package modbusx

import (
	"encoding/binary"
)

func Read(ipAddr string, address uint16, quantity uint16) (data []byte, err error) {
	address--
	cli := getModbusConnection(ipAddr)
	data, err = cli.ReadHoldingRegisters(address, quantity)
	dealErr(err, ipAddr)
	if err != nil {
		cli = getModbusConnection(ipAddr)
		data, err = cli.ReadHoldingRegisters(address, quantity)
		dealErr(err, ipAddr)
	}
	return
}

func Write(ipAddr string, address uint16, value int) (err error) {
	address--
	var bytesVal []byte
	bytesVal = intToBytes(value)
	cli := getModbusConnection(ipAddr)
	_, err = cli.WriteMultipleRegisters(address, uint16(len(bytesVal)), bytesVal)
	dealErr(err, ipAddr)
	return err
}

func intToBytes(value int) (data []byte) {
	if value <= 1<<16 {
		data = make([]byte, 2)
		binary.BigEndian.PutUint16(data, uint16(value))
	} else {
		data = make([]byte, 4)
		binary.BigEndian.PutUint32(data, uint32(value))
	}
	return
}

func dealErr(err error, ipAddr string) {
	if err != nil {
		unsetModbusConnection(ipAddr) //失败则删除缓存的连接
	}
}