package main

import (
	"context"
	"encoding/json"
	"flag"
	"log"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/simonvetter/modbus"

	influxdb2 "github.com/influxdata/influxdb-client-go/v2"
)

type mod_bus struct {
	Protocol     string `json:"protocol"`
	BaudRate     int    `json:"baud_rate"`
	SlaveAddress int    `json:"slave_address"`
	Host         string `json:"host"`
	Port         int    `json:"port"`
}

type register struct {
	Name     string  `json:"name"`
	Type     string  `json:"type"`
	Address  int     `json:"address"`
	Quantity int     `json:"quantity"`
	Factor   float32 `json:"factor"`
	Unit     string  `json:"unit"`
}

type device struct {
	Name      string     `json:"name"`
	Type      string     `json:"type"`
	Modbus    mod_bus    `json:"modbus"`
	Registers []register `json:"registers"`
}
type config struct {
	SampleRate    int      `json:"sample_rate"`
	InfluxdbHost  string   `json:"influxdb_host"`
	InfluxdbPort  int      `json:"influxdb_port"`
	InfluxdbToken string   `json:"influxdb_token"`
	Devices       []device `json:"devices"`
}

var (
	logger       log.Logger = *log.Default()
	config_path  string
	config_cache config
)

func init() {
	logger.SetFlags(log.Llongfile | log.Ltime)
}

func read_config() {
	data, err := os.ReadFile(config_path)
	if err != nil {
		logger.Printf("Unable to read %s", config_path)
		return
	}
	err = json.Unmarshal(data, &config_cache)
	if err != nil {
		logger.Print("Unable to evaluate config data")
		return
	}
}

func main() {
	flag.StringVar(&config_path, "c", "../config/config.json", "Specify path to find the config file. Default is ../config/config.json")
	flag.Parse()
	read_config()

	type remote struct {
		client    *modbus.ModbusClient
		registers []register
		name      string
	}
	var err error
	var remotes []remote
	var client *modbus.ModbusClient

	// setup influx connection
	influxdb_url := "http://" + config_cache.InfluxdbHost + ":" + strconv.Itoa(config_cache.InfluxdbPort)
	db_client := influxdb2.NewClient(influxdb_url, config_cache.InfluxdbToken)
	defer db_client.Close()
	ctx := context.Background()
	write_api := db_client.WriteAPIBlocking("tkl", "home")

	for _, v := range config_cache.Devices {
		if v.Modbus.Protocol == "tcp" {
			url := v.Modbus.Protocol + "://" + v.Modbus.Host + ":" + strconv.Itoa(v.Modbus.Port)
			client, err = modbus.NewClient(&modbus.ClientConfiguration{URL: url})
			if err != nil {
				logger.Printf("failed to create modbus client: %v\n", err)
				continue
			}
			client.SetUnitId(0x55)
			err = client.Open()
			if err != nil {
				logger.Printf("failed to connect: %v\n", err)
				continue
			}

			var tmp remote
			tmp.client = client
			tmp.registers = v.Registers
			tmp.name = v.Name
			remotes = append(remotes, tmp)
		}
	}

	for { // ever
		for _, remote := range remotes {
			point := influxdb2.NewPointWithMeasurement(remote.name)
			for _, reg := range remote.registers {
				res, err := remote.client.ReadRegisters(uint16(reg.Address), uint16(reg.Quantity), modbus.HOLDING_REGISTER)
				if err != nil {
					logger.Printf("failed to read: %v\n", err)
					error_strings := []string{
						"connection reset by peer",
						"broken pipe",
					}
					for _, error_string := range error_strings {
						if strings.Contains(err.Error(), error_string) {
							logger.Print("trying to restart modbus client")
							remote.client.Close()
							err = remote.client.Open()
							if err != nil {
								logger.Printf("failed to restart: %v\n", err)
								os.Exit(1)
							}
						}
					}
					continue
				}
				var tmp int32
				switch reg.Quantity {
				case 1:
					tmp = int32(res[0])
				case 2:
					tmp = ((int32(res[0]) << 16) | int32(res[1]))
				default:
					logger.Printf("Unsupported quantity of registers (%d)", reg.Quantity)
					continue
				}
				result := float32(tmp) * reg.Factor
				point.AddField(reg.Name, result)
			}
			point.SetTime(time.Now())
			err := write_api.WritePoint(ctx, point)
			if err != nil {
				logger.Print(err)
			}
			err = write_api.Flush(ctx)
			if err != nil {
				logger.Print(err)
			}
		}
		time.Sleep(time.Duration(config_cache.SampleRate * 1000000000))
	}
}