src

temp.go (2299B)

---

 package temp
 
 import (
 	"context"
 	"encoding/json"
 	"fmt"
 	"os/exec"
 	"strings"
 )
 
 // Sensor describes a single temperature sensor to be read.
 type Sensor struct {
 	Label string   `json:"label"`
 	Path  []string `json:"path"`
 }
 
 // Config holds the configuration for the temp block.
 type Config struct {
 	Sensors []Sensor `json:"sensors"`
 }
 
 type Block struct {
 	config Config
 }
 
 func New(c Config) *Block {
 	return &Block{config: c}
 }
 
 func (b *Block) Name() string {
 	return "temp"
 }
 
 func (b *Block) Render(ctx context.Context) (string, error) {
 	out, err := exec.CommandContext(ctx, "sensors", "-j").Output()
 	if err != nil {
 		return "", fmt.Errorf("exec sensors failed: %v", err)
 	}
 	if len(b.config.Sensors) == 0 {
 		return "", nil
 	}
 
 	var parts = make([]string, 0, len(b.config.Sensors))
 	for _, sensor := range b.config.Sensors {
 		temp, err := parse(out, sensor.Path)
 		if err != nil {
 			return "", fmt.Errorf(
 				"failed to get temp for %v: %w",
 				sensor.Path, err,
 			)
 		}
 
 		var renderedSensor string
 		if sensor.Label != "" {
 			renderedSensor = fmt.Sprintf(
 				"%s %.0f℃", sensor.Label, temp,
 			)
 		} else {
 			renderedSensor = fmt.Sprintf("%.0f℃", temp)
 		}
 		parts = append(parts, renderedSensor)
 	}
 
 	return strings.Join(parts, " "), nil
 }
 
 // parse traverses the json data using the given path to find a temperature
 // value.
 func parse(data []byte, path []string) (float64, error) {
 	if len(path) == 0 {
 		return 0, fmt.Errorf("sensor path cannot be empty")
 	}
 
 	// We start with the full JSON output.
 	var current = json.RawMessage(data)
 
 	// For each key in the path, we dive one level deeper into the JSON
 	// structure.
 	for i, key := range path {
 		var m map[string]json.RawMessage
 		if err := json.Unmarshal(current, &m); err != nil {
 			return 0, fmt.Errorf(
 				"failed to unmarshal object at path segment %d ('%s'): %w",
 				i, key, err,
 			)
 		}
 
 		var ok bool
 		current, ok = m[key]
 		if !ok {
 			return 0, fmt.Errorf(
 				"key not found at path segment %d ('%s')",
 				i, key,
 			)
 		}
 	}
 
 	// After the loop, 'current' holds the raw JSON for the temperature
 	// value.
 	var temp float64
 	if err := json.Unmarshal(current, &temp); err != nil {
 		return 0, fmt.Errorf(
 			"final value at path %v is not a number: %w", path, err,
 		)
 	}
 
 	return temp, nil
 }