In ListenerCounter struct also keep track of overall number of listeners for a song and its max simultaneous number of listeners. These parameters are being reset with a Reset() method that returns its values.

internal/radio/listener_counter.go

@@ -3,15 +3,15 @@ package radio
 import (
 	"encoding/json"
 	"errors"
-	"fmt"
 	"math"
 	"sync"
 )
 
-// ListenerCounter stores the current and peak numbers of listeners.
+// ListenerCounter stores the current, overall and peak numbers of listeners.
 type ListenerCounter struct {
 	mutex             sync.RWMutex
 	current, peak     int64
+	overall, cur_peak int64
 }
 
 // NewListenerCounter returns a new ListenerCounter struct instance.
@@ -39,12 +39,19 @@ func (l *ListenerCounter) Inc() int64 {
 	defer l.mutex.Unlock()
 	if l.current == math.MaxInt64 {
 		// We panic here because if this will ever happen, then something's going certainly wrong.
-		panic(fmt.Sprint("a current number of listeners exceeded MaxInt64 which is", math.MaxInt))
+		panic("a current number of listeners exceeded MaxInt64")
 	}
 	l.current++
 	if l.current > l.peak {
 		l.peak = l.current
 	}
+	if l.current > l.cur_peak {
+		l.cur_peak = l.current
+	}
+	if l.overall == math.MaxInt64 {
+		panic("an overall number of listeners exceeded MaxInt64")
+	}
+	l.overall++
 	return l.current
 }
 
@@ -60,13 +67,27 @@ func (l *ListenerCounter) Dec() (int64, error) {
 	return l.current, nil
 }
 
+// Reset current peak and overall listeners for a song that is playing.
+// And return its values.
+func (l *ListenerCounter) Reset() (overall, peak int64) {
+	l.mutex.Lock()
+	defer l.mutex.Unlock()
+	peak = l.cur_peak
+	l.cur_peak = l.current
+	overall = l.overall
+	l.overall = l.current
+	return
+}
+
 func (l *ListenerCounter) MarshalJSON() ([]byte, error) {
 	l.mutex.RLock()
 	defer l.mutex.RUnlock()
 	return json.Marshal(&struct {
 		Current int64 `json:"current"`
 		Peak    int64 `json:"peak"`
+		Overall int64 `json:"overall"`
 	}{
 		Current: l.current,
-		Peak:    l.peak})
+		Peak:    l.peak,
+		Overall: l.overall})
 }