Remote plugins plumbing.

Signed-off-by: David Calavera <david.calavera@gmail.com>

plugins/plugins.go

@@ -0,0 +1,86 @@
+package plugins
+
+import (
+	"errors"
+	"sync"
+
+	"github.com/Sirupsen/logrus"
+)
+
+var (
+	ErrNotImplements = errors.New("Plugin does not implement the requested driver")
+)
+
+type plugins struct {
+	sync.Mutex
+	plugins map[string]*Plugin
+}
+
+var storage = plugins{plugins: make(map[string]*Plugin)}
+
+type Manifest struct {
+	Implements []string
+}
+
+type Plugin struct {
+	Name     string
+	Addr     string
+	Client   *Client
+	Manifest *Manifest
+}
+
+func (p *Plugin) activate() error {
+	m := new(Manifest)
+	p.Client = NewClient(p.Addr)
+	err := p.Client.Call("Plugin.Activate", nil, m)
+	if err != nil {
+		return err
+	}
+
+	logrus.Debugf("%s's manifest: %v", p.Name, m)
+	p.Manifest = m
+	return nil
+}
+
+func load(name string) (*Plugin, error) {
+	registry := newLocalRegistry("")
+	pl, err := registry.Plugin(name)
+	if err != nil {
+		return nil, err
+	}
+	if err := pl.activate(); err != nil {
+		return nil, err
+	}
+	return pl, nil
+}
+
+func get(name string) (*Plugin, error) {
+	storage.Lock()
+	defer storage.Unlock()
+	pl, ok := storage.plugins[name]
+	if ok {
+		return pl, nil
+	}
+	pl, err := load(name)
+	if err != nil {
+		return nil, err
+	}
+
+	logrus.Debugf("Plugin: %v", pl)
+	storage.plugins[name] = pl
+	return pl, nil
+}
+
+func Get(name, imp string) (*Plugin, error) {
+	pl, err := get(name)
+	if err != nil {
+		return nil, err
+	}
+	for _, driver := range pl.Manifest.Implements {
+		logrus.Debugf("%s implements: %s", name, driver)
+		if driver == imp {
+			return pl, nil
+		}
+	}
+	return nil, ErrNotImplements
+}