package main

import (

	"io"

	"fmt"

	"log"

	"github.com/tarm/goserial"

)

type measurement struct {

	header    int

	systolic  int

	diastolic int

	pulse     int

	month     int

	day       int

	hour      int

	minute    int

	year      int

}

func getData(s io.ReadWriteCloser, buf []byte, size int) (int, error) {

	t := 0

	b := buf

	for t < size {

		n, err := s.Read(b[t:])

		if err != nil {

			log.Fatal(err) // XXX

			return t, err

		}

		//log.Printf("(%d bytes) %q\n", n, b[t:t+1])

		t = t + n

	}

	return t, nil

}

func main() {

	c := &serial.Config{Name: "/dev/ttyUSB0", Baud: 4800}

	s, err := serial.OpenPort(c)

	if err != nil {

		log.Fatal(err)

		return

	}

	q := []byte("\xaa")

	//log.Printf("Query: %q\n", q)

	log.Println("Starting handshake...")

	n, err := s.Write(q)

	if err != nil {

		log.Fatal(err)

		return

	}

	buf := make([]byte, 128)

	n, err = getData(s, buf, 1)

	if err != nil {

		log.Fatal(err)

		return

	}

	if n == 1 && buf[0] == '\x55' {

		log.Println("Handshake successful.")

	} else {

		log.Printf("(%d bytes) %q\n", n, buf[:n])

		s.Close()

		return

	}

	// =================== Desc =====================

	q = []byte("\xa4")

	//log.Printf("Query: %q\n", q)

	log.Println("Requesting device description...")

	n, err = s.Write(q)

	if err != nil {

		log.Fatal(err)

		return

	}

	n, err = getData(s, buf, 32)

	log.Printf("DESC> %q\n", buf[:n])

	// =================== Count =====================

	q = []byte("\xa2")

	//log.Printf("Query: %q\n", q)

	log.Println("Requesting data counter...")

	n, err = s.Write(q)

	if err != nil {

		log.Fatal(err)

		return

	}

	n, err = getData(s, buf, 1)

	if err != nil {

		log.Fatal(err)

		return

	}

	var nRecords int

	if n == 1 {

		log.Printf("%d item(s) available.", buf[0])

		nRecords = int(buf[0])

	} else {

		log.Printf("(%d bytes) %q\n", n, buf[:n])

		return

	}

	for i := 0; i < nRecords; i++ {

		q = []byte{'\xa3', uint8(i + 1)}

		//log.Printf("Query: %q\n", q)

		//log.Printf("Requesting measurement %d...", i+1)

		n, err = s.Write(q)

		if err != nil {

			log.Fatal(err)

			return

		}

		n, err = getData(s, buf, 9)

		//log.Printf("DESC> %q\n", buf[:n])

		var data measurement

		data.header = int(buf[0])

		data.systolic = int(buf[1]) + 25

		data.diastolic = int(buf[2]) + 25

		data.pulse = int(buf[3])

		data.month = int(buf[4])

		data.day = int(buf[5])

		data.hour = int(buf[6])

		data.minute = int(buf[7])

		data.year = int(buf[8]) + 2000

		fmt.Printf("%d;%x;%d-%02d-%02d %02d:%02d;%d;%d;%d\n",

			i+1, data.header,

			data.year, data.month, data.day,

			data.hour, data.minute,

			data.systolic, data.diastolic, data.pulse)

	}

	s.Close()

}