feat(extensions): implement extensions

ext/extension.go

@@ -0,0 +1,36 @@
+package ext
+
+import (
+	"fmt"
+	"plugin"
+)
+
+type Extension interface {
+	Info() *Info
+	Configure()
+	Enable()
+	Disable()
+}
+
+type Info struct {
+	Name string
+}
+
+func open(extFile string) (Extension, error) {
+	pl, err := plugin.Open(extFile)
+	if err != nil {
+		return nil, err
+	}
+
+	sym, err := pl.Lookup("Extension")
+	if err != nil {
+		return nil, err
+	}
+
+	ex, ok := sym.(Extension)
+	if !ok {
+		return nil, fmt.Errorf("the 'Extension' variable in %s does not implement the Extension interface", extFile)
+	}
+
+	return ex, nil
+}

ext/lifecycle.go

@@ -0,0 +1,9 @@
+package ext
+
+const (
+	LifecycleConfigure = LifecyclePhase(0)
+	LifecycleEnable    = LifecyclePhase(1)
+	LifecycleDisable   = LifecyclePhase(2)
+)
+
+type LifecyclePhase int

ext/registry.go

@@ -0,0 +1,78 @@
+package ext
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type Registry struct {
+	extensions map[string]Extension
+}
+
+func NewRegistry() *Registry {
+	return &Registry{
+		extensions: make(map[string]Extension),
+	}
+}
+
+func (r *Registry) RegisterDir(dir string) error {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return err
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".so") {
+			continue
+		}
+
+		ext, err := open(filepath.Join(dir, entry.Name()))
+		if err != nil {
+			return err
+		}
+
+		if err := r.Register(ext); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (r *Registry) Register(ext Extension) error {
+	extensionName := ext.Info().Name
+	if r.IsRegistered(ext) {
+		return fmt.Errorf("theres already an extension with the name '%s'", extensionName)
+	}
+
+	r.extensions[extensionName] = ext
+	return nil
+}
+
+func (r *Registry) IsRegistered(ext Extension) bool {
+	extensionName := ext.Info().Name
+	_, ok := r.extensions[extensionName]
+	return ok
+}
+
+func (r *Registry) RunLifecyclePhase(phase LifecyclePhase) {
+	for _, ext := range r.extensions {
+		switch phase {
+
+		case LifecycleConfigure:
+			ext.Configure()
+
+		case LifecycleEnable:
+			ext.Enable()
+
+		case LifecycleDisable:
+			ext.Disable()
+
+		default:
+			panic(fmt.Errorf("unknown lifecycle phase with id '%d'", int(phase)))
+
+		}
+	}
+}