daemon: create daemon management interface

Create 'DaemonProvider' interface for creating and managing daemon
processes, to eventually be used by the 'web-server' subcommand to manage a
web server daemon.

Because daemon process management is dependent on the operating system/tools
available, initially create two types to implement the interface: one for
'launchd' (MacOS) and one for 'systemd' (Linux). The functions, for now, all
return "not implemented" errors but will be implemented in later patches.

Finally, add a 'NewDaemonProvider' to create the appropriate daemon provider
implementation based on the operating system.

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

internal/daemon/daemon.go

@@ -0,0 +1,32 @@
+package daemon
+
+import (
+	"fmt"
+	"runtime"
+)
+
+type DaemonConfig struct {
+	Label   string
+	Program string
+}
+
+type DaemonProvider interface {
+	Create(config *DaemonConfig, force bool) error
+
+	Start(label string) error
+
+	Stop(label string) error
+}
+
+func NewDaemonProvider() (DaemonProvider, error) {
+	switch thisOs := runtime.GOOS; thisOs {
+	case "linux":
+		// Use systemd/systemctl
+		return NewSystemdProvider(), nil
+	case "darwin":
+		// Use launchd/launchctl
+		return NewLaunchdProvider(), nil
+	default:
+		return nil, fmt.Errorf("cannot configure daemon handler for OS '%s'", thisOs)
+	}
+}

internal/daemon/launchd.go

@@ -0,0 +1,23 @@
+package daemon
+
+import (
+	"fmt"
+)
+
+type launchd struct{}
+
+func NewLaunchdProvider() DaemonProvider {
+	return &launchd{}
+}
+
+func (l *launchd) Create(config *DaemonConfig, force bool) error {
+	return fmt.Errorf("not implemented")
+}
+
+func (l *launchd) Start(label string) error {
+	return fmt.Errorf("not implemented")
+}
+
+func (l *launchd) Stop(label string) error {
+	return fmt.Errorf("not implemented")
+}

internal/daemon/systemd.go

@@ -0,0 +1,23 @@
+package daemon
+
+import (
+	"fmt"
+)
+
+type systemd struct{}
+
+func NewSystemdProvider() DaemonProvider {
+	return &systemd{}
+}
+
+func (s *systemd) Create(config *DaemonConfig, force bool) error {
+	return fmt.Errorf("not implemented")
+}
+
+func (s *systemd) Start(label string) error {
+	return fmt.Errorf("not implemented")
+}
+
+func (s *systemd) Stop(label string) error {
+	return fmt.Errorf("not implemented")
+}