package exec

import (
	"bytes"
	"encoding/json"
	"fmt"
	"os/exec"
	"time"

	"github.com/gonuts/go-shellquote"

	"github.com/influxdata/telegraf"
	"github.com/influxdata/telegraf/internal"
	"github.com/influxdata/telegraf/plugins/inputs"
)

const sampleConfig = `
  # the command to run
  command = "/usr/bin/mycollector --foo=bar"

  # Data format to consume. This can be "json" or "influx" (line-protocol)
  # NOTE json only reads numerical measurements, strings and booleans are ignored.
  data_format = "json"

  # measurement name suffix (for separating different commands)
  name_suffix = "_mycollector"
`

type Exec struct {
	Command    string
	DataFormat string

	runner Runner
}

type Runner interface {
	Run(*Exec) ([]byte, error)
}

type CommandRunner struct{}

func (c CommandRunner) Run(e *Exec) ([]byte, error) {
	split_cmd, err := shellquote.Split(e.Command)
	if err != nil || len(split_cmd) == 0 {
		return nil, fmt.Errorf("exec: unable to parse command, %s", err)
	}

	cmd := exec.Command(split_cmd[0], split_cmd[1:]...)
	var out bytes.Buffer
	cmd.Stdout = &out

	if err := cmd.Run(); err != nil {
		return nil, fmt.Errorf("exec: %s for command '%s'", err, e.Command)
	}

	return out.Bytes(), nil
}

func NewExec() *Exec {
	return &Exec{runner: CommandRunner{}}
}

func (e *Exec) SampleConfig() string {
	return sampleConfig
}

func (e *Exec) Description() string {
	return "Read flattened metrics from one or more commands that output JSON to stdout"
}

func (e *Exec) Gather(acc telegraf.Accumulator) error {
	out, err := e.runner.Run(e)
	if err != nil {
		return err
	}

	switch e.DataFormat {
	case "", "json":
		var jsonOut interface{}
		err = json.Unmarshal(out, &jsonOut)
		if err != nil {
			return fmt.Errorf("exec: unable to parse output of '%s' as JSON, %s",
				e.Command, err)
		}

		f := internal.JSONFlattener{}
		err = f.FlattenJSON("", jsonOut)
		if err != nil {
			return err
		}
		acc.AddFields("exec", f.Fields, nil)
	case "influx":
		now := time.Now()
		metrics, err := telegraf.NewMetricParser().Parse(out)
		for _, metric := range metrics {
			acc.AddFields(metric.Name(), metric.Fields(), metric.Tags(), now)
		}
		return err
	default:
		return fmt.Errorf("Unsupported data format: %s. Must be either json "+
			"or influx.", e.DataFormat)
	}
	return nil
}

func init() {
	inputs.Add("exec", func() telegraf.Input {
		return NewExec()
	})
}