From 328dbc644e59338b28d21936f76bff7c7dc95a8c Mon Sep 17 00:00:00 2001
From: "Alexander \"Arav\" Andreev" <me@arav.su>
Date: Sat, 30 Sep 2023 23:57:31 +0400
Subject: [PATCH] A struct to hold a number of current and peak listeners was
 added.

---
 internal/radio/listeners.go | 50 +++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 internal/radio/listeners.go

diff --git a/internal/radio/listeners.go b/internal/radio/listeners.go
new file mode 100644
index 0000000..a7bfc3d
--- /dev/null
+++ b/internal/radio/listeners.go
@@ -0,0 +1,50 @@
+package radio
+
+import (
+	"errors"
+	"fmt"
+	"math"
+)
+
+// Listeners stores the current and peak numbers of listeners.
+type Listeners struct {
+	current, peak int
+}
+
+// NewListeners returns a new Listeners struct instance.
+func NewListeners() *Listeners {
+	return &Listeners{}
+}
+
+// Current returns a number of current listeners.
+func (l *Listeners) Current() int {
+	return l.current
+}
+
+// Current returns a number of peak listeners.
+func (l *Listeners) Peak() int {
+	return l.peak
+}
+
+// Inc increments by 1 a current number of listeners and updates a peak number.
+func (l *Listeners) Inc() int {
+	if l.current == math.MaxInt {
+		// We panic here because if this will ever happen, then something's going certainly wrong.
+		panic(fmt.Sprint("a current number of listeners exceeded MaxInt which is", math.MaxInt))
+	}
+	l.current++
+	if l.current > l.peak {
+		l.peak = l.current
+	}
+	return l.current
+}
+
+// Dec decrements by 1 a current number of listeners. An error will occur if
+// a resulting number is less than 0.
+func (l *Listeners) Dec() (int, error) {
+	if l.current == 0 {
+		return l.current, errors.New("an attempt to decrement a number of current listeners down to less than 0")
+	}
+	l.current--
+	return l.current, nil
+}