sim-modem/api/modem/gps/gps.go

package gps

import (
	"fmt"
	"io"
	"log"
	"strings"

	"github.com/CGSG-2021-AE4/modem-test/api/modem/at"
)

type gps struct {
	logger *log.Logger
	port   at.Port
	data   Data
}

type Gps interface {
	Init() error
	Update() error

	GetData() Data
	GetStatus() (Status, error)

	io.Closer
}

func New(logger *log.Logger, port at.Port) Gps {
	return &gps{
		logger: logger,
		port:   port,
	}
}

func (g *gps) Init() error {
	if !g.port.IsConnected() {
		return fmt.Errorf("at port is not connected")
	}
	return nil
}

func (g *gps) Update() error {
	if err := g.switchGpsMode(true); err != nil {
		return fmt.Errorf("try to GPS mode: %w", err)
	}
	defer g.switchGpsMode(false)

	resp, err := g.port.Send("AT+CGPSINFO")
	if err != nil {
		return fmt.Errorf("receive GPS data: %w", err)
	}
	if !resp.Check() {
		return fmt.Errorf("get GPS info: error response: %s", resp)
	}
	if err := g.data.decode(strings.Split(strings.Replace(resp.RmFront("+CGPSINFO:").String(), "\r", "", -1), "\n")[0]); err != nil {
		return fmt.Errorf("decode: %w", err)
	}
	return nil
}

func (g *gps) GetData() Data {
	return g.data
}

func (g *gps) Close() error {
	return nil
}

func (g *gps) switchGpsMode(on bool) error {
	onStr := "0"
	if on {
		onStr = "1"
	}

	// Reset input
	if err := g.port.SerialPort().ResetInputBuffer(); err != nil {
		return fmt.Errorf("reset input buffer: %w", err)
	}
	// Reset output
	if err := g.port.SerialPort().ResetOutputBuffer(); err != nil {
		return fmt.Errorf("reset output buffer: %w", err)
	}

	// Check gps mode status
	resp, err := g.port.Send("AT+CGPS?")
	if err != nil {
		return fmt.Errorf("make at ask: %w", err)
	}
	if !resp.Check() {
		return fmt.Errorf("get GPS mode: error response: %s", resp)
	}
	ans := strings.Replace(strings.Split(strings.Split(resp.RmFront("+CGPS:").String(), "\n")[0], ",")[0], " ", "", -1)
	if ans == onStr {
		return nil
	}

	// Modem is not in GPS mode
	resp, err = g.port.Send("AT+CGPS=" + onStr)
	if err != nil {
		return fmt.Errorf("set GPS mode: %w", err)
	}
	if !resp.Check() {
		return fmt.Errorf("set GPS mode: error response: %s", resp)
	}
	return nil
}