package main

import (

	"encoding/json"

	"fmt"

	"io"

	"io/ioutil"

	"log"

	flag "github.com/docker/docker/pkg/mflag"

	"github.com/tarm/serial"

)

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 fetchData(dev string) (items []measurement, err error) {

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

	var s *serial.Port

	s, err = serial.OpenPort(c)

	if err != nil {

		return items, err

	}

	// =================== Handshake =====================

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

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

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

	n, err := s.Write(q)

	if err != nil {

		return items, err

	}

	buf := make([]byte, 128)

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

	if err != nil {

		return items, err

	}

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

		log.Println("Handshake successful.")

	} else {

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

		s.Close()

		return items, fmt.Errorf("handshake failed")

	}

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

	q = []byte("\xa4")

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

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

	n, err = s.Write(q)

	if err != nil {

		return items, err

	}

	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 {

		return items, err

	}

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

	if err != nil {

		return items, err

	}

	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 items, fmt.Errorf("no measurement found")

	}

	// =================== Records =====================

	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 {

			return items, err

		}

		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

		items = append(items, data)

	}

	s.Close()

	return items, nil

}

func loadFromJSONFile(filename string) (items []measurement, err error) {

	data, err := ioutil.ReadFile(filename)

	if err != nil {

		return items, err

	}

	err = json.Unmarshal(data, &items)

	return items, err

}

func mergeItems(newItems, oldItems []measurement) []measurement {

	var result []measurement

	var j int

	// TODO: Would be better to compare dates and merge chronologically...

	for _, nItem := range newItems {

		result = append(result, nItem)

		if j+1 <= len(oldItems) && nItem == oldItems[j] {

			j++

		}

	}

	if j+1 <= len(oldItems) {

		result = append(result, oldItems[j:]...)

	}

	return result

}

func main() {

	inFile := flag.String([]string{"-input-file", "i"}, "", "Input JSON file")

	outFile := flag.String([]string{"-output-file", "o"}, "", "Output JSON file")

	format := flag.String([]string{"-format", "f"}, "", "Output format (csv, json)")

	avg := flag.Bool([]string{"-average", "a"}, false, "Compute average")

	merge := flag.Bool([]string{"-merge", "m"}, false,

		"Try to merge input JSON file with fetched data")

	device := flag.String([]string{"-device", "d"}, "/dev/ttyUSB0", "Serial device")

	flag.Parse()

	switch *format {

	case "":

		if *outFile == "" {

			*format = "csv"

		}

		break

	case "json", "csv":

		break

	default:

		log.Fatal("Unknown output format.  Possible choices are csv, json.")

	}

	var items []measurement

	if *inFile == "" {

		// Read from device

		if items, err = fetchData(*device); err != nil {

			log.Fatal(err)

		}

	} else {

		// Read from file

		var fileItems []measurement

		if fileItems, err = loadFromJSONFile(*inFile); err != nil {

			log.Fatal(err)

		}

		if *merge {

			if items, err = fetchData(*device); err != nil {

				log.Fatal(err)

			}

			items = mergeItems(items, fileItems)

		} else {

			items = fileItems

		}

	}

	if *limit > 0 && len(items) > int(*limit) {

		items = items[0:*limit]

	}

	var avgMeasure measurement

	var avgCount int

	for i, data := range items {

		if *format == "csv" {

			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)

		}

		avgMeasure.Systolic += data.Systolic

		avgMeasure.Diastolic += data.Diastolic

		avgMeasure.Pulse += data.Pulse

		avgCount++

	}

	if *avg && avgCount > 0 {

		avgMeasure.Systolic /= avgCount

		avgMeasure.Diastolic /= avgCount

		avgMeasure.Pulse /= avgCount

		fmt.Printf("Average: %d;%d;%d\n", avgMeasure.Systolic,

			avgMeasure.Diastolic, avgMeasure.Pulse)

	}

	if *format == "json" || *outFile != "" {

		rawJSON, err := json.MarshalIndent(items, "", "  ")

		if err != nil {

			log.Fatal("Error:", err)

		}

		if *format == "json" {

			fmt.Println(string(rawJSON))

		}

		if *outFile != "" {

			err = ioutil.WriteFile(*outFile, rawJSON, 0600)

			if err != nil {

				log.Println("Could not write output file:", err)

			}

		}

	}

}