Add "power" page

Signed-off-by: Hadi <[email protected]>

internal/power/battery.go

@@ -0,0 +1,175 @@
+package power
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+const powerSupplyPath = "/sys/class/power_supply"
+
+// Battery holds the readable state of one system battery. Peripheral
+// batteries (mouse, keyboard, ...) report scope "Device" in sysfs and are
+// filtered out by ReadBatteries.
+type Battery struct {
+	Name         string
+	Status       string // Charging, Discharging, Full, Not charging, Unknown
+	Capacity     int    // percent, 0-100; -1 if unavailable
+	Health       int    // percent of design capacity still available; -1 if unavailable
+	TimeToEmpty  string // formatted estimate ("2h15m"); empty if not computable
+	TimeToFull   string
+	Technology   string
+	CycleCount   int // -1 if unavailable
+	Manufacturer string
+	Model        string
+}
+
+// ACStatus reports whether external power (AC adapter, USB-PD, dock, ...)
+// is present and delivering power.
+type ACStatus struct {
+	Present bool
+	Online  bool
+}
+
+// ReadBatteries scans /sys/class/power_supply for system battery devices.
+func ReadBatteries() ([]Battery, error) {
+	entries, err := os.ReadDir(powerSupplyPath)
+	if err != nil {
+		return nil, err
+	}
+
+	var batteries []Battery
+	for _, e := range entries {
+		dir := filepath.Join(powerSupplyPath, e.Name())
+		if readAttr(dir, "type") != "Battery" {
+			continue
+		}
+		if readAttr(dir, "scope") == "Device" {
+			continue // peripheral battery (mouse, keyboard, ...), not this machine's
+		}
+		if readAttr(dir, "present") == "0" {
+			continue
+		}
+		batteries = append(batteries, readBattery(dir, e.Name()))
+	}
+	sort.Slice(batteries, func(i, j int) bool { return batteries[i].Name < batteries[j].Name })
+	return batteries, nil
+}
+
+func readBattery(dir, name string) Battery {
+	status := readAttrDefault(dir, "status", "Unknown")
+
+	// Prefer energy_* (µWh); fall back to charge_* (µAh) for fuel gauges
+	// that only report the latter. The ratio math below (percent, hours)
+	// is unit-agnostic as long as full/now/rate come from the same family.
+	full := readAttrInt(dir, "energy_full", 0)
+	design := readAttrInt(dir, "energy_full_design", 0)
+	now := readAttrInt(dir, "energy_now", 0)
+	rate := readAttrInt(dir, "power_now", 0)
+	if full == 0 {
+		full = readAttrInt(dir, "charge_full", 0)
+		design = readAttrInt(dir, "charge_full_design", 0)
+		now = readAttrInt(dir, "charge_now", 0)
+		rate = readAttrInt(dir, "current_now", 0)
+	}
+
+	capacity := readAttrInt(dir, "capacity", -1)
+	if capacity < 0 && full > 0 {
+		capacity = now * 100 / full
+	}
+
+	health := -1
+	if full > 0 && design > 0 {
+		health = full * 100 / design
+	}
+
+	b := Battery{
+		Name:         name,
+		Status:       status,
+		Capacity:     capacity,
+		Health:       health,
+		Technology:   readAttr(dir, "technology"),
+		CycleCount:   readAttrInt(dir, "cycle_count", -1),
+		Manufacturer: readAttr(dir, "manufacturer"),
+		Model:        readAttr(dir, "model_name"),
+	}
+
+	if rate > 0 {
+		switch status {
+		case "Discharging":
+			b.TimeToEmpty = formatHours(float64(now) / float64(rate))
+		case "Charging":
+			if full > now {
+				b.TimeToFull = formatHours(float64(full-now) / float64(rate))
+			}
+		}
+	}
+
+	return b
+}
+
+// ReadAC reports whether any Mains/USB power-supply device is present, and
+// whether at least one of them is actively delivering power. Desktops with
+// no AC-detection device at all get a zero-value, not-present ACStatus.
+func ReadAC() (ACStatus, error) {
+	entries, err := os.ReadDir(powerSupplyPath)
+	if err != nil {
+		return ACStatus{}, err
+	}
+
+	var status ACStatus
+	for _, e := range entries {
+		dir := filepath.Join(powerSupplyPath, e.Name())
+		t := readAttr(dir, "type")
+		if t != "Mains" && t != "USB" {
+			continue
+		}
+		online := readAttr(dir, "online")
+		if online == "" {
+			continue
+		}
+		status.Present = true
+		if online == "1" {
+			status.Online = true
+		}
+	}
+	return status, nil
+}
+
+func formatHours(hours float64) string {
+	if hours <= 0 {
+		return ""
+	}
+	totalMinutes := int(hours*60 + 0.5)
+	return fmt.Sprintf("%dh%02dm", totalMinutes/60, totalMinutes%60)
+}
+
+func readAttr(dir, name string) string {
+	data, err := os.ReadFile(filepath.Join(dir, name)) // #nosec G304 -- dir is enumerated from /sys/class/power_supply, name is a fixed attribute
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(data))
+}
+
+func readAttrDefault(dir, name, def string) string {
+	if v := readAttr(dir, name); v != "" {
+		return v
+	}
+	return def
+}
+
+func readAttrInt(dir, name string, def int) int {
+	v := readAttr(dir, name)
+	if v == "" {
+		return def
+	}
+	n, err := strconv.Atoi(v)
+	if err != nil {
+		return def
+	}
+	return n
+}