package jolokia

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"strings"

	"github.com/influxdb/telegraf/plugins"
)

type Server struct {
	Name string
	Host string
	Port string
}

type Metric struct {
	Name string
	Jmx  string
	Pass []string
	Drop []string
}

type JolokiaClient interface {
	MakeRequest(req *http.Request) (*http.Response, error)
}

type JolokiaClientImpl struct {
	client *http.Client
}

func (c JolokiaClientImpl) MakeRequest(req *http.Request) (*http.Response, error) {
	return c.client.Do(req)
}

type Jolokia struct {
	jClient JolokiaClient
	Context string
	Servers []Server
	Metrics []Metric
	Tags    map[string]string
}

func (j *Jolokia) SampleConfig() string {
	return `
  # This is the context root used to compose the jolokia url
  context = "/jolokia/read"

  # Tags added to each measurements
  [jolokia.tags]
    group = "as"

  # List of servers exposing jolokia read service
  [[plugins.jolokia.servers]]
    name = "stable"
    host = "192.168.103.2"
    port = "8180"

  # List of metrics collected on above servers
  # Each metric consists in a name, a jmx path and either a pass or drop slice attributes
  # This collect all heap memory usage metrics
  [[plugins.jolokia.metrics]]
    name = "heap_memory_usage"
    jmx  = "/java.lang:type=Memory/HeapMemoryUsage"


  # This drops the 'committed' value from Eden space measurement
  [[plugins.jolokia.metrics]]
    name = "memory_eden"
    jmx  = "/java.lang:type=MemoryPool,name=PS Eden Space/Usage"
    drop = [ "committed" ]


  # This passes only DaemonThreadCount and ThreadCount
  [[plugins.jolokia.metrics]]
    name = "heap_threads"
    jmx  = "/java.lang:type=Threading"
    pass = [
      "DaemonThreadCount",
      "ThreadCount"
    ]
`
}

func (j *Jolokia) Description() string {
	return "Read JMX metrics through Jolokia"
}

func (j *Jolokia) getAttr(requestUrl *url.URL) (map[string]interface{}, error) {
	// Create + send request
	req, err := http.NewRequest("GET", requestUrl.String(), nil)
	if err != nil {
		return nil, err
	}

	resp, err := j.jClient.MakeRequest(req)
	if err != nil {
		return nil, err
	}

	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	// Process response
	if resp.StatusCode != http.StatusOK {
		err = fmt.Errorf("Response from url \"%s\" has status code %d (%s), expected %d (%s)",
			requestUrl,
			resp.StatusCode,
			http.StatusText(resp.StatusCode),
			http.StatusOK,
			http.StatusText(http.StatusOK))
		return nil, err
	}

	// read body
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}

	// Unmarshal json
	var jsonOut map[string]interface{}
	if err = json.Unmarshal([]byte(body), &jsonOut); err != nil {
		return nil, errors.New("Error decoding JSON response")
	}

	return jsonOut, nil
}

func (m *Metric) shouldPass(field string) bool {

	if m.Pass != nil {

		for _, pass := range m.Pass {
			if strings.HasPrefix(field, pass) {
				return true
			}
		}

		return false
	}

	if m.Drop != nil {

		for _, drop := range m.Drop {
			if strings.HasPrefix(field, drop) {
				return false
			}
		}

		return true
	}

	return true
}

func (m *Metric) filterFields(fields map[string]interface{}) map[string]interface{} {

	for field, _ := range fields {
		if !m.shouldPass(field) {
			delete(fields, field)
		}
	}

	return fields
}

func (j *Jolokia) Gather(acc plugins.Accumulator) error {

	context := j.Context //"/jolokia/read"
	servers := j.Servers
	metrics := j.Metrics
	tags := j.Tags

	if tags == nil {
		tags = map[string]string{}
	}

	for _, server := range servers {
		for _, metric := range metrics {

			measurement := metric.Name
			jmxPath := metric.Jmx

			tags["server"] = server.Name
			tags["port"] = server.Port
			tags["host"] = server.Host

			// Prepare URL
			requestUrl, err := url.Parse("http://" + server.Host + ":" + server.Port + context + jmxPath)
			if err != nil {
				return err
			}

			out, _ := j.getAttr(requestUrl)

			if values, ok := out["value"]; ok {
				switch values.(type) {
				case map[string]interface{}:
					acc.AddFields(measurement, metric.filterFields(values.(map[string]interface{})), tags)
				case interface{}:
					acc.Add(measurement, values.(interface{}), tags)
				}
			} else {
				fmt.Printf("Missing key 'value' in '%s' output response\n", requestUrl.String())
			}
		}
	}

	return nil
}

func init() {
	plugins.Add("jolokia", func() plugins.Plugin {
		return &Jolokia{jClient: &JolokiaClientImpl{client: &http.Client{}}}
	})
}