchPoints(client.BatchPointsConfig{
		Database:         i.Database,
		RetentionPolicy:  i.RetentionPolicy,
		WriteConsistency: i.WriteConsistency,
	})
	if err != nil {
		return bp, err
	}

	for _, metric := range metrics {
		bp.AddPoint(metric.Point())
	}

	return bp, nil
}

func (i *InfluxDB) Run() {
	tick := time.Tick(i.Downsampler.TimeRange)
	for {
		select {
		case <-tick:
			aggrData, err := i.Downsampler.Aggregate()
			if err != nil {
				continue
			}

			i.Downsampler.Lock()
			i.Downsampler.Metrics = nil
			i.Downsampler.Unlock()

			if len(i.conns) == 0 {
				err := i.Connect()
				if err != nil {
					return
				}
			}

			bp, err := i.batchPointsFromMetrics(aggrData)
			if err != nil {
				return
			}

			err = i.flush(bp)
			if err != nil {
				return
			}
		}
	}
}

func init() {
	influxdb := &InfluxDB{
		Timeout: internal.Duration{Duration: time.Second * 5},
		Downsampler: &Downsampling{
			TimeRange: time.Duration(time.Minute * 2),
		},
	}
	go influxdb.Run()
	outputs.Add("influxdb", func() telegraf.Output {
		return influxdb
	})
}

// Downsampling
type Downsampling struct {
	sync.RWMutex
	Name         string
	Metrics      []telegraf.Metric
	TimeRange    time.Duration
	Aggregations map[string][]Aggregation
}

func NewDownsampling(name string, timeRange time.Duration) *Downsampling {
	return &Downsampling{
		Name:         name,
		TimeRange:    timeRange,
		Aggregations: make(map[string][]Aggregation),
	}
}

// Aggregation maps the field names to aggregation function for them
type Aggregation struct {
	FieldName string
	FuncName  string
	Alias     string
}

func (d *Downsampling) AddAggregations(aggrs ...Aggregation) {
	if d.Aggregations == nil {
		d.Aggregations = make(map[string][]Aggregation)
	}

	for _, aggr := range aggrs {
		switch aggr.FuncName {
		case "mean":
			d.Aggregations["mean"] = append(d.Aggregations["mean"], aggr)
		case "sum":
			d.Aggregations["sum"] = append(d.Aggregations["sum"], aggr)
		default:
		}
	}
}

// Add appends metrics to the metrics that will be aggregated
func (d *Downsampling) Add(metrics ...telegraf.Metric) {
	d.Lock()
	d.Metrics = append(d.Metrics, metrics...)
	d.Unlock()
	return
}

// Aggregate calculates the mean value of fields by given time
func (d *Downsampling) Aggregate() (telegraf.Metric, error) {
	metrics := map[string]interface{}{}
	var (
		aggrMetric, sum, mean telegraf.Metric
		err                   error
	)
	for name, aggr := range d.Aggregations {
		switch name {
		case "sum":
			sum, err = d.Sum(aggr...)
			if err != nil {
				return aggrMetric, err
			}
		case "mean":
			mean, err = d.Mean(aggr...)
			if err != nil {
				return aggrMetric, err
			}
		default:
		}
	}

	if sum != nil && sum.Fields() != nil {
		for k, v := range sum.Fields() {
			metrics[k] = v
		}
	}

	if mean != nil && mean.Fields() != nil {
		for k, v := range mean.Fields() {
			metrics[k] = v
		}
	}

	aggrMetric, err = telegraf.NewMetric(
		d.Name,
		map[string]string{},
		metrics,
		time.Now(),
	)
	return aggrMetric, err
}

// Sum calculate the sum values of given fields
func (d *Downsampling) Sum(fields ...Aggregation) (telegraf.Metric, error) {
	var (
		sumMetric telegraf.Metric
		sums      = make(map[string]interface{})
	)

	d.RLock()
	for _, metric := range d.Metrics {
		for _, field := range fields {
			value, ok := metric.Fields()[field.FieldName]
			if !ok {
				continue
			}

			oldVal, ok := sums[field.Alias]
			if !ok {
				sums[field.Alias] = value
				continue
			}

			switch value := value.(type) {
			case int:
				sums[field.Alias] = oldVal.(int) + int(value)
			case int32:
				sums[field.Alias] = oldVal.(int32) + int32(value)
			case int64:
				sums[field.Alias] = oldVal.(int64) + int64(value)
			case float32:
				sums[field.Alias] = oldVal.(float32) + float32(value)
			case float64:
				sums[field.Alias] = oldVal.(float64) + float64(value)
			default:
				continue
			}
		}
	}
	d.RUnlock()

	sumMetric, err := telegraf.NewMetric(
		d.Name,
		map[string]string{},
		sums,
		time.Now(),
	)
	return sumMetric, err
}

// Mean calculates the mean values of given fields
func (d *Downsampling) Mean(fields ...Aggregation) (telegraf.Metric, error) {
	var (
		aggrMetric telegraf.Metric
		sums       = make(map[string]interface{})
	)

	d.RLock()
	var size = len(d.Metrics)
	for _, metric := range d.Metrics {
		for _, field := range fields {
			value, ok := metric.Fields()[field.FieldName]
			if !ok {
				continue
			}

			oldVal, ok := sums[field.Alias]
			if !ok {
				sums[field.Alias] = value
				continue
			}

			switch value := value.(type) {
			case int:
				sums[field.Alias] = oldVal.(int) + int(value)
			case int32:
				sums[field.Alias] = oldVal.(int32) + int32(value)
			case int64:
				sums[field.Alias] = oldVal.(int64) + int64(value)
			case float32:
				sums[field.Alias] = oldVal.(float32) + float32(value)
			case float64:
				sums[field.Alias] = oldVal.(float64) + float64(value)
			default:
				continue
			}
		}
	}
	d.RUnlock()

	for i := range sums {
		switch value := sums[i].(type) {
		case int:
			sums[i] = value / int(size)
		case int32:
			sums[i] = value / int32(size)
		case int64:
			sums[i] = value / int64(size)
		case float32:
			sums[i] = value / float32(size)
		case float64:
			sums[i] = value / float64(size)
		default:
			continue
		}
	}

	aggrMetric, err := telegraf.NewMetric(
		d.Name,
		map[string]string{},
		sums,
		time.Now(),
	)
	return aggrMetric, err
}