Began work on plugin system

pkg/plugins/plugins.go

@@ -0,0 +1,81 @@
+package plugins
+
+import (
+	"encoding/json"
+	"errors"
+	"os"
+	"path/filepath"
+
+	"github.com/grafana/grafana/pkg/log"
+)
+
+type PluginMeta struct {
+	Type string `json:"type"`
+	Name string `json:"name"`
+}
+
+var (
+	List []*PluginMeta
+)
+
+type PluginScanner struct {
+	pluginPath string
+	errors     []error
+}
+
+func Scan(pluginDir string) error {
+	List = make([]*PluginMeta, 0)
+
+	scanner := &PluginScanner{
+		pluginPath: pluginDir,
+	}
+
+	if err := filepath.Walk(pluginDir, scanner.walker); err != nil {
+		return err
+	}
+
+	if len(scanner.errors) > 0 {
+		return errors.New("Some plugins failed to load")
+	}
+
+	return nil
+}
+
+func (scanner *PluginScanner) walker(path string, f os.FileInfo, err error) error {
+	if err != nil {
+		return err
+	}
+
+	if f.IsDir() {
+		return nil
+	}
+
+	if f.Name() == "plugin.json" {
+		pluginMeta, err := loadPluginMeta(path)
+		if err != nil {
+			log.Error(3, "Failed to load plugin json file: %v,  err: %v", path, err)
+			scanner.errors = append(scanner.errors, err)
+		} else {
+			List = append(List, pluginMeta)
+		}
+	}
+	return nil
+}
+
+func loadPluginMeta(path string) (*PluginMeta, error) {
+	reader, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	defer reader.Close()
+
+	jsonParser := json.NewDecoder(reader)
+
+	pluginMeta := &PluginMeta{}
+	if err := jsonParser.Decode(pluginMeta); err != nil {
+		return nil, err
+	}
+
+	return pluginMeta, nil
+}