package webutility

  
  import (
  	"net/http"

  	"encoding/json"
  	"errors"
  	"gopkg.in/rana/ora.v3"
  	"io"
  	"io/ioutil"

  	"sync"

  )

  var mu = &sync.Mutex{}

  var payloads []payloadBuff

  type LangMap map[string]map[string]string
  
  type Field struct {
  	Parameter  string `json:"param"`
  	Type       string `json:"type"`
  	Visible    bool   `json:"visible"`
  	Editable   bool   `json:"editable"`
  }

  type CorrelationField struct {
  	Result   string   `json:"result"`
  	Elements []string `json:"elements"`
  	Type     string   `json:"type"`
  }
  
  type Translation struct {

  	Language     string            `json:"language"`

  	FieldsLabels map[string]string `json:"fieldsLabels"`

  }

  type payloadBuff struct {

  	Type         string             `json:"tableType"`

  	Method	     string             `json:"method"`
  	Params	     map[string]string  `json:"params"`

  	Lang	     []Translation      `json:"lang"`

  	Fields	     []Field            `json:"fields"`

  	Correlations []CorrelationField `json:"correlationFields"`

  	IdField      string             `json:"idField"`

  	// Data can only hold slices of any type. It can't be used for itteration
  	Data	     interface{}        `json:"data"`
  }

  type Payload struct {
  	Method	     string             `json:"method"`
  	Params	     map[string]string  `json:"params"`
  	Lang	     []Translation      `json:"lang"`
  	Fields	     []Field            `json:"fields"`
  	Correlations []CorrelationField `json:"correlationFields"`
  	IdField      string             `json:"idField"`

  	// Data can only hold slices of any type. It can't be used for itteration
  	Data	     interface{}        `json:"data"`
  }

  // NewPayload returs a payload sceleton for provided table.

  func NewPayload(r *http.Request, table string) Payload {
  	var pload Payload

  	pload.Method = r.Method + " " + r.URL.Path

  	if table != "" {
  		pload.Params = make(map[string]string, 0)

  		pload.Lang = translations(table)
  		pload.Fields = fields(table)
  		pload.IdField = id(table)
  		pload.Correlations = correlations(table)

  	}

  	return pload
  }

  // DeliverPayload encodes payload to w.

  func DeliverPayload(w http.ResponseWriter, payload Payload) {
  	json.NewEncoder(w).Encode(payload)
  	payload.Data = nil

  }

  // translations returns a slice of translations for a payload/table of ptype type.
  func translations(ptype string) []Translation {
  	var translations []Translation

  	for _, pload := range payloads {
  		if pload.Type == ptype {

  			for _, t := range pload.Lang {

  				translations = append(translations, Translation{
  					Language: t.Language,
  					FieldsLabels: t.FieldsLabels,
  				})
  			}
  		}

  	}

  
  	return translations
  }

  // fields returns a slice of fields for a payload/table of ptype type.
  func fields(ptype string) []Field {
  	var fields []Field

  	for _, pload := range payloads {
  		if pload.Type == ptype {

  			for _, f := range pload.Fields {
  				fields = append(fields, f)
  			}
  		}
  	}
  
  	return fields
  }

  // id returns the name of ID field of a payload/table of ptype type.
  func id(ptype string) string {
  	for _, pload := range payloads {
  		if pload.Type == ptype {

  			return pload.IdField
  		}
  	}
  	return ""
  }

  // correlations returns a slice of correlation fields for a payload/table of ptype type.
  func correlations(ptype string) []CorrelationField {
  	var corr []CorrelationField

  	for _, pload := range payloads {
  		if pload.Type == ptype {
  			for _, c := range pload.Correlations {
  				corr = append(corr, c)

  			}
  		}
  	}

  	return corr

  }

  // InitTables loads all payloads in the payloads variable.
  // Returns an error if it fails.

  func InitTables(db *ora.Ses, project string) error {

  	jsonbuf, _ := fetchJSON(db, EqualQuotes(project))

  	mu.Lock()
  	defer mu.Unlock()

  	json.Unmarshal(jsonbuf, &payloads)
  	if len(payloads) == 0 {

  		return errors.New("tables config is corrupt")
  	}

  	return nil
  }

  // fetchJSON returns a byte slice of JSON configuration file from TABLES_CONFIG table.
  // Returns an error if it fails.

  func fetchJSON(db *ora.Ses, project string) ([]byte, error) {

  	stmt, err := db.Prep(`SELECT
  		JSON_CLOB
  		FROM TABLES_CONFIG
  		WHERE PROJEKAT` + project, ora.S)
  	defer stmt.Close()
  
  	if err != nil {
  		return nil, err
  	}
  
  	rset, err := stmt.Qry()
  	if err != nil {
  		return nil, err
  	}
  
  	bytes := make([]byte, 0)
  	if rset.Next() {
  		lob := rset.Row[0].(io.Reader)
  		bytes, err = ioutil.ReadAll(lob)
  		if err != nil {

  			// Ignore for now, it's some weird streaming read/write LOB error.

  			// TODO: Find a fix for this.

  			//return nil, err

  		}

  	}

  	return bytes, nil

  }

  // DecodeJSON decodes JSON data from r to v.
  // Returns an error if it fails.

  func DecodeJSON(r io.Reader, v interface{}) error {
  	return json.NewDecoder(r).Decode(v)
  }