home-sensors/internal/sensors/sensors.go

package sensors

import (
	"bufio"
	"context"
	"os/exec"
	"strconv"
	"strings"
	"sync"
	"time"

	pb "github.com/chathaway-codes/home-sensors/v2/gen"
	"github.com/chathaway-codes/home-sensors/v2/internal/pipespy"
	"github.com/chathaway-codes/home-sensors/v2/internal/watcher/config"
	"github.com/google/uuid"
	"github.com/rs/zerolog/log"
)

var Default = &Mod{}

type Sensors struct {
	mu         sync.Mutex
	ctx        context.Context
	readCmd    *exec.Cmd
	cancelFunc func()
	ticker     time.Ticker

	listeners map[string]chan<- *pb.Sample
}

func New(cfg *config.Config) (*Sensors, error) {
	ctx, cancelFunc := context.WithCancel(context.Background())
	readCmd := exec.CommandContext(ctx, cfg.SensorCmd.Binary, cfg.SensorCmd.Arguments...)

	ticker := time.NewTicker(time.Duration(cfg.SensorRateMS) * time.Millisecond)
	return &Sensors{
		ctx:        ctx,
		cancelFunc: cancelFunc,
		readCmd:    readCmd,
		ticker:     *ticker,
		// it would be better if sensors.Run handled sending to the server; to do that,
		// it needs a connection and the auth token. I don't have a clean way of getting that
		// right now.
		listeners: make(map[string]chan<- *pb.Sample),
	}, nil
}

func (v *Sensors) Run() {
	pipe := pipespy.New()
	snoop := pipe.Add(pipespy.NewCmd(v.readCmd)).Snoop()
	defer snoop.Close()

	cleanUp := pipe.Start()
	defer func() {
		errs := cleanUp()
		for _, err := range errs {
			log.Err(err).Send()
		}
	}()

	scanner := bufio.NewScanner(snoop)
	for scanner.Scan() {
		line := scanner.Text()
		parts := strings.Split(line, " ")
		if len(parts) != 3 {
			log.Error().Str("line", line).Msg("malformed line; expected 3 floats: humidity pressure temperature_c")
		}
		humidity, err := strconv.ParseFloat(parts[0], 64)
		if err != nil {
			log.Error().Err(err).Str("val", parts[0]).Msg("failed to parse humidity")
		}
		pressure, err := strconv.ParseFloat(parts[1], 64)
		if err != nil {
			log.Error().Err(err).Str("val", parts[1]).Msg("failed to parse pressure")
		}
		temperatureC, err := strconv.ParseFloat(parts[2], 64)
		if err != nil {
			log.Error().Err(err).Str("val", parts[2]).Msg("failed to parse temperature_c")
		}

		select {
		case <-v.ticker.C:
			func() {
				v.mu.Lock()
				defer v.mu.Unlock()

				samples := []*pb.Sample{
					{
						Type:    pb.Sample_HUMIDITY,
						Reading: humidity,
					},
					{
						Type:    pb.Sample_PRESSURE,
						Reading: pressure,
					},
					{
						Type:    pb.Sample_TEMPERATURE_C,
						Reading: temperatureC,
					},
				}

				for _, listener := range v.listeners {
					for _, sample := range samples {
						listener <- sample
					}
				}
			}()
		default:
			// do nothing
		}
	}
}

// Join will connect to a running stream.
func (v *Sensors) Join() (<-chan *pb.Sample, func()) {
	v.mu.Lock()
	defer v.mu.Unlock()

	myID := uuid.New().String()
	ch := make(chan *pb.Sample)
	v.listeners[myID] = ch

	return ch, func() {
		v.mu.Lock()
		defer v.mu.Unlock()

		delete(v.listeners, myID)
	}
}

// Done stops the processing.
func (v *Sensors) Done() {
	v.cancelFunc()
}

type Mod struct{}

func (m *Mod) Get() (*Sensors, error) {
	cfg, err := config.Default.Get()
	if err != nil {
		return nil, err
	}
	return New(cfg)
}