package main

import (
	"bufio"
	"encoding/json"
	"fmt"
	"github.com/tarm/serial"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

type SensorData struct {
	WeightARaw string `json:"weight_a_raw"`
	WeightBRaw string `json:"weight_b_raw"`
}

// returns last line of output
func sendCommand(p *serial.Port, command string) string {
	fmt.Printf("%s\n", command)
	var last_line string = ""
	p.Flush()
	_, err := p.Write([]byte(command))
	if err != nil {
		log.Fatal(err)
	}
	buf := make([]byte, 1024)

	time.Sleep(500 * time.Millisecond)

	n, _ := p.Read(buf)
	if n > 0 {
		last_line_arr := strings.Split(string(buf[:n]), "\n")
		//fmt.Printf("AAA: %+q\n", last_line_arr)
		last_line = last_line_arr[len(last_line_arr)-2]

		fmt.Print(string(buf[:n]))
	}
	return last_line
}

// returns output
func sendCommandJSON(p *serial.Port, command string) string {
	fmt.Printf("%s\n", command)
	var res string = ""
	p.Flush()
	_, err := p.Write([]byte(command))
	if err != nil {
		log.Fatal(err)
	}
	buf := make([]byte, 1024)

	time.Sleep(3000 * time.Millisecond)

	n, _ := p.Read(buf)
	if n > 0 {
		res = string(buf[:n-1])
	}
	return res
}

func getDevEui(p *serial.Port) string {
	var reply = sendCommand(p, "AT+ChipID=?")
	//fmt.Printf("XXX%sYYY\n",reply)
	if len(reply) >= 20 {
		return "0000" + reply[8:20]
	} else {
		return ""
	}
}

func ReadSensorData(p *serial.Port) SensorData {
	var reply = sendCommandJSON(p, "AT+READ_SENSORS=?")
	fmt.Printf("XXX%sYYY\n", reply)

	var data SensorData
	json.Unmarshal([]byte(reply), &data)
	//fmt.Printf("%v \n", data)

	//fmt.Printf("weight_a_raw: %s\n", data.WeightARaw)
	//fmt.Printf("weight_b_raw: %s\n", data.WeightBRaw)

	return data
}

func readSerial(p *serial.Port) {
	p.Flush()
	buf := make([]byte, 32)

	time.Sleep(200 * time.Millisecond)
	n, _ := p.Read(buf)
	for n > 0 {
		// ignoring error as EOF raises error on Linux
		reply := string(buf[:n])
		fmt.Print(reply)
		n, _ = p.Read(buf)
	}
}

func main() {
	if len(os.Args) != 3 {
		fmt.Println("usage: " + filepath.Base(os.Args[0]) + " <SerialDevice> <calibration_weight_in_gram>")
		os.Exit(1)
	}

	serialdev := os.Args[1]
	calWeightS := os.Args[2]
	calWeight, _ := strconv.Atoi(calWeightS)

	c := &serial.Config{Name: serialdev, Baud: 115200, ReadTimeout: time.Second * 1}
	s, err := serial.OpenPort(c)
	if err != nil {
		log.Fatal("Problem mit Serial Interface")
	}

	sendCommand(s, "AT+XXX")
	devEui := getDevEui(s)
	reader := bufio.NewReader(os.Stdin)
	if devEui != "" {
		fmt.Println("Hit Return when no weight is on scale (neither on A not on B)")
		reader.ReadString('\n')
		sendCommand(s, "AT+XXX")
		sensorData := ReadSensorData(s)
		fmt.Printf("%v\n", sensorData)
		a0, _ := strconv.Atoi(sensorData.WeightARaw)
		b0, _ := strconv.Atoi(sensorData.WeightBRaw)
		sendCommand(s, "AT+CAL_A_0="+sensorData.WeightARaw)
		sendCommand(s, "AT+CAL_B_0="+sensorData.WeightBRaw)
		fmt.Println("Put Weight on Scale A, then hit Return")
		reader.ReadString('\n')
		sendCommand(s, "AT+XXX")
		sensorData = ReadSensorData(s)
		aW, _ := strconv.Atoi(sensorData.WeightARaw)
		fmt.Println("Put Weight on Scale B, then hit Return")
		reader.ReadString('\n')
		sendCommand(s, "AT+XXX")
		sensorData = ReadSensorData(s)
		bW, _ := strconv.Atoi(sensorData.WeightBRaw)
		calA := float64(aW-a0) / float64(calWeight)
		calB := float64(bW-b0) / float64(calWeight)
		sendCommand(s, "AT+CAL_A_FACTOR="+fmt.Sprintf("%f", calA))
		sendCommand(s, "AT+CAL_B_FACTOR="+fmt.Sprintf("%f", calB))
		sendCommand(s, "AT+READ_CONFIG=?")
		sendCommand(s, "AT+RESET=1")
		readSerial(s)
	} else {
		log.Fatal("Could not get devEui (that is: ChipID)")
	}
}