package main

import (
  "bytes"
  "database/sql"
  "fmt"
  "io"
  "io/ioutil"
  "os"
  "path"
  "regexp"
  "strings"
  "text/template"

  _ "github.com/go-sql-driver/mysql"
  "github.com/pin/tftp"
  "github.com/namsral/flag"
)

var (
  workdir, sepTeplateFilePath, freepbxConf string
  sepTeplateFile                           []byte
  db                                       *sql.DB
)

//PhoneSetting struct
type PhoneSetting struct {
  DisplayName, PhonePassword string
  PhoneNumber                string
}

func getDBConnectionParams() (string, error) {
  var con string
  rex := regexp.MustCompile(`\["(.*)"\] = "(.*)";`)
  buf := new(bytes.Buffer)

  file, err := os.Open(freepbxConf)
  if err != nil {
    return con, err
  }
  defer file.Close()

  buf.ReadFrom(file)

  data := rex.FindAllStringSubmatch(buf.String(), -1)

  res := make(map[string]string)
  for _, kv := range data {
    k := kv[1]
    v := kv[2]
    res[k] = v
  }

  con = fmt.Sprintf("%s:%s@tcp(%s)/%s", res["AMPDBUSER"], res["AMPDBPASS"], res["AMPDBHOST"], res["AMPDBNAME"])
  fmt.Fprintf(os.Stderr, "%s:%s@tcp(%s)/%s", res["AMPDBUSER"], res["AMPDBPASS"], res["AMPDBHOST"], res["AMPDBNAME"])
  return con, nil
}

//Getting phone setting from freepbx database
func getPhoneSetting(filename string) (*PhoneSetting, error) {
  var ps PhoneSetting

  filename = strings.TrimSuffix(filename, ".cnf.xml")
  query := `
    SELECT userman_users.displayname, sip.data, userman_users.default_extension
      FROM userman_users
      LEFT JOIN sip
      ON userman_users.default_extension=sip.id AND sip.keyword='secret'
      WHERE userman_users.fax=?
      ORDER BY userman_users.default_extension
    LIMIT 1
    `

  err := db.QueryRow(query, filename).Scan(&ps.DisplayName, &ps.PhonePassword, &ps.PhoneNumber)

  if err != nil {
    return &ps, err
  }

  return &ps, nil
}

//Send file to client
func sendFile(file *bytes.Buffer, rf io.ReaderFrom) error {
  n, err := rf.ReadFrom(file)

  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
    return err
  }
  fmt.Printf("%d bytes sent\n", n)
  return nil
}

//Reading file in tftp dir. If file not found, returning empty file
func readFile(filename string, rf io.ReaderFrom) error {
  var err error

  buf := new(bytes.Buffer)

  file, err := os.Open(path.Join(workdir, filename))
  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
  } else {
    buf.ReadFrom(file)
  }
  defer file.Close()

  err = sendFile(buf, rf)
  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
    return err
  }

  return nil
}

//Generating phone settings file use go-template
func genFile(filename string, rf io.ReaderFrom) error {
  var (
    tpl bytes.Buffer
    err error
  )

  p, err := getPhoneSetting(filename)
  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
    return err
  }

  t := template.Must(template.New("sepTeplateFile").Parse(string(sepTeplateFile)))

  err = t.Execute(&tpl, p)
  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
    return err
  }

  err = sendFile(&tpl, rf)
  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
    return err
  }

  return nil
}

//Processing file request from a tftp client
func readHandler(filename string, rf io.ReaderFrom) error {
  raddr := rf.(tftp.OutgoingTransfer).RemoteAddr()
  laddr := rf.(tftp.RequestPacketInfo).LocalIP()
  fmt.Println("RRQ from:", raddr.String(), "To:", laddr.String(), "File:", filename)

  sepFile, err := path.Match("SEP*.cnf.xml", filename)
  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
    return err
  }

  if sepFile {
    genFile(filename, rf)
  } else {
    readFile(filename, rf)
  }

  return nil
}

//Declaring cli flags
func init() {
  flag.StringVar(&workdir, "workdir", "/tftpboot", "Set working directory")
  flag.StringVar(&sepTeplateFilePath, "sep_template_file", "./sep-cisco.cnf.xml.tpl", "Set path to sep template file")
  flag.StringVar(&freepbxConf, "freepbx_conf", "/etc/freepbx.conf", "Set path to freepbx db connection config file")
}

func main() {
  var err error

  flag.Parse()

  sepTeplateFile, err = ioutil.ReadFile(sepTeplateFilePath)
  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
    os.Exit(1)
  }

  //Getting params for db connection
  dbConnParams, err := getDBConnectionParams()
  if err != nil {
    fmt.Fprintf(os.Stderr, "%v\n", err)
    os.Exit(1)
  }

  //Connicting to db
  db, err = sql.Open("mysql", dbConnParams)
  if err != nil {
    fmt.Fprintf(os.Stderr, "Error on initializing database connection: %s\n", err)
    os.Exit(1)
  }

  //Checking db connection
  err = db.Ping()
  if err != nil {
    fmt.Fprintf(os.Stderr, "Error on database connection: %s\n", err)
    os.Exit(1)
  }

  db.SetMaxIdleConns(10)

  fmt.Println("Starting freepbx tftp server")

  s := tftp.NewServer(readHandler, nil)
  err = s.ListenAndServe(":69")
  if err != nil {
    fmt.Fprintf(os.Stderr, "server: %v\n", err)
    os.Exit(1)
  }
}