Phase 3+4: systemd generator, install, active, status

- systemd/generator.go: build .service file content from Unit
- systemd/manager.go: install/uninstall/enable/disable/status via systemctl
- cmd/install.go: write unit files, --dry-run flag, remove disabled units
- cmd/active.go: enable + start units in order
- cmd/status.go: summary table with name/runtime/user/enabled/installed/state

systemd/generator.go

@@ -0,0 +1,105 @@
+package systemd
+
+import (
+	"fmt"
+	"strings"
+	"text/template"
+
+	"github.com/warkanum/unitdore/config"
+)
+
+const systemUnitTemplate = `# /etc/systemd/system/{{.ServiceName}}
+# Generated by unitdore — do not edit manually
+
+[Unit]
+Description=Unitdore: {{.Unit.Name}} ({{.Unit.Runtime}})
+After=network.target
+
+[Service]
+Type=simple
+ExecStart={{.ExecStart}}
+ExecStop={{.ExecStop}}
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=multi-user.target
+`
+
+const userUnitTemplate = `# ~/.config/systemd/user/{{.ServiceName}}
+# Generated by unitdore — do not edit manually
+
+[Unit]
+Description=Unitdore: {{.Unit.Name}} ({{.Unit.Runtime}})
+After=default.target
+
+[Service]
+Type=simple
+ExecStart={{.ExecStart}}
+ExecStop={{.ExecStop}}
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=default.target
+`
+
+type templateData struct {
+	ServiceName string
+	Unit        config.Unit
+	ExecStart   string
+	ExecStop    string
+}
+
+// ServiceName returns the systemd service name for a unit.
+func ServiceName(u config.Unit) string {
+	return fmt.Sprintf("unitdore-%s.service", u.Name)
+}
+
+// Generate produces the .service file content for a unit.
+func Generate(u config.Unit) (string, error) {
+	execStart, execStop := buildExecCommands(u)
+
+	data := templateData{
+		ServiceName: ServiceName(u),
+		Unit:        u,
+		ExecStart:   execStart,
+		ExecStop:    execStop,
+	}
+
+	tmplStr := systemUnitTemplate
+	if u.User != "" {
+		tmplStr = userUnitTemplate
+	}
+
+	tmpl, err := template.New("unit").Parse(tmplStr)
+	if err != nil {
+		return "", fmt.Errorf("parsing template: %w", err)
+	}
+
+	var buf strings.Builder
+	if err := tmpl.Execute(&buf, data); err != nil {
+		return "", fmt.Errorf("rendering template: %w", err)
+	}
+	return buf.String(), nil
+}
+
+func buildExecCommands(u config.Unit) (start, stop string) {
+	// If a custom command is provided, use it directly
+	if u.Command != "" {
+		return u.Command, ""
+	}
+
+	switch u.Runtime {
+	case "podman":
+		start = fmt.Sprintf("/usr/bin/podman start -a %s", u.Name)
+		stop = fmt.Sprintf("/usr/bin/podman stop %s", u.Name)
+	case "docker":
+		start = fmt.Sprintf("/usr/bin/docker start %s", u.Name)
+		stop = fmt.Sprintf("/usr/bin/docker stop %s", u.Name)
+	default:
+		start = fmt.Sprintf("/usr/bin/%s start %s", u.Runtime, u.Name)
+		stop = fmt.Sprintf("/usr/bin/%s stop %s", u.Runtime, u.Name)
+	}
+	return start, stop
+}

systemd/manager.go

@@ -0,0 +1,145 @@
+package systemd
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/warkanum/unitdore/config"
+)
+
+const systemUnitDir = "/etc/systemd/system"
+
+// UnitPath returns the filesystem path where the .service file should be written.
+func UnitPath(u config.Unit) (string, error) {
+	if u.User == "" {
+		return filepath.Join(systemUnitDir, ServiceName(u)), nil
+	}
+	// Rootless: write to the user's systemd config dir
+	home, err := userHomeDir(u.User)
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(home, ".config", "systemd", "user", ServiceName(u)), nil
+}
+
+// Install writes the .service file for a unit and reloads systemd.
+func Install(u config.Unit) error {
+	content, err := Generate(u)
+	if err != nil {
+		return err
+	}
+
+	path, err := UnitPath(u)
+	if err != nil {
+		return err
+	}
+
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
+		return fmt.Errorf("creating unit dir: %w", err)
+	}
+
+	if err := os.WriteFile(path, []byte(content), 0644); err != nil {
+		return fmt.Errorf("writing unit file: %w", err)
+	}
+
+	return daemonReload(u.User)
+}
+
+// Uninstall removes the .service file for a unit and reloads systemd.
+func Uninstall(u config.Unit) error {
+	path, err := UnitPath(u)
+	if err != nil {
+		return err
+	}
+
+	if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("removing unit file: %w", err)
+	}
+
+	return daemonReload(u.User)
+}
+
+// Enable enables and starts a unit.
+func Enable(u config.Unit) error {
+	return systemctl(u.User, "enable", "--now", ServiceName(u))
+}
+
+// Disable disables and stops a unit.
+func Disable(u config.Unit) error {
+	return systemctl(u.User, "disable", "--now", ServiceName(u))
+}
+
+// Status returns the ActiveState of a unit ("active", "inactive", "failed", "unknown").
+func Status(u config.Unit) string {
+	args := []string{"show", "-p", "ActiveState", "--value", ServiceName(u)}
+	var out []byte
+	var err error
+
+	if u.User == "" {
+		out, err = exec.Command("systemctl", args...).Output()
+	} else {
+		out, err = runAsUser(u.User, "systemctl", append([]string{"--user"}, args...)...)
+	}
+	if err != nil {
+		return "unknown"
+	}
+	return strings.TrimSpace(string(out))
+}
+
+// IsInstalled returns true if the unit file exists on disk.
+func IsInstalled(u config.Unit) bool {
+	path, err := UnitPath(u)
+	if err != nil {
+		return false
+	}
+	_, err = os.Stat(path)
+	return err == nil
+}
+
+// --- helpers ---
+
+func daemonReload(user string) error {
+	if user == "" {
+		return systemctl("", "daemon-reload")
+	}
+	return systemctl(user, "daemon-reload")
+}
+
+func systemctl(user string, args ...string) error {
+	if user == "" {
+		cmd := exec.Command("systemctl", args...)
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+		return cmd.Run()
+	}
+	return runAsUserCmd(user, "systemctl", append([]string{"--user"}, args...)...)
+}
+
+func runAsUser(user string, bin string, args ...string) ([]byte, error) {
+	full := append([]string{"-u", user, "--", bin}, args...)
+	return exec.Command("runuser", full...).Output()
+}
+
+func runAsUserCmd(user string, bin string, args ...string) error {
+	full := append([]string{"-u", user, "--", bin}, args...)
+	cmd := exec.Command("runuser", full...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+func userHomeDir(user string) (string, error) {
+	out, err := exec.Command("getent", "passwd", user).Output()
+	if err != nil {
+		return "", fmt.Errorf("looking up user %s: %w", user, err)
+	}
+	// passwd format: name:pass:uid:gid:gecos:home:shell
+	parts := strings.Split(strings.TrimSpace(string(out)), ":")
+	if len(parts) < 6 {
+		return "", fmt.Errorf("unexpected passwd entry for %s", user)
+	}
+	return parts[5], nil
+}