Update ccMetric README and FromMetric copy

internal/ccMetric/README.md

@@ -6,27 +6,52 @@ It is basically a copy of the [InfluxDB line protocol](https://github.com/influx
 
 ```golang
 type ccMetric struct {
-    name   string            // same as
-    tags   []*influx.Tag     // original
-    fields []*influx.Field   // Influx
-    tm     time.Time         // line-protocol
-    meta   []*influx.Tag
+    name   string                 // Measurement name
+    meta   map[string]string      // map of meta data tags
+    tags   map[string]string      // map of of tags
+    fields map[string]interface{} // map of of fields
+    tm     time.Time              // timestamp
 }
 
 type CCMetric interface {
-    influx.MutableMetric        // the same functions as defined by influx.MutableMetric
-    RemoveTag(key string)       // this is not published by the original influx.MutableMetric
-    Meta() map[string]string
-    MetaList() []*inlux.Tag
-    AddMeta(key, value string)
-    HasMeta(key string) bool
-    GetMeta(key string) (string, bool)
-    RemoveMeta(key string)
+    ToPoint(metaAsTags map[string]bool) *write.Point  // Generate influxDB point for data type ccMetric
+    ToLineProtocol(metaAsTags map[string]bool) string // Generate influxDB line protocol for data type ccMetric
+    String() string                                   // Return line-protocol like string
+
+    Name() string        // Get metric name
+    SetName(name string) // Set metric name
+
+    Time() time.Time     // Get timestamp
+    SetTime(t time.Time) // Set timestamp
+
+    Tags() map[string]string                   // Map of tags
+    AddTag(key, value string)                  // Add a tag
+    GetTag(key string) (value string, ok bool) // Get a tag by its key
+    HasTag(key string) (ok bool)               // Check if a tag key is present
+    RemoveTag(key string)                      // Remove a tag by its key
+
+    Meta() map[string]string                    // Map of meta data tags
+    AddMeta(key, value string)                  // Add a meta data tag
+    GetMeta(key string) (value string, ok bool) // Get a meta data tab addressed by its key
+    HasMeta(key string) (ok bool)               // Check if a meta data key is present
+    RemoveMeta(key string)                      // Remove a meta data tag by its key
+
+    Fields() map[string]interface{}                   // Map of fields
+    AddField(key string, value interface{})           // Add a field
+    GetField(key string) (value interface{}, ok bool) // Get a field addressed by its key
+    HasField(key string) (ok bool)                    // Check if a field key is present
+    RemoveField(key string)                           // Remove a field addressed by its key
 }
+
+func New(name string, tags map[string]string, meta map[string]string, fields map[string]interface{}, tm time.Time) (CCMetric, error)
+func FromMetric(other CCMetric) CCMetric
+func FromInfluxMetric(other lp.Metric) CCMetric
 ```
 
-The `CCMetric` interface provides the same functions as the `MutableMetric` like `{Add, Remove, Has}{Tag, Field}` and additionally provides `{Add, Remove, Has}Meta`.
+The `CCMetric` interface provides the same functions as the `MutableMetric` like `{Add, Get, Remove, Has}{Tag, Field}` and additionally provides `{Add, Get, Remove, Has}Meta`.
 
 The InfluxDB protocol creates a new metric with `influx.New(name, tags, fields, time)` while CCMetric uses `ccMetric.New(name, tags, meta, fields, time)` where `tags` and `meta` are both of type `map[string]string`.
 
 You can copy a CCMetric with `FromMetric(other CCMetric) CCMetric`. If you get an `influx.Metric` from a function, like the line protocol parser, you can use `FromInfluxMetric(other influx.Metric) CCMetric` to get a CCMetric out of it (see `NatsReceiver` for an example).
+
+Although the [cc-specifications](https://github.com/ClusterCockpit/cc-specifications/blob/master/interfaces/lineprotocol/README.md) defines that there is only a `value` field for the metric value, the CCMetric still can have multiple values similar to the InfluxDB line protocol.