package main

import (
	"log"
	"strconv"
	"time"

	"github.com/simonvetter/modbus"
)

var (
	tcp_server *modbus.ModbusServer
	rtu_client *modbus.ModbusClient
	Logger     log.Logger = *log.Default()
)

const (
	SERVER           = "[::]"
	PORT             = 502
	SERIAL_INTERFACE = "/dev/ttyUSB0"
	BAUD             = 9600
)

func init() {
	Logger.SetPrefix("modbus_bridge: ")
	Logger.Println("Starting")

	// create modbus tcp server
	timeout := 30 * time.Second
	var server_cfg = modbus.ServerConfiguration{
		URL:        "tcp://" + SERVER + ":" + strconv.Itoa(PORT),
		Timeout:    timeout,
		MaxClients: 5,
	}
	var err error
	handler := &modbusTcpHandler{}
	tcp_server, err = modbus.NewServer(&server_cfg, handler)
	if err != nil {
		Logger.Printf("failed to create server: %v\n", err)
		return
	}

	// create modbus rtu client
	url := "rtu://" + SERIAL_INTERFACE
	rtu_client, err = modbus.NewClient(&modbus.ClientConfiguration{
		URL:      url,
		Speed:    BAUD,
		DataBits: 8,
		Parity:   modbus.PARITY_NONE,
		StopBits: 1,
		Timeout:  300 * time.Millisecond,
	})
	if err != nil {
		Logger.Printf("Could not create new modbus rtu client on %s (%s).", url, err.Error())
		err = modbus.ErrConfigurationError
		return
	}
	err = rtu_client.Open()
	if err != nil {
		Logger.Printf("Could not open new modbus rtu client on %s (%s).", url, err.Error())
		err = modbus.ErrConfigurationError
		return
	}
}

func main() {
	if tcp_server != nil {
		Logger.Print("Starting modbus tcp server")
		err := tcp_server.Start()
		if err != nil {
			Logger.Printf("Unable to start modbus tcp server: %s", err.Error())
		}
	}
	for {
		time.Sleep(time.Millisecond * 500)
	}
}