From 85ecf2d20a19cfd3ae837c5787124c5ef9aa5f14 Mon Sep 17 00:00:00 2001
From: xdrm-brackets <doowap31@gmail.com>
Date: Thu, 8 Nov 2018 13:42:13 +0100
Subject: [PATCH] create generic service manager (systemd only, TODO:init)

---
 internal/ser/common.go  |  9 +++++++++
 internal/ser/errors.go  |  7 +++++++
 internal/ser/loader.go  | 45 +++++++++++++++++++++++++++++++++++++++++
 internal/ser/systemd.go | 31 ++++++++++++++++++++++++++++
 4 files changed, 92 insertions(+)
 create mode 100644 internal/ser/common.go
 create mode 100644 internal/ser/errors.go
 create mode 100644 internal/ser/loader.go
 create mode 100644 internal/ser/systemd.go

diff --git a/internal/ser/common.go b/internal/ser/common.go
new file mode 100644
index 0000000..ff3465f
--- /dev/null
+++ b/internal/ser/common.go
@@ -0,0 +1,9 @@
+package ser
+
+// ServiceManager is the common interface for service managers (systemd, init.d)
+type ServiceManager interface {
+	// Name of executable (to check if installed and for debug)
+	Name() string
+	// Exec a specific action on a service
+	Exec(action, service string) error
+}
diff --git a/internal/ser/errors.go b/internal/ser/errors.go
new file mode 100644
index 0000000..ebd6cf8
--- /dev/null
+++ b/internal/ser/errors.go
@@ -0,0 +1,7 @@
+package ser
+
+import (
+	"errors"
+)
+
+var ErrUnknownAction = errors.New("unknown action")
diff --git a/internal/ser/loader.go b/internal/ser/loader.go
new file mode 100644
index 0000000..4c35168
--- /dev/null
+++ b/internal/ser/loader.go
@@ -0,0 +1,45 @@
+package ser
+
+import (
+	"errors"
+	"os/exec"
+)
+
+var ErrUnknownManager = errors.New("unknown service manager")
+var ErrNoCandidateInstalled = errors.New("no package-manager candidate installed")
+
+// available service managers
+// var available = []string{"systemd", "init"}
+var available = []string{"systemd"}
+
+func Load(_manager string) (ServiceManager, error) {
+
+	// 1. fail if unknown manager
+	known := false
+	for _, mgr := range available {
+		if _manager == mgr {
+			known = true
+			break
+		}
+	}
+	if !known {
+		return nil, ErrUnknownManager
+	}
+
+	// 2. Create manager accordingly
+	var manager ServiceManager
+	switch _manager {
+	case "systemd":
+		manager = new(Systemd)
+	default:
+		return nil, ErrUnknownManager
+	}
+
+	// 2. fail if not installed
+	if exec.Command("which", manager.Name()).Run() == nil {
+		return nil, ErrNoCandidateInstalled
+	}
+
+	return manager, nil
+
+}
diff --git a/internal/ser/systemd.go b/internal/ser/systemd.go
new file mode 100644
index 0000000..0b9e8ed
--- /dev/null
+++ b/internal/ser/systemd.go
@@ -0,0 +1,31 @@
+package ser
+
+import (
+	"os/exec"
+)
+
+type Systemd struct{}
+
+// available actions
+var actions = []string{"enable", "disable", "start", "stop", "reload", "restart"}
+
+func (d Systemd) Name() string { return "systemctl" }
+
+func (d Systemd) Exec(action, service string) error {
+
+	// 1. fail if unknown action
+	known := false
+	for _, act := range actions {
+		if action == act {
+			known = true
+			break
+		}
+	}
+	if !known {
+		return ErrUnknownAction
+	}
+
+	// 2. execute command
+	return exec.Command("systemctl", action, service).Run()
+
+}