Add "power" page

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

internal/power/profiles.go

@@ -0,0 +1,103 @@
+// Package power reads and controls the active power profile (via
+// powerprofilesctl / power-profiles-daemon) and reports battery/AC status.
+// Profile control shells out to a CLI tool, in the same spirit as the
+// bluetooth and audio packages; battery status has no universally-installed
+// CLI equivalent, so it's read directly from /sys/class/power_supply.
+package power
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+var ErrNotFound = errors.New("powerprofilesctl not found in PATH")
+
+const defaultTimeout = 15 * time.Second
+
+// Profile is one entry from `powerprofilesctl list`.
+type Profile struct {
+	Name   string
+	Active bool
+}
+
+// CheckAvailable reports whether powerprofilesctl is installed and
+// power-profiles-daemon is reachable. Call it before using the rest of
+// this file's functions.
+func CheckAvailable() error {
+	if _, err := exec.LookPath("powerprofilesctl"); err != nil {
+		return ErrNotFound
+	}
+	_, err := run("get")
+	return err
+}
+
+// ListProfiles returns the available profiles in the order reported by
+// powerprofilesctl, each flagged with whether it's currently active.
+func ListProfiles() ([]Profile, error) {
+	out, err := run("list")
+	if err != nil {
+		return nil, err
+	}
+
+	var profiles []Profile
+	for _, line := range strings.Split(out, "\n") {
+		// Top-level profile entries are indented two spaces (or "* " when
+		// active); their attribute lines (Driver:, Degraded:, ...) are
+		// indented four, so those are skipped here.
+		if line == "" || strings.HasPrefix(line, "    ") {
+			continue
+		}
+
+		active := false
+		trimmed := line
+		switch {
+		case strings.HasPrefix(trimmed, "* "):
+			active = true
+			trimmed = trimmed[2:]
+		case strings.HasPrefix(trimmed, "  "):
+			trimmed = trimmed[2:]
+		default:
+			continue
+		}
+
+		name := strings.TrimSuffix(trimmed, ":")
+		if name == "" {
+			continue
+		}
+		profiles = append(profiles, Profile{Name: name, Active: active})
+	}
+	return profiles, nil
+}
+
+// SetActive switches the active power profile.
+func SetActive(name string) error {
+	_, err := run("set", name)
+	return err
+}
+
+func run(args ...string) (string, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTimeout)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, "powerprofilesctl", args...) // #nosec G204 -- args are fixed powerprofilesctl subcommands or profile names read back from `powerprofilesctl list`, never shell-interpreted
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	if err := cmd.Run(); err != nil {
+		if errors.Is(err, exec.ErrNotFound) {
+			return "", ErrNotFound
+		}
+		msg := strings.TrimSpace(stderr.String())
+		if msg == "" {
+			msg = err.Error()
+		}
+		return "", fmt.Errorf("powerprofilesctl %s: %s", strings.Join(args, " "), msg)
+	}
+	return stdout.String(), nil
+}