// lywsd03mmc-exporter - a Prometheus exporter for the LYWSD03MMC BLE thermometer

// Copyright (C) 2020 Leah Neukirchen <leah@vuxu.org>
// Licensed under the terms of the MIT license, see LICENSE.

package main

import (
	"context"
	"encoding/binary"
	"flag"
	"fmt"
	"log"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/go-ble/ble"
	"github.com/go-ble/ble/examples/lib/dev"
)


// Reading represents a Temperature|Humidity readings
type Reading struct {
	Temperature float64
	Humidity    float64
}

const Sensor = "LYWSD03MMC"
const TelinkVendorPrefix = "a4:c1:38"

var EnvironmentalSensingUUID = ble.UUID16(0x181a)
var XiaomiIncUUID = ble.UUID16(0xfe95)

const ExpiryAtc = 2.5 * 10 * time.Second
const ExpiryStock = 2.5 * 10 * time.Minute
const ExpiryConn = 2.5 * 10 * time.Second

var expirers = make(map[string]*time.Timer)
var expirersLock sync.Mutex



var (
	configFile = flag.String("config_file", "config.ini", "Config file location")
)

var config, ERR = NewConfig(*configFile)

func bump(mac string, expiry time.Duration) {
	expirersLock.Lock()
	if t, ok := expirers[mac]; ok {
		t.Reset(expiry)
	} else {
		expirers[mac] = time.AfterFunc(expiry, func() {
			fmt.Printf("expiring %s\n", mac)
			expirersLock.Lock()
			delete(expirers, mac)
			expirersLock.Unlock()
		})
	}
	expirersLock.Unlock()
}

func macWithColons(mac string) string {
	return strings.ToUpper(fmt.Sprintf("%s:%s:%s:%s:%s:%s",
		mac[0:2],
		mac[2:4],
		mac[4:6],
		mac[6:8],
		mac[8:10],
		mac[10:12]))
}

func macWithoutColons(mac string) string {
	return strings.ReplaceAll(strings.ToUpper(mac), ":", "")
}

func decodeSign(i uint16) int {
	if i < 32768 {
		return int(i)
	} else {
		return int(i) - 65536
	}
}

func registerData(data []byte, frameMac string, rssi int) {
	if len(data) != 13 {
		return
	}

	mac := fmt.Sprintf("%X", data[0:6])

	if mac != frameMac {
		return
	}

	temp := float64(decodeSign(binary.BigEndian.Uint16(data[6:8]))) / 10.0
	hum := float64(data[8])
	batp := float64(data[9])
	batv := float64(binary.BigEndian.Uint16(data[10:12])) / 1000.0
	//frame := float64(data[12])

	bump(mac, ExpiryAtc)

	logTemperature(mac, temp)
	logHumidity(mac, hum)
	logBatteryPercent(mac, batp)
	logVoltage(mac, batv)
	logRssi(mac, rssi)
	var r = Reading{temp, hum}
	config.MQTT.Publish(mac,&r)
}

func advHandler(a ble.Advertisement) {
	mac := strings.ReplaceAll(strings.ToUpper(a.Addr().String()), ":", "")

	for _, sd := range a.ServiceData() {
		if sd.UUID.Equal(EnvironmentalSensingUUID) {
			registerData(sd.Data, mac, a.RSSI())
		}
	}
}


func logTemperature(mac string, temp float64) {
	log.Printf("%s thermometer_temperature_celsius %.1f\n", mac, temp)
}

func logHumidity(mac string, hum float64) {
	log.Printf("%s thermometer_humidity_ratio %.0f\n", mac, hum)
}

func logVoltage(mac string, batv float64) {
	log.Printf("%s thermometer_battery_volts %.3f\n", mac, batv)
}

func logBatteryPercent(mac string, batp float64) {
	log.Printf("%s thermometer_battery_ratio %.0f\n", mac, batp)
}

func logRssi(mac string, rssi int) {
	log.Printf("%s thermometer_rssi %d\n", mac, rssi)
}

func decodeAtcTemp(mac string) func(req []byte) {
	return func(req []byte) {
		temp := float64(decodeSign(binary.LittleEndian.Uint16(req[0:2]))) / 10.0
		bump(mac, ExpiryConn)
		logTemperature(mac, temp)
	}
}

func decodeAtcHumidity(mac string) func(req []byte) {
	return func(req []byte) {
		hum := float64(binary.LittleEndian.Uint16(req[0:2])) / 100.0
		bump(mac, ExpiryConn)
		logHumidity(mac, hum)
	}
}

func decodeAtcBattery(mac string) func(req []byte) {
	return func(req []byte) {
		batp := float64(req[0])
		bump(mac, ExpiryConn)
		logBatteryPercent(mac, batp)
	}
}

// ToString converts a Reading to a string
func (r *Reading) String() string {
	return fmt.Sprintf("Temperature: %.04f; Humidity: %.04f", r.Temperature, r.Humidity)
}


func main() {
	flag.Parse()
	//config, err := NewConfig(*configFile)
	//if err != nil {
	//	log.Fatal("Unable to parse configuration")
	//}

	log.Printf("MQTT broker: %s", config.MQTT.Server())
	if err := config.MQTT.Connect("xiaomi"); err != nil {
		log.Print("[main] Unable to connect to MQTT broker")
	}


	deviceID := flag.Int("i", 0, "use device hci`N`")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr,
			"Usage: %s [FLAGS...] \n", os.Args[0])
		flag.PrintDefaults()
	}
	flag.Parse()

	device, err := dev.NewDevice("default", ble.OptDeviceID(*deviceID))
	if err != nil {
		log.Fatal("oops: ", err)
	}

	ble.SetDefaultDevice(device)

	ctx := ble.WithSigHandler(context.Background(), nil)

	telinkVendorFilter := func(a ble.Advertisement) bool {
		return strings.HasPrefix(a.Addr().String(), TelinkVendorPrefix)
	}
	err = ble.Scan(ctx, true, advHandler, telinkVendorFilter)
	if err != nil {
		log.Fatal("oops: %s", err)
	}
}