package databaseutils

import (
  "database/sql"
  _ "github.com/go-sql-driver/mysql"
  "errors"
)

var (
  DBUtil *DBUtils // DB handle for global access
)

const ( // Error constants
  ERR_EMPTY_RESULT = "ERR_EMPTY_RESULT"
  ERR_NO_COLUMNS = "ERR_NO_COLUMNS"
  ERR_FAILED_ROW_SCAN = "ERR_FAILED_ROW_SCAN"
)

type DBUtils struct {
  User string
  Password string
  Host string
  Database string
  Handle *sql.DB
}

func (dbUtil *DBUtils) Connect() { // setup handle for db
  var err error
  dbUtil.Handle, err = sql.Open("mysql", dbUtil.User + ":" + dbUtil.Password + "@tcp(" + dbUtil.Host + ")/" + dbUtil.Database) // open handle
  if err != nil {
    panic(err.Error()) // TODO
  }

  err = dbUtil.Handle.Ping() // try to connect
  if err != nil {
    panic(err.Error()) // TODO
  }
}

func (dbUtil DBUtils) Close() {
  dbUtil.Handle.Close()
}

func (dbUtil DBUtils) GetString(what string, from string, where string, wherevalue string) string {
  var buf string

  rows, err := dbUtil.Handle.Query("SELECT " + what + " FROM " + from + " WHERE " + where + " = " + wherevalue) // TODO Parse?
  if err != nil {
  	panic(err.Error()) // TODO
  }
  defer rows.Close()

  for rows.Next() {
  	err := rows.Scan(&buf)
  	if err != nil {
  		panic(err.Error()) // TODO
  	}
  }

  err = rows.Err()
  if err != nil {
  	panic(err.Error()) // TODO
  }

  return buf
}

// GetRow(what, from, where, wherevalue)
func (dbUtil DBUtils) GetRow(options ...string) ([]string, error) {
  var err error
  var rows *sql.Rows // TODO fix this weird bug

  if len(options) > 3 { // with or without where
    rows, err = dbUtil.Handle.Query("SELECT " + options[0] + " FROM " + options[1] + " WHERE " + options[2] + " = \"" + options[3] + "\"") // TODO Parse?
  } else {
    rows, err = dbUtil.Handle.Query("SELECT " + options[0] + " FROM " + options[1]) // TODO Parse?
  }
  defer rows.Close()

  if err != nil {
    panic(err.Error()) // TODO
  }

  cols, err := rows.Columns()
   if err != nil {
     return []string{""}, errors.New(ERR_NO_COLUMNS)
   }

   dest := make([]interface{}, len(cols)) // interface for scanning
   result := make([]sql.NullString, len(cols)) // NullString to check if empty
   results := make([]string, len(cols)) // final return-result

   for i, _ := range result {
     dest[i] = &result[i] // Put pointers to each string in the interface slice
   }

  for rows.Next() {
    err = rows.Scan(dest...) // copy results in dest
    if err != nil {
        return []string{""}, errors.New(ERR_FAILED_ROW_SCAN)
    }
  }

  errcounter := 0 // count invalid results

  for i, _ := range result {
    if result[i].Valid {
      results[i] = result[i].String // store valid results in return-slice
    } else {
      errcounter++
    }
  }

  if errcounter == len(cols) { // if nothings valid it's empty
    return []string{""}, errors.New(ERR_EMPTY_RESULT)
  }

  return results, nil
}

//TODO GetRows