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 {
	var err error

	// Switch to slave 1 (BTA1)
	d.modbusClient.SetUnitId(1)

	// Read temperature and humidity
	var registersBTA1 []uint16 // temperature, humidity
	registersBTA1, err = d.modbusClient.ReadRegisters(1, 2, modbus.INPUT_REGISTER)
	if err != nil {
		return err
	}

	if len(registersBTA1) != 2 {
		msg := fmt.Sprintf("Expected two registers from modbus slave 1, but got %d", len(registersBTA1))
		return errors.New(msg)
	}

	d.mu.Lock()
	d.daemonState.tempSEM = modbusValuesToFloat(registersBTA1[0])
	d.daemonState.humiditySEM = modbusValuesToFloat(registersBTA1[1])
	d.mu.Unlock()

	// Switch to slave 2 (KEC2)
	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"
	var registersKEC2 []uint16 // temperatures dp
	registersKEC2, err = d.modbusClient.ReadRegisters(0, 3, modbus.HOLDING_REGISTER)
	if err != nil {
		return err
	}

	if len(registersKEC2) != 3 {
		return fmt.Errorf("expected three registers from modbus slave 2, but got %d", len(registersKEC2))
	}

	d.mu.Lock()
	d.daemonState.tempDPBottom = modbusValuesToFloat(registersKEC2[0])
	d.daemonState.tempDPInlet = modbusValuesToFloat(registersKEC2[1])
	d.daemonState.tempDPTop = modbusValuesToFloat(registersKEC2[2])
	d.mu.Unlock()

	// Switch to slave 3 (KEC1)
	d.modbusClient.SetUnitId(3)

	// Do a read first to avoid side-effects from the subsequent write to the relay states
	var digitalInputs [8]bool
	var digitalInputRegisters []uint16

	digitalInputRegisters, err = d.modbusClient.ReadRegisters(0x81, 8, modbus.HOLDING_REGISTER)
	if err != nil {
		return err
	}
	// Convert MODBUS words into bools
	for idx, value := range digitalInputRegisters {
		if value != 0 {
			digitalInputs[idx] = true
		} else {
			digitalInputs[idx] = false
		}
	}
	// TODO: Input mapping goes here

	// KFA1-KFA8
	var relayState [8]bool
	d.mu.Lock()
	// -KFA1 Roughing Pump (normally closed contact)
	relayState[0] = !d.daemonState.rpOn
	// -KFA2 Diffusion Pump
	relayState[1] = d.daemonState.dpOn
	// -KFA4 Button Vent
	relayState[3] = d.daemonState.vent.output
	// -KFA5 Button Pump-Down
	relayState[4] = d.daemonState.pumpdown.output
	// -KFA6 Fake-Pirani Rough (normally closed contact)
	relayState[5] = !d.aboveRough.output
	// -KFA7 Fake-Pirani High (normally closed contact)
	relayState[6] = !d.aboveHigh.output
	d.mu.Unlock()

	// The KEC1 module uses a non-standard MODBUS interface
	// instead of coils
	// 0x0100 is the open command
	// 0x0200 is the close command
	// We write 8 words (16-bit) to address 0x01 to update the relays
	var registerValuesKEC1 [8]uint16
	// Convert the boolean values to the commands
	for idx, state := range relayState {
		if state {
			registerValuesKEC1[idx] = 0x0100
		} else {
			registerValuesKEC1[idx] = 0x0200
		}
	}

	err = d.modbusClient.WriteRegisters(0x01, registerValuesKEC1[:])
	if err != nil {
		return err
	}

	return nil
}

// Call modbusUpdate every 100 milliseconds
func (d *daemon) modbusProcess(ctx context.Context) {
	for {
		select {
		case <-ctx.Done():
			return
		default:
			d.modbusUpdate()
			time.Sleep(time.Millisecond * 100)
		}
	}
}