package webutility

  
  import (

  	"database/sql"

  	"encoding/json"

  	"errors"

  	"fmt"

  	"io"

  	"net/http"

  	"strings"

  	"sync"

  	"time"

  )

  var (

  	mu       = &sync.Mutex{}
  	metadata = make(map[string]Payload)

  	updateQue = make(map[string][]byte)

  	metadataDB    *sql.DB

  	activeProject string

  	inited     bool
  	metaDriver string

  )

  // LangMap ...

  type LangMap map[string]map[string]string

  // Field ...

  type Field struct {

  	Parameter string `json:"param"`
  	Type      string `json:"type"`
  	Visible   bool   `json:"visible"`
  	Editable  bool   `json:"editable"`

  }

  // CorrelationField ...

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

  // Translation ...

  type Translation struct {

  	Language     string            `json:"language"`

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

  }

  // PaginationLinks ...

  type PaginationLinks struct {
  	Base string `json:"base"`
  	Next string `json:"next"`
  	Prev string `json:"prev"`
  	Self string `json:"self"`
  }

  // PaginationParameters ...

  type PaginationParameters struct {

  	URL    string `json:"-"`

  	Offset int64  `json:"offset"`
  	Limit  int64  `json:"limit"`
  	SortBy string `json:"sortBy"`
  	Order  string `json:"order"`
  }

  // GetPaginationParameters ...

  // TODO(marko)
  func GetPaginationParameters(req *http.Request) (p PaginationParameters) {
  	return p
  }
  
  // TODO(marko)
  func (p *PaginationParameters) paginationLinks() (links PaginationLinks) {
  	return links
  }

  // Payload ...

  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"`

  	// Pagination

  	Count int64           `json:"count"`
  	Total int64           `json:"total"`
  	Links PaginationLinks `json:"_links"`

  
  	// Data holds JSON payload. It can't be used for itteration.

  	Data interface{} `json:"data"`

  }

  func (p *Payload) addLang(code string, labels map[string]string) {
  	t := Translation{
  		Language:     code,
  		FieldsLabels: labels,
  	}
  	p.Lang = append(p.Lang, t)
  }

  // SetData ...

  func (p *Payload) SetData(data interface{}) {
  	p.Data = data
  }

  // SetPaginationInfo ...

  func (p *Payload) SetPaginationInfo(count, total int64, params PaginationParameters) {

  	p.Count = count
  	p.Total = total

  	p.Links = params.paginationLinks()

  }

  // NewPayload returs a payload sceleton for entity described with key.
  func NewPayload(r *http.Request, key string) Payload {
  	p := metadata[key]
  	p.Method = r.Method + " " + r.RequestURI
  	return p

  }
  
  // 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)
  }

  // InitPayloadsMetadata loads all payloads' information into 'metadata' variable.
  func InitPayloadsMetadata(drv string, db *sql.DB, project string) error {

  	var err error

  	if drv != "ora" && drv != "mysql" {

  		err = errors.New("driver not supported")
  		return err

  	}

  	metaDriver = drv

  	metadataDB = db
  	activeProject = project

  	mu.Lock()
  	defer mu.Unlock()

  	err = initMetadata(project)

  	if err != nil {
  		return err
  	}

  	inited = true
  
  	return nil
  }

  // EnableHotloading ...

  func EnableHotloading(interval int) {
  	if interval > 0 {
  		go hotload(interval)
  	}
  }

  // GetMetadataForAllEntities ...

  func GetMetadataForAllEntities() map[string]Payload {
  	return metadata
  }

  // GetMetadataForEntity ...

  func GetMetadataForEntity(t string) (Payload, bool) {
  	p, ok := metadata[t]
  	return p, ok
  }

  // QueEntityModelUpdate ...

  func QueEntityModelUpdate(entityType string, v interface{}) {
  	updateQue[entityType], _ = json.Marshal(v)
  }

  // UpdateEntityModels ...

  func UpdateEntityModels(command string) (total, upd, add int, err error) {
  	if command != "force" && command != "missing" {
  		return total, 0, 0, errors.New("webutility: unknown command: " + command)
  	}
  
  	if !inited {

  		return 0, 0, 0, errors.New("webutility: metadata not initialized but update was tried")

  	}
  
  	total = len(updateQue)
  
  	toUpdate := make([]string, 0)
  	toAdd := make([]string, 0)

  	for k := range updateQue {

  		if _, exists := metadata[k]; exists {
  			if command == "force" {
  				toUpdate = append(toUpdate, k)
  			}
  		} else {
  			toAdd = append(toAdd, k)
  		}
  	}
  
  	var uStmt *sql.Stmt

  	if metaDriver == "ora" {

  		uStmt, err = metadataDB.Prepare("update entities set entity_model = :1 where entity_type = :2")
  		if err != nil {
  			return
  		}

  	} else if metaDriver == "mysql" {

  		uStmt, err = metadataDB.Prepare("update entities set entity_model = ? where entity_type = ?")
  		if err != nil {
  			return
  		}
  	}
  	for _, k := range toUpdate {

  		_, err = uStmt.Exec(string(updateQue[k]), k)
  		if err != nil {

  			return
  		}
  		upd++
  	}
  
  	blankPayload, _ := json.Marshal(Payload{})
  	var iStmt *sql.Stmt

  	if metaDriver == "ora" {

  		iStmt, err = metadataDB.Prepare("insert into entities(projekat, metadata, entity_type, entity_model) values(:1, :2, :3, :4)")
  		if err != nil {
  			return
  		}

