plugin: cleaning code and update docs

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

internal/cache/cache_manager.go

@@ -17,6 +17,8 @@ type cacheManager struct {
 	cache    map[string]*string
 }
 
+// GetInstance return the instance of the cache manager that it is
+// a singleton.
 func GetInstance() *cacheManager {
 	return &cacheManager{
 		prefix:   "cache",
@@ -74,6 +76,9 @@ func (instance *cacheManager) addToCache(key string) error {
 	return nil
 }
 
+// IsInCache check if the key is inside the cache and return the result
+// this not include side effect, so if any side effect happens, the function
+// always return false.
 func (instance *cacheManager) IsInCache(key string) bool {
 	if instance.cache != nil {
 		_, ok := instance.cache[key]
@@ -113,6 +118,16 @@ func (instance *cacheManager) PutToCache(key string, value interface{}) error {
 	return instance.addToCache(key)
 }
 
+// PurgeFromCache delete the value from cache with the specified key
+// otherwise return an error.
+func (instance *cacheManager) PurgeFromCache(key string) error {
+	key = instance.buildID(key)
+	if err := db.GetInstance().DeleteValue(key); err != nil {
+		return err
+	}
+	return nil
+}
+
 // CleanCache clean the index from the database
 func (instance *cacheManager) CleanCache() error {
 	for key := range instance.cache {

internal/plugin/metric_interface.go

@@ -1,3 +1,5 @@
+// Package plugin implement all the necessary building blocks to implement
+// an open source metrics.
 package plugin
 
 import (
@@ -6,7 +8,7 @@ import (
 	"github.com/vincenzopalazzo/glightning/glightning"
 )
 
-// mapping the internal id with the name of the metrics.
+// MetricsSupported mapping the internal id with the name of the metrics.
 // the id is passed by the plugin RPC name.
 var MetricsSupported map[int]string
 
@@ -24,40 +26,33 @@ func init() {
 	ChannelDirections[1] = "INCOOMING"
 }
 
-// All the metrics need to respect this interface
+// Metric All the metrics need to respect this interface
 type Metric interface {
-	// return the name of the metric
+	// MetricName return the name of the metric
 	MetricName() *string
 
-	// call this to initialized the metric with node
-	// information if any error occurs, a not nil value is
-	// returned
+	// OnInit initialize the method with node information
 	OnInit(lightning *glightning.Lightning) error
 
-	// Call this method when the close rpc method is called
-	OnClose(msg *Msg, lightning *glightning.Lightning) error
+	// OnStop commit the actual information before exit
+	OnStop(msg *Msg, lightning *glightning.Lightning) error
 
-	// Call this method to make the status of the metrics persistent
+	// MakePersistent make the metric persistent
 	MakePersistent() error
 
-	// Method to store the run a callback to upload the content on the server.
-	// TODO: Use an interface to generalize the client, it can be also a rest api
-	// move accept some interface later.
+	// UploadOnRepo Commit the metric on remote server
 	UploadOnRepo(client *graphql.Client, lightning *glightning.Lightning) error
 
-	// Method to store the run a callback to init the content on the server
-	// the first time that the plugin in ran.
+	// InitOnRepo Init metric on the remote server.
 	InitOnRepo(client *graphql.Client, lightning *glightning.Lightning) error
 
-	// Call this method when you want update all the metrics without
-	// some particular event throw from c-lightning
+	// Update the metric with the last information of the node
 	Update(lightning *glightning.Lightning) error
 
-	// Class this method when you want catch some event from
-	// c-lightning and make some operation on the metrics data.
+	// UpdateWithMsg update the metric with the last information fo the node with some msg info
 	UpdateWithMsg(message *Msg, lightning *glightning.Lightning) error
 
-	// convert the object into a json
+	// ToJSON convert the object into a json
 	ToJSON() (string, error)
 
 	// Migrate to a new version of the metrics, some new version of the plugin
@@ -66,7 +61,7 @@ type Metric interface {
 	Migrate(payload map[string]interface{}) error
 }
 
-// Message struct to pass from the plugin to the metric
+// Msg Message struct to pass from the plugin to the metric
 type Msg struct {
 	// The message is from a command? if not it is nil
 	cmd string

internal/plugin/metrics_one.go

@@ -467,9 +467,7 @@ func (instance *MetricOne) MakePersistent() error {
 	return instance.Storage.StoreMetricOneSnapshot(instance.lastCheck, &instanceJson)
 }
 
-// FIXME: the message is not useful, but we keep it only for future evolution
-// or we will remove it from here.
-func (instance *MetricOne) OnClose(msg *Msg, lightning *glightning.Lightning) error {
+func (instance *MetricOne) OnStop(msg *Msg, lightning *glightning.Lightning) error {
 	log.GetInstance().Debug("On close event on metrics called")
 	//TODO: Check if the values are empty, if yes, try a solution
 	// to avoid to push empty payload.
@@ -493,7 +491,10 @@ func (instance *MetricOne) OnClose(msg *Msg, lightning *glightning.Lightning) er
 	}
 	instance.UpTime = append(instance.UpTime, statusItem)
 	instance.lastCheck = now
-	return instance.MakePersistent()
+	if err := instance.MakePersistent(); err != nil {
+		return err
+	}
+	return nil
 }
 
 // ToJSON Convert the MetricOne structure to a JSON string.
@@ -589,7 +590,6 @@ func (instance *MetricOne) checkChannelInCache(lightning *glightning.Lightning,
 	}
 
 	if nodeInfo == nil {
-		// FIXME: we need some method to update the cache and prefilled at the startup.
 		node, err := lightning.GetNode(channelID)
 		if err != nil {
 			log.GetInstance().Error(fmt.Sprintf("Error in command listNodes in makeChannelsSummary: %s", err))
@@ -935,7 +935,7 @@ func (instance *MetricOne) getChannelInfo(lightning *glightning.Lightning,
 
 			switch forward.Status {
 			case "settled", "offered", "failed":
-				// do nothings
+				// do nothing
 				continue
 			case "local_failed":
 				// store the information about the failure