package main

import (
	"bytes"
	"context"
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"os/signal"
	"strconv"
	"syscall"
	"time"
	"unicode"

	"github.com/influxdata/influxdb-client-go/v2"
	"github.com/influxdata/influxdb-client-go/v2/api/write"
	"github.com/tarm/serial"
)

var myZone = ""

func readSerial(s *serial.Port, c chan []byte) {
	var unread bytes.Buffer
	buf := make([]byte, 128)

	for {
		n, err := s.Read(buf)
		if err != nil {
			log.Fatal(err)
		}

		unread.Write(buf[:n])

		for {
			line, err := unread.ReadBytes(2)
			if err == io.EOF {
				if _, err = unread.Write(line); err != nil {
					log.Println(err)
				}
				break
			} else if err != nil {
				log.Println(err)
				break
			}

			c <- bytes.TrimRightFunc(line, unicode.IsControl)
		}
	}
}

func defaultTags() map[string]string {
	ret := map[string]string{}

	if myZone != "" {
		ret["zone"] = myZone
	}

	if host, err := os.Hostname(); err == nil {
		ret["host"] = host
	}

	return ret
}

func fillUnit(tags *map[string]string, key string) {
	if v, ok := MeasurementUnits[key]; ok {
		(*tags)["unit"] = v
	}
}

func getValue(key string, data []byte) interface{} {
	if _, ok := MeasurementUnits[key]; ok {
		ret, _ := strconv.Atoi(string(data))
		return ret
	} else {
		return string(data)
	}
}

func genMeasurements(m map[string][]byte, horodate time.Time) (points []*write.Point) {
	measurmentdone := []string{}

	// Treat MeasurementGroups
	for kgrp, grp := range MeasurementGroups {
		fields := map[string]interface{}{}

		for _, k := range grp {
			measurmentdone = append(measurmentdone, k)

			if v, ok := m[k]; ok {
				fields[k] = getValue(k, v)
			}
		}

		if len(fields) == 0 {
			continue
		}

		tags := defaultTags()
		fillUnit(&tags, grp[0])

		points = append(points, influxdb2.NewPoint(kgrp,
			tags,
			fields,
			horodate,
		))
	}

	// Treat int
munits:
	for k := range MeasurementUnits {
		if _, ok := m[k]; !ok {
			continue
		}

		for _, mg := range measurmentdone {
			if mg == k {
				continue munits
			}
		}

		tags := defaultTags()
		fillUnit(&tags, k)

		points = append(points, influxdb2.NewPoint(k,
			tags,
			map[string]interface{}{"value": getValue(k, m[k])},
			horodate,
		))
	}

	// Treat string
	for _, k := range MeasurementStrings {
		if _, ok := m[k]; !ok {
			continue
		}

		tags := defaultTags()
		fillUnit(&tags, k)

		points = append(points, influxdb2.NewPoint(k,
			tags,
			map[string]interface{}{"value": getValue(k, m[k])},
			horodate,
		))
	}

	return
}

func treatFrames(frames chan []byte, client influxdb2.Client) {
	first := true
	writeAPI := client.WriteAPIBlocking("", "teleinfo/autogen")
fframe:
	for {
		frame := <-frames

		// Skip the first frame because it's not complete
		if first {
			first = false
			continue
		}

		points := []*write.Point{}

		var defaultHorodate time.Time

		m := map[string][]byte{}

		for _, line := range bytes.Split(frame, []byte("\r\n")) {
			key, horodate, data, err := treatLine(line)

			if err != nil {
				log.Println(err)
				continue
			}

			// Skip ADCO, this is the Linky address, confidential and unrelevant
			if key == "ADCO" {
				continue
			}

			if key == "DATE" {
				if horodate == nil {
					continue fframe
				}
				defaultHorodate = *horodate
				continue
			}

			if horodate == nil {
				m[key] = data
			} else {
				tags := defaultTags()
				fillUnit(&tags, key)

				points = append(points, influxdb2.NewPoint(key,
					tags,
					map[string]interface{}{"value": getValue(key, data)},
					*horodate,
				))
			}
		}

		points = append(points, genMeasurements(m, defaultHorodate)...)

		err := writeAPI.WritePoint(context.Background(), points...)
		if err != nil {
			log.Println("Unable to write points:", err)
		}
	}
}

func computeChecksum(area []byte) (checksum byte) {
	for _, c := range area {
		checksum += c
	}

	checksum = (checksum & 0x3F) + 0x20

	return
}

func getHorodate(fields *[][]byte) (*time.Time, error) {
	if (len(*fields) == 4 || string((*fields)[0]) == "DATE") && len((*fields)[1]) == 13 {
		horodate, err := time.Parse("060102150405", string((*fields)[1][1:]))
		if err != nil {
			return nil, err
		}

		// Handle "saison"
		if (*fields)[1][0] == 'E' || (*fields)[1][0] == 'e' {
			horodate = horodate.Add(-2 * time.Hour)
		} else {
			horodate = horodate.Add(-1 * time.Hour)
		}

		// Mark field as treated
		*fields = append((*fields)[:1], (*fields)[2:]...)

		return &horodate, nil
	}

	return nil, nil
}

func treatLine(line []byte) (key string, horodate *time.Time, data []byte, err error) {
	line = bytes.TrimSpace(line)

	if len(line) <= 1 {
		return
	}

	if computeChecksum(line[:len(line)-1]) != line[len(line)-1] {
		log.Printf("BAD checksum on %s: calculated: %c\n", line, computeChecksum(line[:len(line)-1]))
		return
	}

	fields := bytes.Fields(line)

	key = string(fields[0])

	horodate, err = getHorodate(&fields)
	if err != nil {
		return
	}

	data = bytes.Join(fields[1:len(fields)-1], []byte{' '})

	return
}

func main() {
	var influxScheme = flag.String("influx-scheme", "http", "Scheme to use to contact InfluxDB")
	var influxHost = flag.String("influx-host", "localhost", "Host where lives InfluxDB")
	var influxPort = flag.Uint("influx-port", 8086, "Port where InfluxDB is accessible")
	var influxUser = flag.String("influx-username", "influx", "Username to use to perform authentication")
	var influxPass = flag.String("influx-password", "", "Password to use to perform authentication")
	flag.StringVar(&myZone, "tag-zone", myZone, "Tag zone to add to points")
	flag.Parse()

	if len(flag.Args()) < 1 {
		log.Println("missing required argument: serial device (eg. /dev/ttyUSB0)")
		return
	}

	config := &serial.Config{
		Name:     flag.Args()[0],
		Baud:     9600,
		Size:     7,
		Parity:   serial.ParityNone,
		StopBits: 1,
	}

	s, err := serial.OpenPort(config)
	if err != nil {
		log.Fatal(err)
	}

	client := influxdb2.NewClient(fmt.Sprintf("%s://%s:%d", *influxScheme, *influxHost, *influxPort), fmt.Sprintf("%s:%s", *influxUser, *influxPass))

	frames := make(chan []byte)
	go readSerial(s, frames)
	go treatFrames(frames, client)

	interrupt := make(chan os.Signal, 1)
	signal.Notify(interrupt, os.Interrupt, syscall.SIGTERM)
	<-interrupt

	client.Close()
}