package svej

import (
  "log"
  "time"
  "strconv"
  "strings"
  "fmt"
  "github.com/oliveagle/jsonpath"
  "encoding/json"
  "udi/config"
  "udi/handlers/handler"
  "udi/database"
)

var idSeq int = 0

type SingleValueExtractorJsonpathHandler struct {
  id int
  ready bool
  application string
  deviceSelector string
  valueSelector string
  unitSelector string
  deviceJsonpath *jsonpath.Compiled
  valueJsonpath *jsonpath.Compiled
  unitJsonpath *jsonpath.Compiled
  dbh *database.DatabaseHandle
}

/*
Valid values for selectors:
J:JsonpathExpression
T:TopicPartIndex
C:ConstantValue
*/


func NewSvejHandler(config config.HandlerConfigT) handler.Handler {
  t := &SingleValueExtractorJsonpathHandler {
    id: idSeq,
    ready: false,
  }
  idSeq += 1

  if config.Attributes["application"] == "" {
    log.Println("Error: application not configured")
    return t
  }
  t.application = config.Attributes["application"]
  
  t.deviceSelector = config.Attributes["deviceSelector"]
  if t.deviceSelector[:2] == "J:" {
    jp, err := jsonpath.Compile(t.deviceSelector[2:])
    if err != nil {
      log.Printf("Unable to compile deviceJsonpath: %s, %s", t.deviceSelector[2:], err)
      return t
    }
    t.deviceJsonpath = jp
  }
  t.valueSelector = config.Attributes["valueSelector"]
  if t.valueSelector[:2] == "J:" {
    jp, err := jsonpath.Compile(t.valueSelector[2:])
    if err != nil {
      log.Printf("Unable to compile valueJsonpath: %s, %s", t.valueSelector[2:], err)
      return t
    }
    t.valueJsonpath = jp
  }
  t.unitSelector = config.Attributes["unitSelector"]
  if t.unitSelector[:2] == "J:" {
    jp, err := jsonpath.Compile(t.unitSelector[2:])
    if err != nil {
      log.Printf("Unable to compile unitJsonpath: %s, %s", t.unitSelector[2:], err)
      return t
    }
    t.unitJsonpath = jp
  }

  t.ready = true
  t.dbh = database.NewDatabaseHandle()
  return t
}

func (self *SingleValueExtractorJsonpathHandler) GetId() string {
  return fmt.Sprintf("SVE%d", self.id)
}

func lost(msg string, message handler.MessageT) {
  log.Printf("Error: %s, message %s is lost", msg, message)
}

func extractionHelper(subTopics []string, jPayload interface{}, selector string, jp *jsonpath.Compiled) (string, error) {
  var res string
  switch selector[:2] {
  case "J:":
    r, e := jp.Lookup(jPayload)
    if e != nil {
      return "", fmt.Errorf("jp.Lookup failed with %s", e)
    }
    res = fmt.Sprint(r)
  case "T:":
    i, e := strconv.Atoi(selector[2:])
    if e != nil {
      return "", fmt.Errorf("Atoi failed with %s", e)
    }
    if i >= len(subTopics) {
      return "", fmt.Errorf("not enough subtopics")
    }
    res = subTopics[i]
  case "C:":
    res = selector[2:]
  default:
    return "", fmt.Errorf("Invalid selector: %s", selector[:2])
  }
  return res, nil
}


func (self *SingleValueExtractorJsonpathHandler) Handle(message handler.MessageT) {
  if ! self.ready {
    log.Println("Handler is not marked as ready, message %s is lost", message)
    return
  }
  log.Printf("Handler SingleValueExtractorJsonpath %d processing %s -> %s", self.id, message.Topic, message.Payload)

  var measurement database.Measurement
  measurement.Time = time.Now()
  measurement.Application = self.application
  
  subTopics := strings.Split(message.Topic, "/")
  //log.Printf("Subtopics: %s", strings.Join(subTopics, ", "))
  var jPayload interface{}
  err := json.Unmarshal([]byte(message.Payload), &jPayload)
  if err != nil {
    lost(fmt.Sprintf("Unable to unmarshal payload: %s", err), message)
    return
  }

  device, err1 := extractionHelper(subTopics, jPayload, self.deviceSelector, self.deviceJsonpath)
  if err1 != nil {
    lost(fmt.Sprintf("Device extraction failed with %s", err1), message)
    return
  }
  value, err2 := extractionHelper(subTopics, jPayload, self.valueSelector, self.valueJsonpath)
  if err2 != nil {
    lost(fmt.Sprintf("Value extraction failed with %s", err2), message)
    return
  }
  unit, err3 := extractionHelper(subTopics, jPayload, self.unitSelector, self.unitJsonpath)
  if err3 != nil {
    lost(fmt.Sprintf("Unit extraction failed with %s", err3), message)
    return
  }

  measurement.Device = device

  var variable database.VariableType
  variable.Label = ""
  variable.Variable = ""
  variable.Unit = unit
  variable.Value = value
  measurement.Values = make(map[string]database.VariableType)
  measurement.Values["Value"] = variable

  log.Printf("Prepared measurement item: %s", measurement)
  self.dbh.StoreMeasurement(&measurement)
}