  	} else if metaDriver == "mysql" {

  		iStmt, err = metadataDB.Prepare("insert into entities(projekat, metadata, entity_type, entity_model) values(?, ?, ?, ?)")
  		if err != nil {
  			return
  		}
  	}
  	for _, k := range toAdd {
  		_, err = iStmt.Exec(activeProject, string(blankPayload), k, string(updateQue[k]))
  		if err != nil {

  			return
  		}
  		metadata[k] = Payload{}
  		add++
  	}
  
  	return total, upd, add, nil
  }

  func initMetadata(project string) error {
  	rows, err := metadataDB.Query(`select
  		entity_type,
  		metadata
  		from entities
  		where projekat = ` + fmt.Sprintf("'%s'", project))
  	if err != nil {
  		return err
  	}
  	defer rows.Close()

  	if len(metadata) > 0 {
  		metadata = nil
  	}
  	metadata = make(map[string]Payload)
  	for rows.Next() {
  		var name, load string
  		rows.Scan(&name, &load)
  
  		p := Payload{}
  		err := json.Unmarshal([]byte(load), &p)
  		if err != nil {

  			fmt.Printf("webutility: couldn't init: '%s' metadata: %s:
  %s
  ", name, err.Error(), load)

  		} else {

  			metadata[name] = p
  		}

  	}

  
  	return nil
  }

  // LoadMetadataFromFile expects file in format:

  //
  // [ payload A identifier ]

  // key1 = value1
  // key2 = value2

  // ...
  // [ payload B identifier ]

  // key1 = value1
  // key2 = value2

  // ...

  //
  // TODO(marko): Currently supports only one hardcoded language...

  func LoadMetadataFromFile(path string) error {

  	lines, err := ReadFileLines(path)

  	if err != nil {
  		return err
  	}

  	metadata = make(map[string]Payload)
  
  	var name string

  	for i, l := range lines {

  		// skip empty lines

  		if l = strings.TrimSpace(l); len(l) == 0 {

  			continue
  		}

  		if IsWrappedWith(l, "[", "]") {

  			name = strings.Trim(l, "[]")

  			p := Payload{}
  			p.addLang("sr", make(map[string]string))
  			metadata[name] = p

  			continue
  		}

  		if name == "" {

  			return fmt.Errorf("webutility: LoadMetadataFromFile: error on line %d: [no header] [%s]", i+1, l)

  		}

  		parts := strings.Split(l, "=")

  		if len(parts) != 2 {

  			return fmt.Errorf("webutility: LoadMetadataFromFile: error on line %d: [invalid format] [%s]", i+1, l)

  		}

  		k := strings.TrimSpace(parts[0])
  		v := strings.TrimSpace(parts[1])

  		if v != "-" {
  			metadata[name].Lang[0].FieldsLabels[k] = v

  		}
  	}
  
  	return nil
  }

  func hotload(n int) {
  	entityScan := make(map[string]int64)
  	firstCheck := true
  	for {
  		time.Sleep(time.Duration(n) * time.Second)
  		rows, err := metadataDB.Query(`select
  			ora_rowscn,
  			entity_type
  			from entities where projekat = ` + fmt.Sprintf("'%s'", activeProject))
  		if err != nil {

  			fmt.Printf("webutility: hotload failed: %v
  ", err)

  			time.Sleep(time.Duration(n) * time.Second)
  			continue
  		}
  
  		var toRefresh []string
  		for rows.Next() {
  			var scanID int64
  			var entity string
  			rows.Scan(&scanID, &entity)
  			oldID, ok := entityScan[entity]
  			if !ok || oldID != scanID {
  				entityScan[entity] = scanID
  				toRefresh = append(toRefresh, entity)
  			}
  		}
  		rows.Close()
  
  		if rows.Err() != nil {

  			fmt.Printf("webutility: hotload rset error: %v
  ", rows.Err())

  			time.Sleep(time.Duration(n) * time.Second)
  			continue
  		}
  
  		if len(toRefresh) > 0 && !firstCheck {
  			mu.Lock()
  			refreshMetadata(toRefresh)
  			mu.Unlock()
  		}
  		if firstCheck {
  			firstCheck = false
  		}
  	}
  }
  
  func refreshMetadata(entities []string) {
  	for _, e := range entities {
  		fmt.Printf("refreshing %s
  ", e)
  		rows, err := metadataDB.Query(`select
  			metadata
  			from entities
  			where projekat = ` + fmt.Sprintf("'%s'", activeProject) +
  			` and entity_type = ` + fmt.Sprintf("'%s'", e))
  
  		if err != nil {

  			fmt.Printf("webutility: refresh: prep: %v
  ", err)

  			rows.Close()
  			continue
  		}
  
  		for rows.Next() {
  			var load string
  			rows.Scan(&load)
  			p := Payload{}
  			err := json.Unmarshal([]byte(load), &p)
  			if err != nil {

  				fmt.Printf("webutility: couldn't refresh: '%s' metadata: %s
  %s
  ", e, err.Error(), load)

  			} else {
  				metadata[e] = p
  			}
  		}
  		rows.Close()
  	}
  }

  /*

  func ModifyMetadataForEntity(entityType string, p *Payload) error {
  	md, err := json.Marshal(*p)

  	if err != nil {
  		return err
  	}

  	mu.Lock()
  	defer mu.Unlock()

  	_, err = metadataDB.PrepAndExe(`update entities set
  		metadata = :1
  		where projekat = :2
  		and entity_type = :3`,
  		string(md),
  		activeProject,
  		entityType)
  	if err != nil {
  		return err

  	}
  	return nil
  }

  func DeleteEntityModel(entityType string) error {
  	_, err := metadataDB.PrepAndExe("delete from entities where entity_type = :1", entityType)
  	if err == nil {
  		mu.Lock()
  		delete(metadata, entityType)
  		mu.Unlock()
  	}
  	return err

  }

  */