package main

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/simonvetter/modbus"
)

func modbusValuesToFloat(v uint16) float32 {
	return float32(v) / 10.0
}

func (d *daemon) modbusConnect() error {
	var err error

	d.mu.Lock()
	defer d.mu.Unlock()

	// Setup modbus client
	d.modbusClient, err = modbus.NewClient(&modbus.ClientConfiguration{
		URL:     "tcp://10.250.241.20:8887",
		Timeout: 5 * time.Second,
	})
	if err != nil {
		return err
	}
	// Connect to modbus client
	err = d.modbusClient.Open()
	if err != nil {
		return err
	}

	return nil
}

// There are currently two devices connected to the modbus.
// The first one (slave 1) is a temperature/humidity sensor.
// The second one (slave 2) is a PTA8D08 transmitter
func (d *daemon) modbusUpdate() error {
	d.mu.Lock()
	defer d.mu.Unlock()

	var err error
	var registers []uint16 // temperature, humidity

	// Switch to slave 1
	d.modbusClient.SetUnitId(1)

	// Read temperature and humidity
	registers, err = d.modbusClient.ReadRegisters(1, 2, modbus.INPUT_REGISTER)
	if err != nil {
		return err
	}

	if len(registers) != 2 {
		msg := fmt.Sprintf("Expected two registers from modbus slave 1, but got %d", len(registers))
		return errors.New(msg)
	}

	d.daemonState.tempSEM = modbusValuesToFloat(registers[0])
	d.daemonState.humiditySEM = modbusValuesToFloat(registers[1])

	// Switch to slave 2
	d.modbusClient.SetUnitId(2)

	// PT100 mapping
	// Channel 0: Cable -WGA6, Sensor "dp bottom"
	// Channel 1: Cable -WGA8, Sensor "dp inlet"
	// Channel 2: Cable WGA7, Sensor "dp top"
	registers, err = d.modbusClient.ReadRegisters(0, 3, modbus.HOLDING_REGISTER)
	if err != nil {
		return err
	}

	if len(registers) != 3 {
		msg := fmt.Sprintf("Expected three registers from modbus slave 2, but got %d", len(registers))
		return errors.New(msg)
	}

	d.daemonState.tempDPBottom = modbusValuesToFloat(registers[0])
	d.daemonState.tempDPInlet = modbusValuesToFloat(registers[1])
	d.daemonState.tempDPTop = modbusValuesToFloat(registers[2])

	return nil
}

// Call modbusUpdate every second
func (d *daemon) modbusProcess(ctx context.Context) {
	for {
		select {
		case <-ctx.Done():
			return
		default:
			d.modbusUpdate()
			time.Sleep(time.Second * 1)
		}
	}
}