load plugins in order of dependencies.

internal/plugins/dependency.go

@@ -0,0 +1,130 @@
+package plugins
+
+import (
+	"fmt"
+
+	"github.com/rs/zerolog"
+
+	"gitlab.com/demodesk/neko/server/pkg/types"
+)
+
+type dependency struct {
+	plugin    types.Plugin
+	dependsOn []*dependency
+	invoked   bool
+	logger    zerolog.Logger
+}
+
+type dependiencies struct {
+	deps   map[string]*dependency
+	logger zerolog.Logger
+}
+
+func (d *dependiencies) addPlugin(plugin types.Plugin) error {
+	plug, ok := d.deps[plugin.Name()]
+	if !ok {
+		plug = &dependency{}
+	} else if plug.plugin != nil {
+		return fmt.Errorf("plugin '%s' already added", plugin.Name())
+	}
+
+	plug.plugin = plugin
+	plug.logger = d.logger
+	d.deps[plugin.Name()] = plug
+
+	dplug, ok := plugin.(types.DependablePlugin)
+	if !ok {
+		return nil
+	}
+
+	for _, dep := range dplug.DependsOn() {
+		var dependsOn *dependency
+		dependsOn, ok = d.deps[dep]
+		if !ok {
+			dependsOn = &dependency{}
+		} else if dependsOn.plugin != nil {
+			// if there is a cyclical dependency, break it and return error
+			if tdep := dependsOn.findPlugin(plugin.Name()); tdep != nil {
+				dependsOn.dependsOn = nil
+				delete(d.deps, plugin.Name())
+				return fmt.Errorf("cyclical dependency detected: '%s' <-> '%s'", plugin.Name(), tdep.plugin.Name())
+			}
+		}
+
+		plug.dependsOn = append(plug.dependsOn, dependsOn)
+		d.deps[dep] = dependsOn
+	}
+
+	return nil
+}
+
+func (d *dependiencies) start(pm types.PluginManagers) error {
+	for _, p := range d.deps {
+		if err := p.start(pm); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (d *dependiencies) findPlugin(name string) (*dependency, bool) {
+	for _, p := range d.deps {
+		if found := p.findPlugin(name); found != nil {
+			return found, true
+		}
+	}
+	return nil, false
+}
+
+func (a *dependency) findPlugin(name string) *dependency {
+	if a == nil {
+		return nil
+	}
+
+	if a.plugin.Name() == name {
+		return a
+	}
+
+	for _, p := range a.dependsOn {
+		if found := p.findPlugin(name); found != nil {
+			return found
+		}
+	}
+
+	return nil
+}
+
+func (d *dependiencies) forEach(f func(*dependency) error) error {
+	for _, dp := range d.deps {
+		if err := f(dp); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (d *dependiencies) len() int {
+	return len(d.deps)
+}
+
+func (a *dependency) start(pm types.PluginManagers) error {
+	if a.invoked {
+		return nil
+	}
+
+	a.invoked = true
+
+	for _, do := range a.dependsOn {
+		if err := do.start(pm); err != nil {
+			return err
+		}
+	}
+
+	err := a.plugin.Start(pm)
+	a.logger.Err(err).Str("plugin", a.plugin.Name()).Msg("plugin start")
+	if err != nil {
+		return fmt.Errorf("plugin %s failed to start: %s", a.plugin.Name(), err)
+	}
+
+	return nil
+}